In recent years there has been considerable interest in electrode processes at metal surfaces with alkanethiol monolayers attached to them. One effect of the monolayer is that the electron transfer rate from the redox reagent in solution to the metal (gold or platinum are commonly used) becomes clearly nonadiabatic and the effect of the density of states of the metal on such a rate can be investigated.
\r\n\r\nWe develop a way of writing the wave function of a semi-infinite metal using tight-binding matrix elements and the 'Z-transform', a discrete Laplace transform. Using these k-dependent metal wave functions we calculate the coupling matrix element between the metal and the redox reagent and thus the electron transfer rate constant. We then study the effect of changing the density of electronic states at the Fermi level (DOS) of a metal on the rate of nonadiabatic electron transfer by changing the metal.
\r\n\r\nThe DOS of platinum is about 7.5 times that of gold, the difference being mainly due to the d-band of Pt. Inspite of this difference, the calculated electron transfer rate constant increases only by a factor of about 1.8. Bands which are weakly coupled (e.g., the d-band of Pt in the present case) contribute much less to the rate constant than is suggested by their density of states. Thereby, the rate constant is approximately independent of the density of states in two cases: adiabatic electron transfer and nonadiabatic electron transfer when the extra density of states is due to weakly coupled bands. Our results are in agreement with experiments performed with systems similar to those used in our calculations.
\r\n\r\nWe next employ our method to calculate the temperature dependence of the electronic contribution to the nonadiabatic electron transfer rate constant at metal and semiconductor electrodes. We find that the electronic contribution in metals is proportional to T, and under conditions for the maximum rate constant, that at semiconductor electrodes is also proportional to T, but for different reasons than in the case of metals (Boltzmann statistics and transfer at the conduction band edge for the semiconductor vs. Fermi-Dirac statistics and transfer at the Fermi level, which is far from the band edge, of the metal).
\r\n \r\nOn a different topic, we study the inverse photoemission spectra at metal electrode-liquid interfaces. In such experiments, an electron transfer redox agent was used to inject electrons or holes into a metal and create excited electronic states of the metal. Emission thus occurs in competition with energy loss and radiationless transitions. Some of the excited states decay radiatively and gave a frequency-dependent spectrum. The spectrum may be analysed to probe the electronic structure of the metal above and below its Fermi level. The experimental technique, known in the literature as charge transfer inverse photoemission spectroscopy (CTRIPS), is treated theoretically here.
\r\n\r\nWe give a possible explanation of the data using a model, experimental band structures (from vacuum inverse photemission) and surface states from solution electroreflectance (ER) experiments and propose experiments that could be performed to further clarify the mechanism of electron transfer.
", "doi": "10.7907/KK8A-ZF26", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:3194", "collection": "thesis", "collection_id": "3194", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08222002-162219", "primary_object_url": { "basename": "ack,abs,TOC.pdf", "content": "final", "filesize": 162916, "license": "other", "mime_type": "application/pdf", "url": "/3194/1/ack,abs,TOC.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Electrochemical Sensors Based on DNA-Mediated Charge Transport Chemistry", "author": [ { "family_name": "Boon", "given_name": "Elizabeth Marshall", "orcid": "0000-0003-1891-839X", "clpid": "Boon-Elizabeth-Marshall" } ], "thesis_advisor": [ { "family_name": "Barton", "given_name": "Jacqueline K.", "clpid": "Barton-J-K" } ], "thesis_committee": [ { "family_name": "Tirrell", "given_name": "David A.", "clpid": "Tirrell-D-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "clpid": "Gray-H-B" }, { "family_name": "Barton", "given_name": "Jacqueline K.", "clpid": "Barton-J-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The base pair stack within double helical DNA provides an effective medium for charge transport. The \u03c0-stacked DNA base pairs mediate charge transport chemistry over long molecular distances in a reaction that is exquisitely sensitive to DNA sequence-dependent conformation and dynamics. This sensitivity to minor perturbations in DNA structure and base stacking makes DNA-mediated charge transport chemistry an ideal platform for DNA sensing. Electrochemical methods through DNA-modified electrode surfaces that exploit this sensitivity for efficient biosensing are described. Gold electrodes are modified with DNA double helices and used to monitor the electrochemistry of bound redox-active intercalators. The efficiency of electrochemical reduction of the intercalated redox-probe, in a DNA-mediated reaction, provides an indicator of base stacking within the surface-bound duplexes. Perfectly stacked DNA is capable of mediating the electrochemical reduction, while duplexes containing \u03c0-stacking perturbations, such as single base mismatches, do not support current flow to the intercalator.
\r\n\r\nAll single base mismatches, including thermodynamically stable GT and GA mismatches, as well as many common base damage products can be detected within DNA and DNA/RNA hybrid duplexes using this assay. Moreover, mismatches can be detected as a small percentage of a perfectly matched film, making it possible to detect mutations associated with genetic disorders in only a small fraction of cells. This assay is also compatible with DNA based chip technology. Furthermore, electrochemistry at DNA films is found to provide a novel and sensitive method for probing protein dependent changes in DNA structure and enzymatic reactions.
\r\n\r\nThe efficient transport of charge through self-assembled monolayers of thiol-terminated duplexes on gold therefore offers an extremely sensitive probe for the integrity of DNA sequences. Completely new approaches to single base mismatch detection as well as assaying protein-DNA interactions and reactions on surfaces are now available. This technology is generally applicable as a tool for directly measuring base pair stacking in nucleic acid duplexes.
", "doi": "10.7907/PFXM-7M76", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2867", "collection": "thesis", "collection_id": "2867", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-07132001-180811", "primary_object_url": { "basename": "Thesis_Black.pdf", "content": "final", "filesize": 4145688, "license": "other", "mime_type": "application/pdf", "url": "/2867/1/Thesis_Black.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Electrical Properties of Nanoscale Parallel Semiconductor Interfaces", "author": [ { "family_name": "Rossi", "given_name": "Robert Charles", "clpid": "Rossi-Robert-Charles" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Tirrell", "given_name": "David A.", "orcid": "0000-0003-3175-4596", "clpid": "Tirrell-D-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Nanosphere lithography has been used to prepare a series of ordered, periodic arrays of low barrier height n-Si/Ni nanometer-scale contacts interspersed amongst high barrier height n-Si/liquid contacts. To form the arrays, crystalline bilayers of close-packed latex spheres were deposited onto (100)-oriented n-type single crystal Si surfaces. The spheres formed a physical mask through which Ni was evaporated to produce regularly spaced and regularly sized Si/Ni contacts. By varying the diameter of the latex spheres from 174 nm to 1530 nm, geometrically self-similar Si/Ni structures were produced having triangular Si/Ni regions with edge dimensions of 100 - 800 nm. The resulting Si surfaces were used as electrodes in contact with a methanolic solution of LiClO4 and 1,1'-dimethylferrocene/1,1'-dimethylferrocenium. The current-voltage and photoresponse properties of these mixed barrier height contacts were strongly dependent on the size of the Ni regions, even though the fraction of the Si surface covered by Ni remained constant. Electrodes formed from large-dimension Si/Ni and Si/electrolyte contacts behaved as expected for two area-weighted Schottky diodes operating independently and in parallel, whereas electrodes having nanoscale Si/Ni and Si/liquid contacts behaved in quantitative accord with effective barrier height theories that predict a \"pinch-off\" effect for mixed barrier height systems of sufficiently small physical dimensions.\r\n", "doi": "10.7907/F9YE-BM08", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6805", "collection": "thesis", "collection_id": "6805", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02022012-100419178", "primary_object_url": { "basename": "Liu_z_2002.pdf", "content": "final", "filesize": 3931157, "license": "other", "mime_type": "application/pdf", "url": "/6805/1/Liu_z_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Vanadium-Schiff Base Complexes as Catalysts for the Four-Electron Reduction of Dioxygen", "author": [ { "family_name": "Liu", "given_name": "Zenghe", "clpid": "Liu-Zhenghe" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "clpid": "Marcus-R-A" }, { "family_name": "Peters", "given_name": "Jonas C.", "clpid": "Peters-J-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The coordination chemistry and electrochemistry of complexes of vanadium(III, IV, V) with salen (H_2salen = N,N'-ethylenebis(salicylideneamine)) were first examined. The origin of the puzzling results reported in previous reports in the literature was identified using\r\nmicroelectrode voltammetry and the modifications required are specified. VO(salen) was found to disproportionate in acidified acetonitrile. The equilibrium constant for this disproportionation reaction was measured. The stoichiometry and kinetics of the reaction between O_2 and the V(III)salen\r\ncomplex were examined and a possible mechanism for this four-electron reduction of O_2 is suggested.
\r\nThe study was then expanded to vanadium complexes with fifteen Schiff base (SB) ligands analogous to salen. Electrochemical and spectral characteristics of the complexes were evaluated and compared. With several of the ligands the V(III) complexes are much more stable in\r\nthe presence of acid than is the complex with salen. Equilibrium constants for the disproportionation of the oxovanadium (IV) complexes were evaluated. The vanadium(III) complexes reduce dioxygen to form two oxo ligands. In the presence of acid some of the complexes\r\ninvestigated participate in a catalytic electroreduction of dioxygen.
\r\nThe otherwise slow reaction between O_2 and decamethylferrocene or V^(III)(SB)^+ is significantly accelerated if these three reactants are present. In the absence of acid the reduction of O_2 proceeds stoichiometrically to yield the two oxo groups in (SB)V^(IV)O. In the presence of acid the reaction becomes catalytic and the O_2 is reduced to H_2O. Preliminary results on the kinetics of the O_2 reduction was presented.
\r\nElectrochemical study on vanadium-naphophen (naphophen = N, N'-1, 2-phenylenebis-(2-hydroxy-l-naphthylideneiminate)) complexes in acetonitrile containing excess acetic anhydride was also conducted. V^(IV)O(naphophen) was found to undergo deoxygenation by two equivalents of acid to give V^(IV)(naphophen)^(2+), which had not persisted in\r\nprevious study. Several reactions proposed previously to describe the chemistry of vanadium-Schiff base complexes in acetonitrile were directly demonstrated with this species.
\r\nThe oxovanadium-naphophen complexes were found to\r\nspontaneously adsorb on EPG electrodes. They also exhibited\r\nremarkable stability towards acid after adsorption. Their surface electrochemical behavior was studied and characterized using cyclic voltammetry.
\r\n\r\n", "doi": "10.7907/BV5W-DK24", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:8146", "collection": "thesis", "collection_id": "8146", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03192014-125137237", "primary_object_url": { "basename": "Gao-yq-2001.pdf", "content": "final", "filesize": 30151528, "license": "other", "mime_type": "application/pdf", "url": "/8146/1/Gao-yq-2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Theory of Ozone Isotopic Effects and Various Electron Transfer Reaction", "author": [ { "family_name": "Gao", "given_name": "Yi Qin", "clpid": "Gao-Yi-Qin" } ], "thesis_advisor": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" } ], "thesis_committee": [ { "family_name": "Kuppermann", "given_name": "Aron", "clpid": "Kuppermann-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Three separate topics, each stimulated by experiments, are treated theoretically in this dessertation: isotopic effects of ozone, electron transfer at interfaces, and intramolecular directional electron transfer in a supramolecular system.
\r\n\r\nThe strange mass-independent isotope effect for the enrichment of ozone, which has been a puzzle in the literature for some 20 years, and the equally puzzling unconventional strong mass-dependent effect of individual reaction rate constants are studied as different aspects of a symmetry-driven behavior. A statistical (RRKM-based) theory with a hindered-rotor transition state is used. The individual rate constant ratios of recombination reactions at low pressures are calculated using the theory involving (1) small deviation from the statistical density of states for symmetric isotopomers, and (2) weak collisions for deactivation of the vibrationally excited ozone molecules. The weak collision and partitioning among exit channels play major roles in producing the large unconventional isotope effect in \"unscrambled\" systems. The enrichment studies reflect instead the non-statistical effect in \"scrambled\" systems. The theoretical results of low-pressure ozone enrichments and individual rate constant ratios obtained from these calculations are consistent with the corresponding experimental results. The isotopic exchange rate constant for the reaction ^(16)O + ^(18)O ^(18)O\u2192+ ^(16)O ^(18)O + ^(18)O provides information on the nature of a variationally determined hindered-rotor transition state using experimental data at 130 K and 300 K. Pressure effects on the recombination rate constant, on the individual rate constant ratios and on the enrichments are also investigated. The theoretical results are consistent with the experimental data. The temperature dependence of the enrichment and rate constant ratios is also discussed, and experimental tests are suggested. The desirability of a more accurate potential energy surface for ozone in the transition state region is also noted.
\r\n\r\nElectron transfer reactions at semiconductor /liquid interfaces are studied using a tight-binding model for the semiconductors. The slab method and a z-transform\r\nmethod are employed in obtaining the tight-binding electronic structures of semiconductors having surfaces. The maximum electron transfer rate constants at Si/viologen^(2-/+) and InP /Me_(2)Fc^(+/O) interfaces are computed using the tight-binding type calculations for the solid and the extended-Huckel for the coupling to the redox agent at the interface. These electron transfer reactions are also studied using a free electron model for the semiconductor and the redox molecule, where Bardeen's method is adapted to calculate the coupling matrix element between the molecular and semiconductor electronic states. The calculated results for maximum rate constant of the electron transfer from the semiconductor bulk states are compared with the experimentally measured values of Lewis and coworkers, and are in reasonable agreement, without adjusting parameters. In the case of InP /liquid interface, the unusual current vs applied potential behavior is additionally interpreted, in part, by the presence of surface states.
\r\n\r\nPhotoinduced electron transfer reactions in small supramolecular systems, such as 4-aminonaphthalimide compounds, are interesting in that there are, in principle,\r\ntwo alternative pathways (directions) for the electron transfer. The electron transfer, however, is unidirectional, as deduced from pH-dependent fluorescence quenching studies on different compounds. The role of electronic coupling matrix element and the charges in protonation are considered to explain the directionality of the electron transfer and other various results. A related mechanism is proposed to interpret the fluorescence behavior of similar molecules as fluorescent sensors of metal ions.
\r\n", "doi": "10.7907/fj7v-ht75", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:3255", "collection": "thesis", "collection_id": "3255", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08282001-123851", "primary_object_url": { "basename": "JGK_Thesis_for_DBLsided_printing.pdf", "content": "final", "filesize": 3984594, "license": "other", "mime_type": "application/pdf", "url": "/3255/1/JGK_Thesis_for_DBLsided_printing.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Probing Quantum Confinement at the Atomic Scale with Optically Detected Nuclear Magnetic Resonance", "author": [ { "family_name": "Kempf", "given_name": "James G.", "clpid": "Kempf-James-G" } ], "thesis_advisor": [ { "family_name": "Weitekamp", "given_name": "Daniel P.", "orcid": "0000-0003-0079-8000", "clpid": "Weitekamp-D-P" } ], "thesis_committee": [ { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Kuppermann", "given_name": "Aron", "clpid": "Kuppermann-A" }, { "family_name": "Weitekamp", "given_name": "Daniel P.", "orcid": "0000-0003-0079-8000", "clpid": "Weitekamp-D-P" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Near-band-gap circularly polarized excitation in III-V semiconductors provides spin-polarized electrons that transfer spin order to lattice nuclei via fluctuations in the contact hyperfine interaction. This process of optical nuclear polarization and the complementary technique of optical detection of nuclear magnetic resonance (NMR) provide extreme sensitivity enhancement and spatial selectivity in structured samples, enabling collection of NMR spectra from samples such as single quantum wells or dots containing as few as ~10^5 nuclei.
\r\n\r\nCombining these advances with novel techniques for high spectral resolution, we have probed quantum-confined electronic states near the interface of a single epitaxially grown Al(1-x)Ga(x)As/GaAs (x = 0.36) heterojunction. Using a novel strategy that we refer to as POWER (perturbations observed with enhanced resolution) NMR, multiple-pulse time suspension is synchronized with bandgap optical irradiation to reveal spectra of effective spin Hamiltonians that are differences between those of the occupied and unoccupied photoexcited electronic state. The underlying NMR linewidth is reduced by three orders of magnitude in these experiments, enabling resolution of an asymmetric line shape due to light-induced hyperfine interactions. The results are successfully fit with the coherent nuclear spin evolution and relaxation theoretically expected for sites distributed over the volume of an electronic excitation weakly localized at a point defect. This analysis establishes a one-to-one relationship, which can be used to follow nuclear spin diffusion, between optical Knight shift and the radial position of lattice nuclei.
\r\n\r\nWe have also introduced POWER NMR techniques to characterize the change in electric field associated with cycling from light-on to light-off states via a linear quadrupole Stark effect (LQSE) of the nuclear spins. Simulations of these NMR spectra in terms of the radial electric fields of either donor-bound electrons or excitons indicate differences, where the bound-exciton model provides a significantly better fit to the data. The same spin physics enabled our measurement of the heterojunction interfacial field, which we find to be less than 1.3 kV/cm at the sites responsible for optical NMR. Other simulations show the promise of optical NMR as a tool in future studies aimed at atomic-level characterization of quantum-confined systems such as quantum dots and wells.
", "doi": "10.7907/0JZB-N948", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:8181", "collection": "thesis", "collection_id": "8181", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04072014-140228693", "primary_object_url": { "basename": "Yoder_jc_2001.pdf", "content": "final", "filesize": 36660534, "license": "other", "mime_type": "application/pdf", "url": "/8181/1/Yoder_jc_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Model Studies of Ziegler-Natta Olefin Polymerization Using Group 3 and Group 4 Metallocenes", "author": [ { "family_name": "Yoder", "given_name": "Jeffrey Charles", "clpid": "Yoder-Jeffrey-Charles" } ], "thesis_advisor": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Tirrell", "given_name": "David A.", "orcid": "0000-0003-3175-4596", "clpid": "Tirrell-D-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Evidence for the stereochemical isomerization of a variety of ansa\r\nmetallocene compounds is presented. For the scandocene allyl derivatives\r\ndescribed here, we have established that the process is promoted by a variety of\r\nsalts in both ether and hydrocarbon solvents and is not accelerated by light. A\r\nplausible mechanism based on an earlier proposal by Marks, et al., is offered as\r\nan explanation of this process. It involves coordination of anions and/or donor\r\nsolvents to the metal center with cation assistance to encourage metalcyclopentadienyl\r\nbond heterolysis, rotation about the Si-Cp bond of the\r\ndetached cyclopentadienide and recoordination of the opposite face. Our\r\nobservations in some cases of thermodynamic racemic:meso ratios under the\r\nreaction conditions commonly used for the synthesis of the metallocene\r\nchlorides suggests that the interchange is faster than metallation, such that the\r\ncomposition of the reaction mixture is determined by thermodynamic, not\r\nkinetic, control in these cases.
\r\n\r\nTwo new ansa-scandocene alkenyl compounds react with olefins resulting\r\nin the formation of \u03b73-allyl complexes. Kinetics and labeling experiments\r\nindicate a tuck-in intermediate on the reaction pathway; in this intermediate the\r\nmetal is bound to the carbon adjacent to the silyllinker in the rear of the\r\nmetallocene wedge. In contrast, reaction of permethylscandocene alkenyl\r\ncompounds with olefins results, almost exclusively, in vinylic C-H bond\r\nactivation. It is proposed that relieving transition state steric interactions\r\nbetween the cyclopentadienyl rings and the olefin by either linking the rings\r\ntogether or using a larger lanthanide metal may allow for olefin coordination,\r\nstabilizing the transition state for allylic \u03c3-bond metathesis.
\r\n\r\nA selectively isotopically labeled propylene, CH2CD(13CH3), was\r\nsynthesized and its polymerization was carried out at low concentration in\r\ntoluene solution using isospecific metallocene catalysts. Analysis of the NMR\r\nspectra (13C, 1H, and 2H) of the resultant polymers revealed that the production\r\nof stereoerrors through chain epimerization proceeds exclusively by the tertiaryalkyl\r\nmechanism. Additionally, enantiofacial inversion of the terminally\r\nunsaturated polymer chain occurs by a non-dissociative process. The\r\nimplications of these results on the mechanism of olefin polymerization with\r\nthese catalysts is discussed.
", "doi": "10.7907/6qry-9x55", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:8167", "collection": "thesis", "collection_id": "8167", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03252014-134849293", "primary_object_url": { "basename": "ZHONG 2001.pdf", "content": "final", "filesize": 53986796, "license": "other", "mime_type": "application/pdf", "url": "/8167/1/ZHONG 2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Ancillary Ligand Effects: From Zirconium(IV)-Catalyzed Homogeneous Propylene Polymerization to Platinum(II)-Mediated C-H Bond Activation", "author": [ { "family_name": "Zhong", "given_name": "Hong A.", "clpid": "Zhong-Hong-A" } ], "thesis_advisor": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "MacMillan", "given_name": "David W. C.", "orcid": "0000-0003-3352-4532", "clpid": "MacMillan-D-W-C" }, { "family_name": "Labinger", "given_name": "Jay A.", "orcid": "0000-0002-1942-9232", "clpid": "Labinger-J-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A series of Cs- and C1-symmetric doubly-linked ansa-metallocenes of the general formula {1,1'-SiMe2-2,2'-E-('\u019e5-C5H2-4-R1)-(\u019e5-C5H-3',5'-(CHMe2)2)}ZrC2 (E = SiMe2 (1), SiPh2 (2), SiMe2 -SiMe2 (3); R1 = H, CHMe2, C5H9, C6H11, C6H5) has been prepared. When activated by methylaluminoxane, these are active propylene polymerization catalysts. 1 and 2 produce syndiotactic polypropylenes, and 3 produces isotactic polypropylenes. Site epimerization is the major pathway for stereoerror formation for 1 and 2. In addition, the polymer chain has slightly stronger steric interaction with the diphenylsilylene linker than with the dimethylsilylene linker. This results in more frequent site epimerization and reduced\r\nsyndiospecificity for 2 compared to 1.
\r\n\r\nC1-Symmetric ansa-zirconocenes [1,1 '-SiMe2-(C5H4)-(3-R-C5H3)]ZrCl2 (4), [1,1 '-SiMe2-(C5H4)-(2,4-R2-C5H2)]ZrCl2 (5) and [1,1 '-SiMe2-2,2 '-(SiMe2-SiMe2)-(C5H3)-( 4-R-C5H2)]ZrCl2 (6) have been prepared to probe the origin of isospecificity in 3. While 4 and 3 produce polymers with similar isospecificity, 5 and 6 give mostly hemi-isotactic-like polymers. It is proposed that the facile site epimerization via an associative pathway allows rapid equilibration of the polymer chain between the isospecific and aspecific insertion sites. This results in more frequent insertion from the isospecific site, which has a lower kinetic barrier for chain propagation. On the other hand, site epimerization for 5 and 6 is slow. This leads to mostly alternating insertion from the isospecific and aspecific sites, and consequently, a hemi-isotactic-like polymers. In comparison, site epimerization is even slower for 3, but enchainment from the aspecific site has an extremely high kinetic barrier for monomer coordination. Therefore, enchainment occurs preferentially from the isospecific site to produce isotactic polymers.
\r\n\r\nA series of cationic complexes [(ArN=CR-CR=NAr)PtMe(L)]+[BF4]+ (Ar = aryl; R = H, CH3; L = water, trifluoroethanol) has been prepared. They react smoothly with benzene at approximately room temperature in trifluoroethanol solvent to yield methane and the corresponding phenyl Pt(II) cations, via Pt(IV)-methyl-phenyl-hydride intermediates. The reaction products of methyl-substituted benzenes suggest an inherent reactivity preference for aromatic over benzylic C-H bond activation, which can however be overridden by steric effects. For the reaction of benzene with cationic Pt(II) complexes, in which the diimine ligands bear 3,5-disubstituted aryl groups at the nitrogen atoms, the rate-determining step is C-H bond activation. For the more sterically crowded analogs with 2,6-dimethyl-substituted aryl groups, benzene coordination becomes rate-determining. The more electron-rich the ligand, as reflected by the CO stretching frequency in the IR spectrum of the corresponding cationic carbonyl complex, the faster the rate of C-H bond activation. This finding, however, does not reflect the actual C-H bond activation process, but rather reflects only the relative ease of solvent molecules displacing water molecules to initiate the reaction. That is, the change in rates is mostly due to a ground state effect. Several lines of evidence suggest that associative substitution pathways operate to get the hydrocarbon substrate into, and out of, the coordination sphere; i.e., that benzene substitution proceeds by a solvent- (TFE-) assisted associative pathway.
\r\n", "doi": "10.7907/km2k-bb61", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:8152", "collection": "thesis", "collection_id": "8152", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03202014-115036901", "primary_object_url": { "basename": "Rostovtsev 2001.pdf", "content": "final", "filesize": 26833972, "license": "other", "mime_type": "application/pdf", "url": "/8152/1/Rostovtsev 2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Reactions of Platinum(II) Complexes with Dioxygen: Progress Toward Alkane Functionalization", "author": [ { "family_name": "Rostovtsev", "given_name": "Vsevolod Vladimirovich", "orcid": "0000-0002-1226-5909", "clpid": "Rostovtsev-Vsevolod-Vladimirovich" } ], "thesis_advisor": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Labinger", "given_name": "Jay A.", "orcid": "0000-0002-1942-9232", "clpid": "Labinger-J-A" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Whereas stoichiometric activation of C-H bonds by complexes of transition metals is\r\nbecoming increasingly common, selective functionalization of alkanes remains a\r\nformidable challenge in organometallic chemistry. The recent advances in catalytic\r\nalkane functionalization by transition-metal complexes are summarized in Chapter I.
\r\n\r\nThe studies of the displacement of pentafluoropyridine in\r\n[(tmeda)Pt(CH_3)(NC_5F_5)][BAr^f_4] (1) with \u03b3- tetrafluoropicoline, a very poor nucleophile,\r\nare reported in Chapter II. The ligand substitution occurs by a dissociative interchange\r\nmechanism. This result implies that dissociative loss of pentafluoropyridine is the rate-limiting\r\nstep in the C-H activation reactions of 1.
\r\n\r\nOxidation of dimethylplatinum(II) complexes (N-N)Pt(CH_3)_2 (N-N = tmeda(1), \u03b1-diimines)\r\nby dioxygen is described in Chapter III. Mechanistic studies suggest a two-step mechanism. First, a hydroperoxoplatinum(IV) complex is formed in a reaction\r\nbetween (N-N)Pt(CH_3)_2 and dioxygen. Next, the hydroperoxy complex reacts with a\r\nsecond equivalent of (N-N)Pt(CH_3)_2 to afford the final product,\r\n(N-N)Pt(OH)(OCH_3)(CH_3)_2. The hydroperoxy intermediate,\r\n(tmeda)Pt(OOH)(OCH_3)(CH_3)_2 (2), was isolated and characterized. The reactivity of 2\r\nwith several dime thylplatinum(II) complexes is reported.
\r\n\r\nThe studies described in Chapter IV are directed toward the development of a\r\nplatinum(II)-catalyzed oxidative alkane dehydrogenation. Stoichiometric conversion of\r\nalkanes (cyclohexane, ethane) to olefins (cyclohexene, ethylene) is achieved by C-H\r\nactivation with [(N-N)Pt(CH_3)(CF_3CH_2OH)]BF_4 (1, N-N is N,N'-bis(3,5-di-t-\r\nbutylphenyl)-1,4-diazabutadiene) which results in the formation of olefin hydride\r\ncomplexes. The first step in the C-H activation reaction is formation of a platinum(II)\r\nalkyl which undergoes \u03b2-hydrogen elimination to afford the olefin hydride complex.\r\nThe cationic ethylplatinum(II) intermediate can be generated in situ by treating\r\ndiethylplatinum(II) compounds with acids. Treatment of (phen)PtEt_2 with\r\n[H(OEt_2)_2]Bar^f_4 at low temperatures resulted in the formation of a mixture of\r\n[(phen)PtEt(OEt_2)]Bar^f_4 (8) and [(phen)Pt(C_2H_4)H] Bar^f_4 (7). The cationic olefin\r\ncomplexes are unreactive toward dioxygen or hydrogen peroxide. Since the success of\r\nthe overall catalytic cycle depends on our ability to oxidize the olefin hydride\r\ncomplexes, a series of neutral olefin complexes of platinum(II) with monoanionic ligands\r\n(derivatives of pyrrole-2-carboxyaldehyde N-aryl imines) was prepared. Unfortunately,\r\nthese are also stable to oxidation.
\r\n", "doi": "10.7907/jevj-7928", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:4490", "collection": "thesis", "collection_id": "4490", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11102005-103556", "primary_object_url": { "basename": "Lai_r_2001.pdf", "content": "final", "filesize": 4700896, "license": "other", "mime_type": "application/pdf", "url": "/4490/1/Lai_r_2001.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Synthesis and Characterization of ZSM-5 Zeolite Membranes", "author": [ { "family_name": "Lai", "given_name": "Re", "clpid": "Lai-Re" } ], "thesis_advisor": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Davis", "given_name": "Mark E.", "orcid": "0000-0001-8294-1477", "clpid": "Davis-M-E" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Synthesis of ZSM-5 zeolite membranes supported on porous alumina substrates was conducted in autoclave reactors. The film morphologies and structures were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Gas adsorption was used to estimate the crystalline fraction of the products. The gas permeation properties of the membranes were evaluated for H\u2082, CH\u2084, O\u2082, N\u2082, and n-butane and other gases singly or in mixtures.
\r\n\r\nZSM-5 film formation on alumina and other surfaces in certain clear, tetrapropylammonium(TPA\u207a)-containing synthesis solutions was found to be preceded by a gel layer. The presence of alumina and other substrates of a high Hamaker constant facilitated formation of the surface gel layer and accelerated zeolite crystallization. Aluminum added to the solution or leached from alumina substrates had dual effects, to induce surface gelation and to retard crystallization of that layer as well as crystallization in the bulk solution.
\r\n\r\nGrowth of ZSM-5 membranes was facilitated by using alumina tubes pre-coated with silicalite seeds. Accompanied with gradual growth of an external polycrystalline layer, siliceous deposits accumulated as deep as 100 \u00b5m inside the pores of the support, converting gradually from amorphous to crystalline. Pure gas permeation results are presented for membranes prepared in a solution of composition SiO\u2082: 0.15TPAB4: 0.7NaOH: 98H\u2082O using 0.4 and 2 \u00b5m seeds.
\r\n\r\nOrganic-free hydrogel reaction mixtures were further used to grow ZSM-5 membranes on seeded porous alumina substrates, eliminating the crack-prone calcination step for removing organic TPA\u207a templates from as-synthesized ZSM-5. The optimum composition SiO\u2082: 0.0125Al\u2082O\u2083: 0.2675Na\u2082O: 46H\u2082O was identified to produce membranes with permeation selectivities for H\u2082 over n-butane above 10\u2074 and for O\u2082 over N\u2082 9-10. The permeation was strongly activated with the activation energies increasing sharply with molecular size.
\r\n\r\nParallel synthesis of zeolite films was developed to expedite composition screening. The films prepared in an array reactor of multiple wells each containing 35 micro-liter synthesis solution displayed morphology similar to that produced by the conventional synthesis. The method was applied to explore the composition space of clear, organic-free synthesis solutions for ZSM-5 films growth: SiO\u2082: (700-300)Al\u2082O\u2083: (0.5-0.7)NaOH: 80H\u2082O.
", "doi": "10.7907/m5xs-mq20", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:17634", "collection": "thesis", "collection_id": "17634", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08192025-174058689", "primary_object_url": { "basename": "Wang_G_1999.pdf", "content": "final", "filesize": 50451000, "license": "other", "mime_type": "application/pdf", "url": "/17634/1/Wang_G_1999.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Design and Synthesis of Photoreleasable Ubiquinol and its Biologically Active Analogues", "author": [ { "family_name": "Wang", "given_name": "Guangyang", "clpid": "Wang-Guangyang" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Rees", "given_name": "Douglas C.", "orcid": "0000-0003-4073-1185", "clpid": "Rees-D-C" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Every organism contains a respiratory chain that converts energy from food\r\nmolecules into adenosine triphosphate (ATP) which drives a multitude of biochemical\r\nreactions. A respiratory chain achieves this via a series of integral membrane protein\r\ncomplexes that produce a transmembrane proton gradient as a result of sequential\r\nelectron transfers through these complexes. Ubiquinol and ubiquinol oxidase enzymes are\r\nimportant components of the respiratory chains in most aerobic organisms. The energy\r\nfrom the oxidation of ubiquinol is used to promote the generation of an electrochemical\r\ngradient across the cytoplasmic or mitochondrial membrane for ATP synthesis.
\r\n\r\nStudy of the catalytic mechanisms of ubiquinol oxidase enzymes is very difficult\r\ndue to the structural complexity of these proteins. Since electron input from ubiquinol\r\nplays a very important role in enzyme function, to understand the detailed enzymatic\r\nmechanism of these enzymes, it is critical to understand the kinetics of individual\r\nelectron transfer events in enzymatic turnover. On account of the rapidity of electron\r\ntransfer in these proteins, traditional stopped-flow methods for following the kinetic\r\ncourse of electron transfer reactions are limited, due to the millisecond order of mixing\r\ndead time.
\r\n\r\nPhotochemical initiation of ubiquinol release, a method of circumventing the\r\nmixing limitation, is investigated. The method is based on the photolysis of small\r\norganic protecting groups, or \"cage\" compounds. These cage compounds rendered\r\ninactive quinol-cage complex prior to photolysis by linking to the key functional groups\r\nin ubiquinol or by generating a large steric hindrance that blocks ubiquinol binding.\r\nPhotolysis of the cage-quinol complex rapidly releases the two-electron donor and\r\ntriggers on the enzymatic electron transfer. Such a complex can be used not only in\r\nenzymatic electron transfer study, but also in time-resolved protein conformation change\r\nstudy.
\r\n\r\nThe cage compounds that have been studied for this purpose are based on 3',5'-\r\ndimethoxybenzoin (DMB). Esters of DMB are known to photolyze rapidly (on the sub-nanosecond\r\ntime scale), generating the parent acid and the inert photoproduct 5,7-\r\ndimethoxy-2-phenylbenzofuran. A water-soluble derivative of 3', 5'-dimethoxybenzoin\r\n(DMB),3',5'-bis (carboxylmethoxy)benzoin (BCMB) was linked to the hydroxy group\r\nin ubiquinol via a carbonate linkage. Such a complex has been measured to yield a\r\nphotorelease rate of \r\n990s-1 in detergent solution. Another cage compound, N-hydroxypyridine-\r\n2-thione, was also used to \"cage\" ubiquinol via a carbonate linkage. In\r\nthe presence of efficient hydrogen donor, such as mercaptoethanol, such a complex has\r\nthe potential to photolytically generate ubiquinol in sub-millisecond time scale.
\r\n\r\nA series of ubiquinol analogues were synthesized with a carboxylic acid\r\nfunctionality attached to benzoquinone at different positions. These analogues can be\r\n\"caged\" by BCMB via an ester bond with the potential to trigger electron transfer in sub-microsecond.
\r\n\r\nIn the mean time, efforts have been made to elucidate the controversial photolysis\r\nmechanisms of benzoin compounds by synthetic substitution study and quantum\r\nchemistry calculation. Very efficient synthetic schemes for the preparation of large-size\r\ncombinatorial libraries of benzoins were developed.
", "doi": "10.7907/str8-et07", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:7206", "collection": "thesis", "collection_id": "7206", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09172012-133347649", "primary_object_url": { "basename": "Doleman_bj_1999.pdf", "content": "final", "filesize": 25978440, "license": "other", "mime_type": "application/pdf", "url": "/7206/1/Doleman_bj_1999.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Study and development of an \"electronic nose\" and comparison with mammalian olfaction", "author": [ { "family_name": "Doleman", "given_name": "Brett James", "clpid": "Doleman-B-J" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "clpid": "Lewis-N-S" }, { "family_name": "Barton", "given_name": "Jacqueline K.", "clpid": "Barton-J-K" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "clpid": "Marcus-R-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Arrays of broadly responsive vapor detectors (i.e., electronic noses) are receiving\r\nan increasing amount of scientific attention for their potential as analytical devices, as\r\nmodels for studying mammalian olfaction, and perhaps for someday ultimately duplicating\r\nor surpassing the mammalian olfactory sense. Herein, research was primarily focused on\r\nan electronic nose composed of an array of carbon black-polymer composite detectors\r\nwhile arrays of tin oxide detectors and organic conducting polymer detectors were used\r\nonly in a comparison study. The research determined the odorant resolving power of\r\nelectronic nose sensor arrays, explored the dependence of the electronic nose array\r\nresponse intensity on odorant vapor pressure, compared the odorant detection thresholds\r\nand odorant classification properties of the electronic nose to the mammalian olfactory\r\nsense, and attempted to predict human odor quality judgements using electronic nose\r\ndetector responses.
\r\n\r\nThe Fisher linear discriminant statistical metric was utilized to quantify the\r\nperformance of arrays composed of carbon black-insulating polymer composite detectors,\r\ntin oxide detectors and bulk conducting organic polymer detectors in resolving nineteen\r\nodorant vapors. The odorant resolving power of the sensor arrays as a function of the\r\nchemical composition of the detectors and the number of detectors they contained was\r\nstudied. The results provided insights into optimizing the chemical diversity and size of a\r\nchemical vapor sensor array for various tasks.
\r\n\r\nResponse data were collected for a carbon black-polymer composite electronic nose\r\narray during exposure to homologous series of 1-alcohol and n-alkane odorants. The mean\r\nresponse intensity of the electronic nose detectors, and the response intensity of the most\r\nstrongly-driven set of electronic nose detectors, was essentially constant for members of a\r\nchemically homologous odorant series when the concentration of each odorant in the gas\r\nphase was maintained at a constant fraction of the odorant's vapor pressure. A similar\r\ntrend is observed in human odor detection threshold values for these same odorants. The\r\ndata imply that the trends in detector responses and human detection thresholds can be\r\nunderstood based on the thermodynamic tendency to establish a relatively constant\r\nconcentration of sorbed odorant into each of the polymeric films of the electronic nose and\r\ninto the olfactory epithelium of humans at a constant fraction of the odorant's vapor\r\npressure.
\r\n\r\nExperiments were performed to compare the detection thresholds and trends in\r\ndiscrimination abilities of the electronic nose to those of the mammalian olfactory sense,\r\nand to develop models predicting human odor quality judgements from electronic nose\r\ndetector responses. The detection thresholds for the electronic nose and the human nose\r\nwere compared for series of n-alkanes and 1-alcohols. Trends in the odorant-discriminating\r\nabilities of an electronic nose and mammalian noses were compared for\r\nseries of esters, alcohols and carboxylic acids. Electronic nose response data were\r\ncollected for a diverse set of odorants which had previously been quantitatively\r\ncharacterized by human panelists according to many categories of odor quality. The\r\nresponses of the electronic nose detectors were then used in attempts at predicting the\r\nhuman odor quality judgements.
", "doi": "10.7907/R6QQ-NX09", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:14500", "collection": "thesis", "collection_id": "14500", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02162022-191638374", "primary_object_url": { "basename": "On_the_theory_of_electron_tran.pdf", "content": "final", "filesize": 8192248, "license": "other", "mime_type": "application/pdf", "url": "/14500/1/On_the_theory_of_electron_tran.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "On the Theory of Electron Transfer Reactions: Superexchange Coupling and Polar Solvation Dynamics", "author": [ { "family_name": "Hsu", "given_name": "Chao-Ping", "orcid": "0000-0002-7187-427X", "clpid": "Hsu-Chao-Ping" } ], "thesis_advisor": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" } ], "thesis_committee": [ { "family_name": "Kuppermann", "given_name": "Aron", "clpid": "Kuppermann-A" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A recursion relation is formulated for the Green's function for calculating the effective electron coupling in bridge-assisted electron transfer systems, within the framework of the tight-binding Hamiltonian. The non-perturbative recursion expression relates the Green\u2019s function of a chain bridge to that of a bridge which is one unit less. The method is used to calculate the electronic coupling between a gold electrode and each of the molecules. (\u03b7\u2075-C\u2085H\u2085)Fe(\u03b7\u2075-C\u2085H\u2084)CO\u2082(CH\u2082)\u2099SH and (\u03b7\u2075-C\u2085H\u2085)Fe(\u03b7\u2075-C\u2085H\u2084)(CH\u2082)\u2099SH (n = 3 to 50). At larger numbers of bridge units, the effective coupling strength shows an exponential decay as the number of methylene units increases. This sequential formalism shows numerical stability even for a very long chain bridge and. since it uses only small matrices, requires much less computer time for the calculation. Identical bridge units are not a requirement, and so the method can be applied to more complicated systems, such as proteins. Most of the calculated coupling strengths, if converted to rate constants according to a nonadiabatic expression, agree well with the experimental results.
\r\n\r\nThe time-dependent dynamic Stokes shift function, which describes the solvent response to a sudden change in the charge distribution of a solute molecule, is expressed in terms of experimentally measured dielectric dispersion data of the solvent, using a simple dielectric continuum model. The result is applied to photoexcited coumarin 343 in water, and encouraging agreement with the experimental data is obtained. A simple formula is also derived which includes the effect of a pump pulse of finite duration. Such an effect is negligible when the frequency of a pump pulse is close to the maximum in the absorption spectrum, but a deviation from the standard formula can be expected for the pump pulse tuned to a far wing of the absorption band of the chromophore. To calculate further the time-dependent fluorescence spectral lineshapes, a method is described for incorporating the vibronic transitions of a solute molecule. The intramolecular vibrational relaxation is assumed to be much faster\r\nthan the observation delay time. Calculations are made for coumarin 153 in acetonitrile. The results are again in encouraging agreement with experimental spectra. Results are also given for the dynamic Stokes shift in methanol.
", "doi": "10.7907/k5yt-g844", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:17543", "collection": "thesis", "collection_id": "17543", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07212025-032307531", "primary_object_url": { "basename": "Kenyon_CN_1997.pdf", "content": "final", "filesize": 58673989, "license": "other", "mime_type": "application/pdf", "url": "/17543/1/Kenyon_CN_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Time-Resolved and Steady-State Investigations of Carrier Dynamics at the Semiconductor/Liquid Interface", "author": [ { "family_name": "Kenyon", "given_name": "Christopher Neil", "clpid": "Kenyon-Christopher-Neil" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Barton", "given_name": "Jacqueline K.", "orcid": "0000-0001-9883-1600", "clpid": "Barton-J-K" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Fundamental investigations of carrier transport and charge transfer at the\r\nsemiconductor/liquid interface are presented. The application of both steady-state and time-resolved\r\nmethods to these studies is discussed.
\r\n\r\nSmall signal photocurrent transients have been measured for n-Si/CH3OH-dimethylferrocene\r\n(Me2Fc)+/0/Pt and n-Si/Au/CH3OH-Me2Fc+/0/Pt interfaces. The\r\nphotocurrent transients for these interfaces decayed in less than 10 \u03bcs, and were limited by the\r\nseries resistance of the cell in combination with the space charge capacitance of the\r\nsemiconductor. An equivalent circuit model is presented and physically justified in order to\r\nexplain this behavior, and to elucidate the conditions under which photocurrent transients at\r\nsemiconductor electrodes can be expected to yield information regarding the faradaic charge\r\ntransfer rate across the semiconductor/liquid interface. To provide additional support for\r\nthe equivalent circuit representation, transient photocurrent responses are also presented for\r\nn-Si/Pt/NaOH(aq)/Ni(OH)2//Ni, n-TiO2//NaOH(aq)/Ni(OH)2//Ni and n-TiO2//NaOH(aq)Fe(CN)63-/4-fNi(OH)2/Ni contacts.
\r\n\r\nStudies are reported on the behaviors of thin, nearly intrinsically doped Si\r\nelectrodes having interdigitated n+ and p+ back contact points. An analysis of the factors\r\ngoverning the photocurrent directionality and photovoltage in these samples is presented.\r\nAdditionally the back contact geometry has been exploited to perform measurements of the\r\nopen circuit potential of either electrons or holes while the other carrier type was under\r\nelectrical control. In combination with current density-voltage measurements of carriers\r\npassing through the back contact points, these data allowed a comparison of the behavior of\r\na given carrier type when generated by an applied bias (i.e., as majority carriers) relative to\r\ntheir behavior when generated with band gap illumination of the solid (as minority\r\ncarriers). The results have been used to validate certain key predictions of the quasi-Fermi\r\nlevel concept in photo-electrochemistry. In addition, digital simulations that include two-dimensional\r\nrepresentations of the charge density distribution and of the current fluxes in\r\nthe solid have been utilized to provide a quantitative understanding of the observed\r\nexperimental behavior.
\r\n\r\nThe application of time-resolved photoluminescence to the study of InP interfaces is\r\ndescribed. Photoluminescence decay profiles for etched n-type and p-type InP have been\r\nrecorded. These data provide support for a bulk-recombination limited PL lifetime in p-InP,\r\nwhile that of n-InP is evidenced to be dominated by radiative recombination.\r\nAdditional PL decay data are reported for a series of InP/liquid contacts. InP/CH3CN\r\njunctions having Me2Fc+/0, decamethylferrocene+/0 (Me10Fc+/0), methyl viologen\r\n(MV)2+/+, and cobaltocene (COCp2)+/0 as acceptor species have been studied. Quantitative\r\ninformation on the rate constant for charge transfer could not be obtained from these\r\nstudies, but upper limits are suggested, and promising systems for further study are\r\nidentified.
", "doi": "10.7907/ef6e-0w18", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:17532", "collection": "thesis", "collection_id": "17532", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07162025-164213008", "primary_object_url": { "basename": "Bansal_A_1997.pdf", "content": "final", "filesize": 61905298, "license": "other", "mime_type": "application/pdf", "url": "/17532/1/Bansal_A_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Surface Modification and Charge Transfer Studies at Silicon and Gallium Arsenide Interfaces", "author": [ { "family_name": "Bansal", "given_name": "Ashish", "clpid": "Bansal-Ashish" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The thesis describes some chemical modifications of Si and GaAs surfaces, as a\r\nmeans of gaining control over the physical, chemical and electrical properties of these\r\nsurface and of the interfaces formed from these surfaces.
\r\n\r\nThe Current-voltage properties of n-GaAs photoanodes were evaluated in\r\nKOH-Se/2-(aq), CH3CN-ferrocene (Fc)+/0, and CH3CN-methyl viologen (MV)2+/+\r\nsolutions. Chemisorption of transition-metal ions (RhIII, RhIII, CoIII, OsIII) onto GaAs has\r\nbeen shown previously to effect improved photoanode behavior for n-GaAs/KOH-Se/2-\r\n(aq) contacts, but it is not clear whether the chemisorbed metal forms a buried\r\nsemiconductor/metal (Schottky) junction or results in a \"hybrid\" semiconductor/metal/liquid\r\ncontact. Metal ion treated n-GaAs photoanodes displayed different open circuit voltages in\r\ncontact with each electrolyte solution investigated. The role of the chemisorbed metal in the\r\nn-GaAs/KOH-Se/2-(aq) system is, therefore, best described as catalyzing interfacial charge\r\ntransfer at the semiconductor/liquid interface, as opposed to forming a semiconductor/metal\r\nor semiconductor/insulator/metal contact.
\r\n\r\nThe ability to modify Si surf ace without partial oxidation or formation of electrical\r\ndefects is potentially important. However, little is known about the chemistry of these\r\nsurfaces under ambient temperature and pressure. A two-step halogenation/alkylation route\r\nto chemical functionalization of Si(111) surf ace is described, that allows covalent\r\nattachment of alkyl functionalities without concomitant oxidation of the silicon surface. In\r\nthe first step, a hydrogen terminated silicon surface is chlorinated to obtain a chlorine\r\nterminated silicon surface. In the second step, the chlorinated surface is reacted with alkyl\r\nlithium or alkyl Grignard to obtain an alkyl terminated surface. The surface of silicon is\r\nextensively analyzed using a number of techniques such as XPS, HREELS, IRS, AES,\r\nTPD etc. The alkyl terminated surfaces are more resistant to oxidation in air and in contact\r\nwith wet chemical environments than the H-terminated surface.
\r\n\r\nCurrent-voltage and capacitance-voltage measurements of the alkyl terminated\r\nsurfaces in CH3OH-Me2Fc+/0 indicate that the electrical properties of these surfaces are\r\nvery similar to those of a H-terminated surface. The alkyl overlayers provide a small\r\nresistance to charge transfer across the Si/liquid interface but do not shift the band edges or\r\ninduce additional surface recombination. I-V characteristics of n-Si/alkyl/Au MIS devices\r\nindicate that these junctions behave largely liken-Si/Au Schottky junctions. The efficacy of\r\nalkyl overlayers in preventing photooxidation and photocorrosion of n-silicon surfaces was\r\nmeasured in contact with Fe(CN)63-/4-(aq) and with CH3OH-Me2Fc+/0 containing known\r\namounts of water. The alkyl terminated surfaces consistently show better I-V\r\ncharacteristics and lower oxidation than the H-terminated surface, indicating that stability to\r\noxidation had been achieved without any significant compromise in the electrical quality of\r\nthe silicon surface.
", "doi": "10.7907/5k6w-kt74", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:17525", "collection": "thesis", "collection_id": "17525", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07142025-223721756", "primary_object_url": { "basename": "Kesselman_JM_1997.pdf", "content": "final", "filesize": 48945859, "license": "other", "mime_type": "application/pdf", "url": "/17525/1/Kesselman_JM_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Fundamental Photoelectrochemical Properties of TIO\u2082/Water Interfaces : Relevance for Hazardous Waste Remediation", "author": [ { "family_name": "Kesselman", "given_name": "Janet M.", "clpid": "Kesselman-Janet-M" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Davis", "given_name": "Mark E.", "orcid": "0000-0001-8294-1477", "clpid": "Davis-M-E" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "TiO\u2082 photocatalysis is a promising technology for the treatment of aqueous or\r\ngaseous systems contaminated by low levels of organic pollutants. The research\r\ndescribed in this thesis explores fundamental mechanistic and kinetic questions for both\r\nTiO\u2082 photocatalytic and electrocatalytic degradation of aqueous organic contaminants. A\r\nrecurring theme in this thesis is the use of TiO\u2082 electrodes to investigate kinetic and\r\nmechanistic aspects of the TiO\u2082 photocatalytic process. The use of electrodes provides\r\nadditional experimental control of system parameters that is not possible in conventional\r\nTiO\u2082 slurry reactors.
\r\n\r\nThe first study reports the kinetics of oxygen reduction at single-crystal, rutile\r\nTiO\u2082 electrodes as a function of applied potential. Platinum deposits are found to\r\ncatalyze the reduction of oxygen at this surface. Application of a flux-matching condition\r\nto the independently measured reduction and photooxidation currents predicts significant\r\nrecombination losses for TiO\u2082 particles operating under steady-state photocatalytic\r\nconditions.
\r\n\r\nIn a second project, the contributions of direct and hydroxyl radical mediated\r\noxidation pathways are determined at Nb-doped, polycrystalline TiO\u2082 electrodes. In addition to quantifying the branching ratio of these two mechanisms for a variety of\r\norganic substrates, the results suggest that surface interactions are important in\r\ndetermining the predominant reaction pathway in these systems.
\r\n\r\nFinally, the adsorption of 4-chlorocatechol at the TiO\u2082/H\u2082O interface is\r\ninvestigated as a function of pH and solution concentration. Quantitative measurements\r\nof the extent of adsorption are reported as well as spectroscopic evidence for the structure\r\nof the adsorbed complex. Further work correlates observed photocatalytic degradation\r\nrates with the extent of adsorption under various solution conditions.
", "doi": "10.7907/5dmz-sa21", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:14502", "collection": "thesis", "collection_id": "14502", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02172022-225929135", "primary_object_url": { "basename": "Quantum_effects_in_electron_tr.pdf", "content": "final", "filesize": 4039615, "license": "other", "mime_type": "application/pdf", "url": "/14502/1/Quantum_effects_in_electron_tr.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Quantum Effects in Electron Transfer Reactions and Solvation Dynamics", "author": [ { "family_name": "Song", "given_name": "Xueyu", "orcid": "0000-0001-5142-4223", "clpid": "Song-Xueyu" } ], "thesis_advisor": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" } ], "thesis_committee": [ { "family_name": "Kuppermann", "given_name": "Aron", "clpid": "Kuppermann-A" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis focuses on the quantum effects of electron transfer reactions in solutions and solvation dynamics of pure solvent. A prototypical model system, the\r\nFe\u207a\u00b2 + Fe\u207a\u00b3 \u21cc Fe\u207a\u00b3 + Fe\u207a\u00b2 reaction in water, is treated using the spin-boson Hamiltonian model. The spectral density is related to the experimentally accessible data\r\non the dielectric dispersion of the solvent, using a dielectric continuum approximation. On this basis the quantum correction for the ferrous-ferric electron transfer rate is found to be a factor of 9.6, which is significantly smaller than the corresponding values calculated from molecular models which neglect the electronic and vibrational polarization of the solvent. Using an imaginary free energy method, a general formula for the rate valid in all orders of perturbation in electronic coupling is derived for a renormalized classical bath. It is found that the quantum degrees of freedom can be effectively eliminated from the model by renormalizing the electronic coupling matrix element to the first order approximation for the quantum modes. Furthermore, a similar result is obtained for the quantum bath with a better approximation scheme. In application it has been shown that the rate has a nonmonotonic behavior as a function of the coupling matrix element in the inverted region. In the solvent dynamics controlled regime a one-particle Green function method is used to calculate the electron transfer reaction rate with a spin-boson Hamiltonian. A quantum version of Zusman\u2019s result on solvent dynamical effect in electron transfer reactions is obtained for the symmetric case. It is shown that the quantum effect for most of the realistic systems is not significant at room temperature and it would become important for some fast dielectric relaxation solvents like water. In solvation dynamics studies a Gaussian field model is used to obtain the charge density correlation function of the solution in terms of charge density correlation function of the solvent. It then becomes possible to calculate the time-dependent solvation free energy without using the \"uniform dielectric approximation.\" It is found that the nonuniformity in the vicinity of the solute indeed retards the solvation relaxation.", "doi": "10.7907/ejw2-cy95", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:11894", "collection": "thesis", "collection_id": "11894", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11052019-113518368", "primary_object_url": { "basename": "Blake_RE_1996.pdf", "content": "final", "filesize": 43955318, "license": "other", "mime_type": "application/pdf", "url": "/11894/1/Blake_RE_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Synthesis, Characterization and Study of Transition Metal Complexes for the Oxidation and Activation of Hydrocarbons", "author": [ { "family_name": "Blake", "given_name": "Robert Edward, Jr.", "clpid": "Blake-Robert-Edward-Jr" } ], "thesis_advisor": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Goddard", "given_name": "William A., III", "clpid": "Goddard-W-A-III" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The reaction of previously characterized ruthenium oxo complex, [LOEtRuV(O)(\u00b5-O)]2 with alcohol substrates was undertaken to elucidate the mechanism of the oxidation reaction. Unfortunately, an autocatalytic reaction between the organometallic product, [LOEtRuIV(OH)(\u00b5-O)]2 and the reactant alcohol, as well as catalyst decomposition made exact determinations of rate constants impossible. During the course of this investigation, the free acid form of the ligand, LOEtH, was isolated as a viscous oil. Subsequent investigation of the reactions of [LOEtRuV(O)(\u00b5-O)]2 with other species such as acids, salts and bases demonstrated the inherent instability of the complex. In several cases, initial products were spectroscopically characterized, but isolation of pure compounds was not achieved.
\r\n\r\nGiven the problems with the decomposition of ruthenium complexes which utilized the Klaui ligand, trimetaphosphate was studied as a potentially oxidation-resistant alternative for the development of oxidation catalysts. Attempts were made to prepare salts of the trimetaphosphate ligand which are soluble in nonpolar media and free of water of hydration. Coordination complexes of the trimetaphosphate anion and transition elements were synthesized. The mode of coordination and stability of the ligand was examined by infrared and visible spectroscopy. In all cases, the very weakly coordinating trimetaphosphate anion failed to displace other weakly associated ligands from the metal, failed to adopt the proper coordination geometry or was easily removed from the metal center by water.
\r\n\r\nHexabenzyloxycyclotriphosphatriene was synthesized and thermally rearranged to 1,3,5 - tribenzyl - 2,4,6 tribenzyloxy - 2,4,6 trioxocyclotriphosphazane as per published procedures. Characterization of the rearranged product by NMR techniques revealed the previously undetermined stereochemistry of the product. This ligand precursor has been shown to react with trialkyl silyl chlorides, although the products have not been characterized.
\r\n\r\nCp*2Ta(=NtBu)(THF)[B(C6F5)4] (1) was synthesized according to the method developed previously in our group. A cationic analog to Bergman's Cp2Zr(=NtBu), the reactivity of this complex to hydrocarbon substrates was studied. Contrary to previous reports, this complex does not react with methane, but C-H activation reactions were observed for propyne and phenyl acetylene. In the propyne case, an initial mixture of the [2+2] and C-H activation products was driven to exclusively the C-H activation product thermally. An interesting intramolecular activation of a Cp* methyl group precludes much of the desired C-H activation chemistry. The steric demands of the active site was demonstrated by the observed reaction with ethylene, but the lack of reactivity towards propene. A very interesting dealkylation of the imido group was observed upon reaction with carbon dioxide, which is proposed to involve the intermediacy of a coordinated isocyanate. Cp*2Ta(=NtBu)(THF)[B(C6F5)4] reacts as expected with water, HCl and dihydrogen, and reacts cleanly with methylene chloride to give Cp*2Ta(NHtBu)Cl[B(C6F5)4]. Many of the new compounds have been crystallographically and spectroscopically characterized. The reactivity of this complex can be rationalized in terms of the presence of both electrophilic and nucleophilic sites in the same molecule.
", "doi": "10.7907/s731-np77", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:7712", "collection": "thesis", "collection_id": "7712", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05152013-113928711", "type": "thesis", "title": "The Design and Synthesis of a True, Heterogeneous, Asymmetric Catalyst", "author": [ { "family_name": "Wan", "given_name": "Kam To", "clpid": "Wan-Kam-To" } ], "thesis_advisor": [ { "family_name": "Davis", "given_name": "Mark E.", "clpid": "Davis-M-E" } ], "thesis_committee": [ { "family_name": "Davis", "given_name": "Mark E.", "clpid": "Davis-M-E" }, { "family_name": "Gray", "given_name": "Harry B.", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "McKoy", "given_name": "Basil Vincent", "clpid": "McKoy-B-V" }, { "family_name": "Labinger", "given_name": "Jay A.", "clpid": "Labinger-J-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This work describes the design and synthesis of a true, heterogeneous,\r\nasymmetric catalyst. The catalyst consists of a thin film that resides on a high-surface-\r\narea hydrophilic solid and is composed of a chiral, hydrophilic\r\norganometallic complex dissolved in ethylene glycol. Reactions of prochiral\r\norganic reactants take place predominantly at the ethylene glycol-bulk organic\r\ninterface.
\r\n\r\nThe synthesis of this new heterogeneous catalyst is accomplished in a\r\nseries of designed steps. A novel, water-soluble, tetrasulfonated 2,2'-bis\r\n(diphenylphosphino)-1,1'-binaphthyl (BINAP-4S0_3Na) is synthesized by\r\ndirect sulfonation of 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP).\r\nThe rhodium (I) complex of BINAP-4SO_3Na is prepared and is shown to be\r\nthe first homogeneous catalyst to perform asymmetric reductions of prochiral\r\n2-acetamidoacrylic acids in neat water with enantioselectivities as high as\r\nthose obtained in non-aqueous solvents. The ruthenium (II) complex,\r\n[Ru(BINAP-4SO_3Na)(benzene)Cl]Cl is also synthesized and exhibits a broader\r\nsubstrate specificity as well as higher enantioselectivities for the homogeneous\r\nasymmetric reduction of prochiral 2-acylamino acid precursors in water.\r\nAquation of the ruthenium-chloro bond in water is found to be detrimental to\r\nthe enantioselectivity with some substrates. Replacement of water by ethylene\r\nglycol results in the same high e.e's as those found in neat methanol. The\r\nruthenium complex is impregnated onto a controlled pore-size glass CPG-240 by the incipient wetness technique. Anhydrous ethylene glycol is used as the\r\nimmobilizing agent in this heterogeneous catalyst, and a non-polar 1:1\r\nmixture of chloroform and cyclohexane is employed as the organic phase.
\r\n\r\nAsymmetric reduction of 2-(6'-methoxy-2'-naphthyl)acrylic acid to the\r\nnon-steroidal anti-inflammatory agent, naproxen, is accomplished with this\r\nheterogeneous catalyst at a third of the rate observed in homogeneous\r\nsolution with an e.e. of 96% at a reaction temperature of 3\u00b0C and 1,400 psig of\r\nhydrogen. No leaching of the ruthenium complex into the bulk organic phase\r\nis found at a detection limit of 32 ppb. Recycling of the catalyst is possible\r\nwithout any loss in enantioselectivity. Long-term stability of this new\r\nheterogeneous catalyst is proven by a self-assembly test. That is, under the\r\nreaction conditions, the individual components of the present catalytic system\r\nself-assemble into the supported-catalyst configuration.
\r\n\r\nThe strategies outlined here for the design and synthesis of this new\r\nheterogeneous catalyst are general, and can hopefully be applied to the\r\ndevelopment of other heterogeneous, asymmetric catalysts.
\r\n", "doi": "10.7907/6m3g-3y70", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:5355", "collection": "thesis", "collection_id": "5355", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11052009-142520920", "type": "thesis", "title": "Electronic Structure and Photochemical Reactivity of Binuclear Metal Complexes", "author": [ { "family_name": "Smith", "given_name": "David Charles", "clpid": "Smith-David-Charles" } ], "thesis_advisor": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A valence bond (VB) \"weak coupling\" model of the electronic structure for [Ir\u2082(TMB)\u2084](B(C\u2086H\u2085)\u2084)\u2082 is developed and generalized to the class of dimeric systems in which the metals are nonbonded, in a formal sense, and can be viewed as weakly coupled. With the VB model, the energies and widths of the previously observed optical absorption bands can be rationalized; in addition, plausible assignments are made for bands that were not interpreted satisfactorily or not observed in earlier work. The VB model does not change any of the molecular orbital-based interpretations of the thermal chemistry, photochemistry, or photophysics of these systems.
\r\n\r\nPhotophysical characterization of the 1,3(d\u03c3*p\u03c3) excited state of Ir\u2082(TMB)\u2084\u00b2\u207a finds a system quite comparable to other binuclear d\u2078 complexes. Both fluorescence (\u03bb\u2098\u2090\u2093 735 nm, \u03c4 ~ 70 \u00b1 30 ps) and phosphorescence (\u03bb\u2098\u2090\u2093 1080 nm, \u03c4 = 210 \u00b1 20 ns) are observed.
\r\n\r\nThe relatively long lifetime of the \u00b3(d\u03c3*p\u03c3) excited state of Ir\u2082(TMB)\u2084\u00b2\u207a suggests that it should be able to participate in bimolecular photochemical reactions. The diradical-like structure of the excited state, an electron (or oxidizing hole) localized on the exterior of the M\u2082 unit (the d\u03c3* orbital) and an electron localized in the interior of the dimer cage (the p\u03c3 orbital), implies that one-electron chemistry will be observed. Reactions of the ground state follow two-electron pathways, similar to those observed for mononuclear d\u2078 complexes.
\r\n\r\nThe \u00b3(d\u03c3*p\u03c3) excited state of Ir\u2082(TMB)\u2084\u00b2\u207a is found to be a powerful reductant, E\u2070(Ir\u2082(TMB)\u20843+/3(Ir\u2082(TMB)\u2084\u00b2\u207a)*) ~ 1.0 V (SSCE). Excited-state electron- transfer quenching by pyridinium acceptors is observed to follow classical Marcus theory for outer-sphere electron transfer. No \"inverted\" behavior is found. The bimolecular electron-transfer reaction is highly nonadiabatic, \u03ba ~ 0.0001, because of the large donor-acceptor separation, ~ 8 \u00c5. The results for Ir\u2082(TMB)\u2084\u00b2\u207a are discussed in comparison to those for [Ir(\u00b5-pz)COD]\u2082.
\r\n\r\nIr\u2082(TMB)\u2084\u00b2\u207a is found to react photochemically with alkyl halides. Although the \u00b3(d\u03c3*p\u03c3) excited state is a good reductant, outer-sphere electron transfer seems unlikely (E\u2070(RX/RX\u2022-) < -1.5 V (SSCE)). An SRN1 pathway has been suggested to explain the alkyl halide photoreduction reaction observed for metal complexes with E\u2070(M\u2082+/3M\u2082*) < -1.5 V (SSCE); however, atom transfer to the \u00b3(d\u03c3*p\u03c3) excited state is the favored reaction mechanism for the alkyl halide photoreduction reaction of Ir\u2082(TMB)\u2084\u00b2\u207a. The generality of this reaction is discussed.
\r\n\r\nWhile there is some ambiguity as to the primary photoprocess for alkyl halide photoreactivity, \u00b3(d\u03c3*p\u03c3) excited-state hydrogen-atom transfer has been established as the mechanism of the reaction of Ir\u2082(TMB)\u2084\u00b2\u207a and a number of organic substrates. The atom-transfer reactivity of the \u00b3(d\u03c3*p\u03c3) excited state is attributed to the presence of a hole in the d\u03c3* orbital, analogous to the \u00b3n\u03c0* state of organic ketones. Interaction of the oxidizing hole with the electron pair of the C-H bond is the presumed pathway.
\r\n\r\nElectrochemical oxidation of Rh\u2082(TMB)\u2084\u00b2\u207a generates the d\u2078-d\u2077 species Rh\u2082(TMB)\u2084\u00b3\u207a. This complex reacts with 1,4-cyclohexadiene to abstract a hydrogen atom mimicking the initial step of the \u00b3(d\u03c3*p\u03c3) photoreaction. The importance of this result is discussed in terms of energy storage systems and extension of the range of hydrocarbon oxidations with binuclear d\u2078 complexes.
\r\n\r\nThe d\u2077-d\u2077 dihydride product obtained from the photoreaction of Ir\u2082(TMB)\u2084\u00b2\u207a and 1,4-cyclohexadiene is isolated and characterized. In addition to NMR, UV-Vis, IR, and Raman spectra, the complex is characterized crystallographically. The reactivity of this complex is also discussed.
", "doi": "10.7907/q1gz-dn84", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:1862", "collection": "thesis", "collection_id": "1862", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05182007-110357", "type": "thesis", "title": "Synthesis and Characterization of Quantum Size Metal Oxide Colloidal Particles. Photocatalytic Peroxide Formation on ZnO and TiO\u2082", "author": [ { "family_name": "Kormann", "given_name": "Claudius", "clpid": "Kormann-Claudius" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Weinberg", "given_name": "William Henry", "clpid": "Weinberg-W-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The syntheses of transparent colloidal solutions of extremely small ZnO (d < 5nm) and TiO\u2082 (d < 3 nm) particles in water, alcohol, and acetonitrile are presented. Quantum size effects are observed during particle growth and at final stages of synthesis. They are qualitatively and quantitatively (TiO\u2082) interpreted by using a simple molecular orbital (MO) picture and a quantum mechanical model developed by Brus. The optical absorption and fluorescence properties as well as the surface acid-base properties are characterized in detail. The two materials are shown to be active photocatalysts in the formation and degradation of H\u2082O\u2082 and organic peroxides and in the degradation of chlorinated hydrocarbons. Quantum yields and steady state concentrations are given as function of various reaction parameters such as the oxygen concentration, the nature and concentration of electron donor, pH, and charge of the electron donor. Rates of reaction are correlated with surface speciation as calculated by the SURFEQL computer code. Transparent colloidal solutions of Fe\u2082O\u2083 (hematite) have also been prepared, however only negligible photocatalytic activity is found when compared to ZnO and TiO\u2082. Evidence is presented for OH\u2022 radical activity when aqueous TiO\u2082 suspensions are illuminated at high pH.
", "doi": "10.7907/bya7-6g55", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:7849", "collection": "thesis", "collection_id": "7849", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062013-085651174", "type": "thesis", "title": "Reactivity of Titanocene Methylidene with Metal Halides, Alkene Sulfides, and Alkene Oxides", "author": [ { "family_name": "Park", "given_name": "Joon Won", "clpid": "Park-Joon-Won" } ], "thesis_advisor": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "thesis_committee": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Myers", "given_name": "Andrew G.", "clpid": "Myers-A-G" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Titanocene metallacyclobutanes show a wide variety of reactivites with organic and inorganic reagents. Their reactions include methylene transfer to organic carbonyls, formation of enolates, electron transfer from activated alkyl chlorides, olefin metathesis, ring opening polymerization. Recently, preparations of heterobinuclear \u00b5-methylene complexes were reported. In this thesis, mechanistic, synthetic, and structural studies of the heterobinuclear \u00b5-methylene complexes will be described. Also, the reaction of titanocene methylidene trimethylphosphine complex with alkene sulfide and styrene sulfide will be presented.
\r\n\r\nHeterobinuclear \u00b5-methylene-\u00b5-methyl complexes Cp\u2082Ti(\u00b5-CH\u2082)(\u00b5-CH\u2083)M(1,5-COD) have been prepared (M = Rh, Ir). X-ray crystallography showed that the methyl group of the complex was bonded to the rhodium and bridges to the titanium through an agostic bond. The \u00b9H, \u00b9\u00b3CNMR, IR spectra along with partial deuteration studies supported the structure in both solution and solid state. Activation of the agostic bond is demonstrated by the equilibration of the \u00b5-CH\u2083 and \u00b5-CH\u2082 groups. A nonlinear Arrhenius plot, an unusually large kinetic isotope effect (24(5)), and a large negative activation entropy (-64(3)eu) can be explained by the quantum-mechanical tunneling. Calculated rate constants with Bell-type barrier fitted well with the observed one. This equilibration was best explained by a 4e-4c mechanism (or \u03c3 bond metathesis) with the character of quantum-mechanical tunneling.
\r\n\r\nHeterobinuclear \u00b5-methylene-\u00b5-phenyl complexes were synthesized. Structural study of Cp\u2082Ti(\u00b5-CH\u2082)(\u00b5-p-Me\u2082NC\u2086H\u2084)Rh(l,5-COD) showed that the two metal atoms are bridged by the methylene carbon and the ipso carbon of the p-N,N-dimethylarninophenyl group. The analogous structure of Cp\u2082Ti(\u00b5-CHp\u2082)(\u00b5-o-MeOC\u2086H\u2084)Rh(1,5-COD) has been verified by the differential NOE. The aromaticity of the phenyl group observed by \u00b9H NMR, was confirmed by the comparison of the C-C bond lengths in the crystallographic structure. The unusual downfield shifts of the ipso carbon in the \u00b9\u00b3C NMR are assumed to be an indication of the interaction between the ipso carbon and electron-deficient titanium.
\r\n\r\nTitanium-platinum heterobinuclear \u00b5-methylene complexes Cp\u2082Ti(\u00b5-CH\u2082)(\u00b5-X)Pt(Me)(PMe\u2082Ph) have been prepared (X = Cl, Me). Structural studies indicate the following:(1) the Ti-CH\u2082 bond possesses residual double bond character, (2) there is a dative Pt \u2192 Ti interaction which may be regarded as a \u03c0 back donation from the platinum atom to the \"Ti=CH\u2082\" group, and (3) the \u00b5-CH\u2083 group is bound to the titanium atom through a three-center, two-electron agostic bond.
\r\n\r\nTitanocene (\u03b7\u00b2-thioformaldehyde)\u2022PMe\u2083 was prepared from Cp\u2082Ti=CH\u2082\u2022PMe\u2083 and sulfur-containing organic compounds (e.g. alkene sulfide, triphenylphosphine sulfide) including elemental sulfur. Mechanistic studies utilizing trans-styrene sulfide-d\u2081 suggested the stepwise reaction to explain equimolar mixture of trans- and cis-styrene-d\u2081 as by-products. The product reacted with methyl iodide to produce cationic titanocene (\u03b7\u00b2-thiomethoxymethyl) complex. Complexes having less coordinating anion like BF\u2084 or BPh\u2084 could be obtained through metathesis. Together with structural analyses, the further reactivities of the complexes have been explored.
\r\n\r\nThe complex [chemical formula; see thesis file (PDF) abstract for details] was prepared from the compound Cp\u2082Ti=CH\u2082-PMe\u2083 and styrene oxide. The product was characterized with \u00b9H-\u00b9H correlated 2-dimensional NMR, selective decoupling of \u00b9H NMR, and differential NOE. Stereospecificity of deuterium in the product was lost when trans-styrene oxide-d\u2081 was allowed to react. Relative rates of the reaction were measured with varying substituents on the phenyl ring. Better linearity (r = -0.98, \u03c1\u207a = -0.79) was observed with \u03c3p\u207a than \u03c3(r = -0.87, \u03c1 = -1.26). The small magnitude of \u03c1\u207a value and stereospecificity loss during the formation of product were best explained by the generation of biradicals, but partial generation of charge cannot be excluded. Carbonylation of the product followed by exposure to iodine yields the corresponding \u03b2-phenyl \u03b3-lactone.
", "doi": "10.7907/0ds2-5h68", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:9057", "collection": "thesis", "collection_id": "9057", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07102015-095638444", "primary_object_url": { "basename": "Ni_CL.pdf", "content": "final", "filesize": 25221116, "license": "other", "mime_type": "application/pdf", "url": "/9057/1/Ni_CL.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Electrocatalytic Reduction of Dioxygen at Chemically Modified Electrodes", "author": [ { "family_name": "Ni", "given_name": "Ching-Long", "clpid": "Ni-Ching-Long" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Chan", "given_name": "Sunney I.", "clpid": "Chan-S-I" }, { "family_name": "Schaefer", "given_name": "William P.", "clpid": "Schaefer-W-P" }, { "family_name": "Grubbs", "given_name": "Robert H.", "clpid": "Grubbs-R-H" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The kinetics of the reduction of O2 by Ru(NH3)6+2 as catalyzed by cobalt(II) tetrakis(4-N-methylpyridyl)porphyrin are described both in homogeneous solution and when the reactants are confined to Nafion coatings on graphite electrodes. The catalytic mechanism is determined and the factors that can control the total reduction currents at Nafion-coated electrodes are specified. A kinetic zone diagram for analyzing the behavior of catalyst-mediator-substrate systems at polymer coated electrodes is presented and utilized in identifying the current-limiting processes. Good agreement is demonstrated between calculated and measured reduction currents at rotating disk electrodes. The experimental conditions that will yield the optimum performance of coated electrodes are discussed, and a relationship is derived for the optimal coating thickness.
\r\n\r\nThe relation between the reduction potentials of adsorbed and unadsorbed cobalt(III) tetrakis(4-N-methylpyridyl)porphyrin and those where it catalyzes the electroreduction of dioxygen is described. There is an unusually large change in the formal potential of the Co(III) couple upon the adsorption of the porphyrin on the graphite electrode surface. The mechanism in which the (inevitably) adsorbed porphyrin catalyzes the reduction of O2 is in accord with a general mechanistic scheme proposed for most monomeric cobalt porphyrins.
\r\n\r\nFour new dimeric metalloporphyrins (prepared in the laboratory of Professor C. K. Chang) have the two porphyrin rings linked by an anthracene bridge attached to meso positions. The electrocatalytic behavior of the diporphyrins towards the reduction of O2 at graphite electrodes has been examined for the following combination of metal centers: Co-Cu, Co-Fe, Fe-Fe, Fe-H2. The Co-Cu diporphyrin catalyzes the reduction of O2 to H2O2 but no further. The other three catalysts all exhibit mixed reduction pathways leading to both H2O2 and H2O. However, the pathways that lead to H2O do not involve H2O2 as an intermediate. A possible mechanistic scheme is offered to account for the observed behavior.
", "doi": "10.7907/EPT0-NF02", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:11815", "collection": "thesis", "collection_id": "11815", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10112019-162918098", "type": "thesis", "title": "Electrochemical Studies Related to the Design of New Inorganic Oxidants", "author": [ { "family_name": "Gipson", "given_name": "Stephen Lloyd", "clpid": "Gipson-Stephen-Lloyd" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Collins", "given_name": "Terrence J.", "clpid": "Collins-T-J" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Schaefer", "given_name": "William P.", "clpid": "Schaefer-W-P" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The electrochemistry of complexes designed to address important questions in the field of oxidation chemistry has been examined. There is a need for new ligands capable of forming stable complexes with high oxidation state metal centers for the development of new oxidants with enhanced selectivity and reactivity for the oxidation of organic substrates. The electrochemistry of complexes of a family of potentially tetradentate tetraanionic ligands was examined to probe their reactivity, stability to oxidation and ability to stabilize high-valent metal centers.
\r\n\r\nAn osmium(IV) complex of the ligand 1,2-bis(3,5-dichloro-2-hydroxybenzamido) ethane (CHBA-Et) was found to undergo degradation of the ligand upon oxidation to Os(V) in CH2Cl2. In the presence of alcohols or water this oxidative degradation proceeded in a selective and stepwise fashion through a number of intermediate complexes which were isolated and characterized. The identification of the intermediates allowed a detailed mechanism for the degradation, accounting for both the products and their diastereomeric distribution, to be proposed. The final products of the oxidative degradation and subsequent hydrolysis reactions were found to contain bidentate dianionic 3,5-dichloro-2-hydroxybenzamido ligands (CHBA) and to be catalysts for the electrochemical oxidation of alcohols. These catalysts, and analogs prepared chemically, catalyzed the selective electrochemical oxidation of alchols to aldehydes and ketones, but had limited lifetimes. During the catalytic oxidation reactions the catalysts decomposed to unknown, inactive products. The maximum catalyst lifetime observed corresponded to the oxidation of approximately 150 moles of benzyl alcohol to benzaldehyde per mole of catalyst.
\r\n\r\nThe oxidative degradation of the CHBA-Et ligand was eliminated by replacement of the ethylene bridge with a dichlorobenzene bridge. Osmium (IV) complexes of the new ligand, 1,2-bis(3,5-dichloro-2-hydroxy-benzamido)-4,5-dichlorobenzene (CHBA-DCB) displayed reversible oxidations to Os(V) in CH2Cl2. Complexes of the non-chlorinated analog of this ligand, HBA-B, also displayed reversible oxidations to Os(V). There is some question about the oxidation state assignment in these complexes since oxidized forms of the ligands could contribute to the structure ofthe complexes and so reduce the formal oxidation state assignment of the metal. It is believed that at least the CHBA-DCB ligand forms true Os(V) complexes.
\r\n\r\nControlled potential oxidation of complexes such as Os(CHBA-DCB)(pyridine)2 led to partial isomerization from the trans to the cis-alpha isomer. This isomerization is believed to be triggered by the decrease in electron density at the metal center upon oxidation. Because of restriction of amide resonance in the nonplanar form of the ligand, it is a better electron donor in the cis-alpha isomer and so isomerization helps offset the loss of electron density caused by oxidation. A similar decrease in electron density and isomerization to the cis-alpha isomer is observed upon coordination of electron-withdrawing ligands to the Os(IV) complexes. Reduction of some of these cis-alpha Os(IV) complexes can cause isomerization to the more planar cis-beta isomer. An approximate correlation between the electron donating ability of the monodentate ligands and the equilibrium constant for the trans/cis-alpha isomerization at Os(V) was demonstrated. This observation indicates that the isomerization is primarily, but not exclusively, under electronic control.
\r\n\r\nBecause of the limited anodic range of the CH2Cl2 used as a solvent for the electrochemical studies of the CHBA-DCB complexes, no anodic activity past the Os(V/IV) couples could be observed. Therefore, the electrochemistry of some of these complexes was examined in liquid SO2 which has an anodic range to about +4 V vs. 8CE. The complexes displayed additional reversible oxidations in SO2, but these oxidations are believed to be ligand-localized. The complex Os(CHBA-Et)(pyridine)2 and its degradation products were also examined in SO2 and were found to display additional reversible oxidations not observable in CH2Cl2.
\r\n\r\nComplexes of the tetradentate tetraanionic ligands with cobalt(III) were also studied. These complexes could be oxidized to stable Co(IV) compounds. A second oxidation observed in acetonitrile and CH2Cl2 did not produce a stable Co(V) complex. In liquid SO2 the cobalt complexes displayed four reversible oxidations.
\r\n\r\nChemically modified electrodes were prepared from some of the complexes studied. The most stable electrodes were prepared by reductive electropolymerization of the complex K[Os(CHBA-Et)(4-vinylpyridine)2]. These electrodes showed stable electrochemical responses in acetonitrile, CH2Cl2 and aqueous media, but were not stable in nonaqueous acidic media or upon oxidation to Os(V). Because of the sensitivity to acid, these polymer modified electrodes could not be converted to the catalyst compounds.
", "doi": "10.7907/fyz2-qc15", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:17600", "collection": "thesis", "collection_id": "17600", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08062025-201831641", "primary_object_url": { "basename": "Ellis_WR_1986.pdf", "content": "final", "filesize": 46822265, "license": "other", "mime_type": "application/pdf", "url": "/17600/1/Ellis_WR_1986.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Spectroelectrochemical Studies of Heme and Copper Proteins", "author": [ { "family_name": "Ellis", "given_name": "Walther Robert, Jr.", "clpid": "Ellis-Walther-Robert" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Hopfield", "given_name": "John J.", "clpid": "Hopfield-J-J" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A complete characterization of the redox thermodynamics of a metalloprotein\r\ninvolves the determination of the effects of pH, ionic\r\nstrength, and temperature. In particular, variable-temperature reduction\r\npotential measurements yield the enthalpic and entropic contributions\r\nto EO, which, in turn, are related to kinetic activation\r\nparameters.
\r\n\r\nIn Chapter II of this thesis, the design of a versatile\r\nspectroelectrochemical apparatus for high precision measurements of\r\nmetalloprotein reduction potentials is described. A stainless steel\r\nshroud, necessary for anaerobic measurements, is used to house either\r\nof two types of spectroelectrochemical cells: a thin-layer optically\r\ntransparent electrode cell, or a two cm. stirred cell (useful for\r\nobserving weak chromophores). Both types of cells are suitable for\r\nvariable-temperature measurements using either absorption or circular\r\ndichroism spectroscopy. The latter offers a useful alternative to\r\nabsorption spectroscopy since redox mediators, which are almost always\r\nnecessary for electrochemical experiments on metalloproteins, are\r\ngenerally not optically active and therefore will not interfere with\r\nthe acquisition of protein circular dichroism spectra.
\r\n\r\nSpectroelectrochemical measurements for a selection of paradigmatic \r\nhemoproteins are presented in Chapter III. Horse heart\r\ncytochrome c is shown to yield redox thermodynamic parameters in excellent\r\nagreement with results of calorimetric determinations. Data\r\nfor R. palustris cytochrome c' and myoglobin are also presented\r\nand discussed with reference to extant spectroscopic and kinetic data, and\r\ncrystal structure determinations for these proteins. \u0394SO does not\r\ncorrelate with protein surface charge, unlike the well-known correlation\r\nof \u0394SO with charge for transition metal complexes. Instead, it\r\nis suggested that \u0394SO is (at least in part) determined by redox-linked\r\nprotein conformational changes. Next, redox thermodynamic parameters\r\nfor the azurins from A. denitrificans and A. faecalis are presented.\r\nThe azurin data show that proton uptake (in the region pKaox\r\nless than pH less than pKared) accompanying the reduction of the copper site decreases \u0394SO\r\nslightly. This observation is discussed in light of crystallographic\r\nstudies on \"blue\" copper proteins.
\r\n\r\nChapter IV discusses the problems of temperature and metal-metal\r\ninteractions associated with the equilibrium redox behavior of multisite\r\nmetalloproteins. An analogy between allosteric ligand binding\r\nand allosteric electron binding (i.e., reduction) is used to analyze\r\nNernst plots exhibiting unusual slopes. In interactive situations,\r\nthe conventionally defined reduction potential is not a simple\r\nthermodynamic quantity. This formalism is used in a discussion of the\r\nequilibrium redox interactions displayed by the optically visible\r\nmetal centers (CuA, Fe a, Fe a3) in cytochrome c oxidase. The commonly\r\naccepted \"neoclassical\" model, which only incorporates interaction\r\nbetween Fe a and Fe 3, is shown to be incorrect. The importance\r\nof temperature (leading to varying entropies of reduction for different\r\nmetal sites in a protein) is illustrated by a (NH3)5Ru(His-48)-derivative\r\nof sperm whale myoglobin. Kinetic and thermodynamic data\r\nfor this two-site protein lead to an estimate of 20 kcal/mol for the\r\nreorganizational enthalpy of the iron heme in myoglobin. This value\r\nsubstantially larger than the 7-8 kcal/mol estimate for horse\r\ncytochrome c, and is most likely due to a ligation change upon reduction\r\nof myoglobin wherein the axial water molecule dissociates from\r\nthe iron center.
\r\n\r\nA detailed discussion of the pH, ionic strength, and temperature\r\ndependences of the formal reduction potentials of the CuA, Fe a. and\r\nFe a3 centers in cytochrome oxidase is the topic of Chapter V. These\r\nresults are compared with values for other protein copper and heme\r\nsites and are discussed within the context of the known structural\r\nfeatures and reactivity of the enzyme.
", "doi": "10.7907/fqg8-e811", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:11350", "collection": "thesis", "collection_id": "11350", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01222019-123545387", "primary_object_url": { "basename": "Winniczek_JW_1985.pdf", "content": "final", "filesize": 110565437, "license": "other", "mime_type": "application/pdf", "url": "/11350/1/Winniczek_JW_1985.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Anisotropic Interaction Potentials between Helium and Linear Molecules from Crossed Beam Experiments", "author": [ { "family_name": "Winniczek", "given_name": "Jaroslaw W.", "clpid": "Winniczek-Jaroslaw-W" } ], "thesis_advisor": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Kuppermann", "given_name": "Aron", "clpid": "Kuppermann-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Janda", "given_name": "Kenneth C.", "clpid": "Janda-K-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Anisotropic interaction potentials between helium and linear molecules have been studied experimentally and theoretically to examine the relationship between the potential and the scattering differential cross-section, and to extract these potentials from crossed-molecular beam data.
\r\n\r\nChapter 2 presents the measurement of total (elastic and inelastic) differential scattering cross sections for He + CO2, CS2, OCS at a relative collision energy of about 65 meV with a crossed molecular beam apparatus. Anisotropic interaction potentials were extracted from these data, by way of an infinite order sudden approximation analysis. Several different anisotropic potential models were used in this analysis. The necessity for considering the anisotropy in the position of the well minimum as well as of its depth is demonstrated. A potential is proposed for He + OCS that reflects the symmetry of OCS, with a minimum number of modeling parameters.
\r\n\r\nIn Chapter 3 a detailed sensitivity analysis of the total and rotational state-to-state differential cross-section (DCS) is performed on an empirical potential energy surface for He + CO2. The infinite order sudden approximation is used to calculate the cross-sections. The sensitivity analysis consists of: 1) a large scale modification of the parameters that determine the anisotropic potential, and 2) an infinitesimal variation of these parameters to obtain a relative sensitivity function for the DCS. From these we demonstrate the effect each potential parameter has on the cross-sections. Despite the fact that this highly quantum system displays no classical effects such as rainbow scattering, we have shown that the quantal DCS oscillations contain significant information regarding the depth and width of the potential well and its anisotropy. Much of this information can be extracted from total-DCS scattering data. However the rotationally inelastic DCS contain a substantial amount of additional information regarding the shape of the potential energy surface.
\r\n\r\nSome of the conclusions reached in Chapter 3 indicate that the measuring of rotationally inelastic differential cross-sections can provide significantly greater insight into the nature of the potential than does the total DCS. In Chapter 4 we develop the means for simulating experimentally observable data from the potential for a given set of apparatus conditions. In Chapter 5 we describe modifications made to the crossed-beam apparatus in order to observe this inelasticity and present preliminary results for He + CO2.
", "doi": "10.7907/5nvw-ym37", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:11338", "collection": "thesis", "collection_id": "11338", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01112019-110100839", "primary_object_url": { "basename": "Tsou_Y-M_1985.pdf", "content": "final", "filesize": 39368691, "license": "other", "mime_type": "application/pdf", "url": "/11338/1/Tsou_Y-M_1985.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Thermodynamic and Kinetic Studies of Redox Reactions within Polyelectrolyte Coatings on Electrodes", "author": [ { "family_name": "Tsou", "given_name": "Yu-Min", "clpid": "Tsou-Yu-Min" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Collins", "given_name": "Terrence J.", "clpid": "Collins-T-J" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The formal potentials of several redox couples incorporated in coatings of a perfluorocarboxylate on graphite electrodes are measured and compared with the formal potentials of the same couples in homogeneous solution. For every redox couple investigated, the difference observed agrees with that calculated from the Nernst equation with the independently measured ratio of incorporation coefficients of the two halves of the couple. The dependences of the shifts in formal potentials on the nature of the incorporated complex ion, the ionic strength, and the temperature are also determined. They indicate that the incorporation equilibrium is governed by electrostatic and hydrophobic interactions that act in opposite directions. The incorporation of most cations examined is driven by large increases in entropy which overcome the usually unfavorable enthalpy changes.
\r\n\r\nThe mediated oxidation of ascorbate by Os(bpy)33+ incorporated in Nafion coatings on graphite electrodes is examined. Attempts to account for the magnitude of the mediated ascorbate oxidation currents in terms of current models and theories are only partially successful. As the ascorbate concentration is increased, the limiting oxidation currents at coated rotating disk electrodes do not increase as rapidly as expected on the basis of the models. Some possible reasons for this deviant behavior are suggested. The implications of the results on the general utility of Nafion-coated electrodes in electrocatalysis are presented.
\r\n\r\nThe heterobinuclear complex [formula; see abstract in scanned thesis for details] is synthesized and used as a probe to gain the insight into the diffusional behavior of redox reactants within polymeric coatings. Its diffusion coefficient within Nafion coatings is measured chronocoulometrically in all three of its possible redox states (RuIIILFeIII, RuIIILFeII, RuII LFeII). The three oxidation states exhibit large differences in their diffusional rates. Possible origins of the differences and their concentration dependences that are considered include intermolecular electron self- exchange, single- file diffusion and electrostatic cross-linking. Both enhancement and depression of charge transport rates produced by electron transfer cross-reactions between the fully oxidized and fully reduced complex are observed and compared with those calculated on the basis of a simple model. Reasonable agreement is obtained. The important effect that intermolecular cross-exchange reactions can exert on the diffusive flux of reactants is demonstrated.
", "doi": "10.7907/c31b-xm06", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1297", "collection": "thesis", "collection_id": "1297", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04072008-152253", "primary_object_url": { "basename": "Felker_pm_1985.pdf", "content": "final", "filesize": 8254391, "license": "other", "mime_type": "application/pdf", "url": "/1297/1/Felker_pm_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Picosecond Dynamics of Intramolecular Vibrational-Energy Redistribution (IVR) in Jet-Cooled Molecules", "author": [ { "family_name": "Felker", "given_name": "Peter Mark", "orcid": "0000-0002-4907-7231", "clpid": "Felker-Peter-Mark" } ], "thesis_advisor": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" } ], "thesis_committee": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" }, { "family_name": "McKoy", "given_name": "Basil Vincent", "clpid": "McKoy-B-V" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Theoretical and experimental results concerning the dynamical manifestations of intramolecular vibrational-energy redistribution (IVR) in the temporally resolved fluorescence of jet-cooled molecules are presented. A first concern is with the derivation of the characteristics of the beat-modulated fluorescence decays which arise from multilevel vibrational coupling within a molecule. Relations connecting quantum beat frequencies, phases, and modulation depths to coupling parameters are presented. Likely sources of deviations of experimental results from theoretical predictions are considered. And, the direct link between IVR and time-resolved fluorescence experiments is discussed with emphasis placed on the physical interpretation of vibrational quantum beats and the nature of IVR as a function of vibrational energy in a molecule. Secondly, the results of picosecond time-resolved measurements of IVR on jet-cooled anthracene at different excess energies are reported and analyzed. The nature of IVR as a function of vibrational energy, the relevant timescales for the process, and the details of pertinent vibrational couplings are determined. Thirdly, experimental and theoretical results pertaining to the role of molecular rotations in IVR are presented. Finally, experimental results on jet-cooled t-stilbene are reported and analyzed with the aim of assessing the generality of our theoretical treatment and the anthracene results.
", "doi": "10.7907/x48p-n096", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:11333", "collection": "thesis", "collection_id": "11333", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01042019-095546695", "type": "thesis", "title": "Photophysics and Electrochemistry of d\u2074 Metal Clusters", "author": [ { "family_name": "Zietlow", "given_name": "Thomas Christopher", "clpid": "Zietlow-Thomas-Christopher" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The metal-ligand and metal-metal interactions in d4 metal cluster systems have been examined using emission spectroscopy and electrochemical techniques. A detailed picture of the electronic structure of the hexanuclear molybdenum and tungsten clusters has not yet been achieved, but significant insight has been obtained through studying the effects of ligand, temperature, and molecular structure on the properties of the emissive excited state. Through these studies, and through analogy to the (d4)2 quadruply bonded molybdenum and tungsten dimers, the dynamics of the excited state, and its relevance to the chemistry out of that state, can be better understood.
\r\n\r\nThe work done on the excited state properties of the Mo6X2-14 (X = Cl, Br, I) clusters is outlined in Chapter 2. The energy of the emissive excited state is independent of halide ligand and is best described as a metallocalized state with very little ligand character. Energy transfer quenching data have determined that the emissive excited states are spin triplets.
\r\n\r\nThe unusual emissive behavior of the tungsten series W6X8Y2-6 (X, Y = Cl, Br, I) is discussed in Chapters 3 and 4. The energy of the emissive states order: W6Cl2-14 (1.83 eV) < W6Br2-14(1.85 eV) < W6I2-14(2.05 eV), the opposite trend from that expected by including charge transfer character into the transition. Variation of axial and facial halides leads to the conclusion that the \u00b53-bridging halides dominate the electronic structure of the cluster, but that the axial halides have a strong influence on the non-radiative rate. The structural studies show that the W-W bonds are longer in the W6I2-14 cluster than in the W6Cl2-14 structure, indicating that the metal-metal bond overlap is not the sole determining factor in the energy of the emitting excited states.
\r\n\r\nChapters 5, 6, and 7 describe the chemistry and properties of derivatives of these hexanuclear clusters. The W6Br-14 anion has been synthesized and its crystal structure determined. The effect of alkylphosphine ligands on the electrochemistry and photophysics of the Mo6Cl12 cluster has been found to be very small. Although the Mo5Xn-13 (n = 1, 2, 3) clusters do not appear to have any interesting photochemical properties, the observation of the splitting between spin-orbit states in a high nuclearity cluster has implications in the photochemistry of the hexanuclear clusters.
\r\n\r\nFinally, the last two chapters describe work done on the electrochemistry of Mo2X4 (PR3) 4 dimers. An unexpected ordering of the redox potentials is ascribed to \u03c0-backbonding from the metal center to the halide ligand. Efficient electrogenerated chemiluininescence has been observed for several of these dimers.
", "doi": "10.7907/x6gp-2861", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:11329", "collection": "thesis", "collection_id": "11329", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01022019-103725460", "type": "thesis", "title": "Synthesis and Characterization of a Ruthenium-EDTA Dimer by Spectral and Electrochemical Techniques", "author": [ { "family_name": "Baar", "given_name": "Roger Bennett", "clpid": "Baar-Roger-Bennett" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Section I
\r\n\r\nThe synthesis of a ruthenium-edta dimer is described. The dimer is shown to be the one-electron oxidized product of two [Ru(III)edta(OH2)]- monomers. The dimer was shown to contain one unpaired spin by magnetic susceptibility and esr spectroscopy indicating spin pairing between the two ruthenium metal centers. A band was detected in the near infrared that analyzed for a Class III complex indicating that the dimer is truly delocalized and that the oxidation state on each ruthenium is 3.5. The band was much narrower than predicted for a delocalized, Class II complex and its position did not exhibit any solvent dependence. The optical spectrum indicated some similarity with other formally Ru(III)-Ru(IV) dimers indicating that the formation of this type of dimer is favored regardless of the type of auxiliary ligands attached to the ruthenium.
\r\n\r\nThe change in the optical spectrum upon raising the pH indicated a pKa of 10.32 for the dimer. This, taken in conjunction with the infrared, the raman and the nmr results indicated that the dimer was \u00b5-oxo bridged at low pH and was, most likely, \u00b5-oxo, \u00b5-hydroxo bridged at higher pH.
\r\n\r\nWhen an excess of Ce(IV) was added to a solution of the dimer the catalytic evolution of dioxygen was observed. The dimer also catalyzed the disproportionation of hydrogen peroxide.
\r\n\r\nSection II describes the electrochemistry of Ru(III)edta and the dimer. Cyclic voltammetry, polarography and rotating ring-disk electrode (RRDE) voltammetry were used to characterize the oxidation and reduction of each of the two complexes. The electrochemical oxidation of Ru3Y produced the dimer after one Faraday per two moles of ruthenium. The catalytic evolution of dioxygen was also observed at a platinum electrode. The step-wise reduction of the dimer to produce Ru(II)edta is also described. The combined use of the RRDE with digital simulations of the mechanism of reduction yielded the rate constants for the rate of breakup of the intermediates. A spectro-electrochemical experiment also showed that the dimer can be oxidized further to produce a Ru(IV)-Ru(IV) dimer.
", "doi": "10.7907/bh22-fp76", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:781", "collection": "thesis", "collection_id": "781", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02272006-082939", "primary_object_url": { "basename": "Winkler_jr_1984.pdf", "content": "final", "filesize": 5584065, "license": "other", "mime_type": "application/pdf", "url": "/781/1/Winkler_jr_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Spectroscopy and Photochemistry of Metal-Oxo Complexes", "author": [ { "family_name": "Winkler", "given_name": "Jay Richmond", "orcid": "0000-0002-4453-9716", "clpid": "Winkler-Jay-Richmond" } ], "thesis_advisor": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Collins", "given_name": "Terrence J.", "clpid": "Collins-T-J" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Electronic spectroscopic, photophysical, and photochemical investigations of two types of metal-oxo complexes are described. The electronic absorption spectra of various molybdenyl ions (MoO3+ were measured in crystals and solutions. These spectra clearly support 2B1(x2-y2) \u2190 2B2(xy) and 2E(xz, yz) \u2190 2B2(xy) assignments for the two weak bands near 25,000 and 14,000 cm-1, respectively, in these molecules. A Franck-Condon analysis of the 2B1 \u2190 2B2 band in the 5 K single crystal absorption spectrum of (Ph4As)MoOCl4 indicated a 0.07(1) \u00c5 elongation of the metal-chloride bond in the excited state. Crystalline (Ph4As)MoOCl4 luminesces from the lower energy component of a split 2E(xz, yz) state with a lifetime of 160 ns at 300 K, increasing to 1.4 \u00b5s at 5 K. No luminescence was detected from any molybdenyl ion in solution.
\r\n\r\nThe electronic absorption and emission spectra of trans-ReO2L4z (L = CN-, z = 3-; L = 1/2(ethylenediamine), z = +; L = pyridine, z = +; L = 4-picoline, z = +; L = 4-t-butylpyridine, z = +) were also measured in crystals and solutions. The lowest energy absorption bands are assigned to components of a split 3Eg[(eg)1(b2g)1] state (ground state 1Ag1g[(b2g)2]). Emission from at least two of these components was identified in the cyanide and pyridine complexes and only the ethylenediamine complex failed to luminesce. Franck-Condon analyses of the emission spectra indicated ca. 0.1 \u00c5 elongations of each Re-O bond in the 3Eg excited states. The lifetime of the 3Eg state varies from 10 to 300 \u00b5s in crystals and is ca. 10 \u00b5s for trans-ReO2L4z species in aprotic solvents. Protons efficiently quench the luminescence of these molecules. Experiments directed toward photoinduced oxygen atom transfer chemistry are also described.
\r\n", "doi": "10.7907/DE5E-2Y69", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:11285", "collection": "thesis", "collection_id": "11285", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11272018-091510836", "primary_object_url": { "basename": "Lee_C-W_1984.pdf", "content": "final", "filesize": 32975907, "license": "other", "mime_type": "application/pdf", "url": "/11285/1/Lee_C-W_1984.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Adsorption and Electrochemistry of BIS-1, 10-Phenanthroline Complexes of Copper (I,II) and Fungal Laccase A", "author": [ { "family_name": "Lee", "given_name": "Chi-Woo", "orcid": "0000-0002-0821-9344", "clpid": "Lee-Chi-Woo" } ], "thesis_advisor": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis is an outcome of the efforts directed toward the theme \"Electrocatalysis of dioxygen reduction by copper- containing molecules adsorbed on graphite electrodes.\"
\r\n\r\nIn the first part, an electrochemical measurement of the rate of electron exchange between Cu(phen)2+ adsorbed on graphite and Cu(phen)2++ in solution is described. The rate constant was estimated to be ca. 105 M-1 s-1 by using rotating disk voltammetry. The origin of the previously reported but widely discrepant values (5 x 107 M-1 s-1 and 50 M-1 s-1) in the literature is discussed, and a new estimate of ca. 104 M-1 s-1 is obtained by applying Marcus theory in a form that allows explicitly for differences in reorganization energy between the oxidized and reduced halves of the reacting redox couples. The electrocatalytic studies of dioxygen reduction by Cu(phen)2+ could not be done due to the low signal-to-noise ratio.
\r\n\r\nIn the second part, the bioelectrocatalytic reduction of molecular oxygen by reduced fungal laccase A immobilized on pyrolytic graphite is described. The reduction produces exclusively water in the potential range studied (< 0 V vs. SSCE). The catalytic activity reaches its maximum at pH 3~4, and the lower limit on rate constant for the reduction in this pH range was estimated to be 1.5 x 104 M-1 s-1.
\r\n\r\nThree appendices describe (i) potential step hydrodynamic chronocoulometry, (ii) a new method to determine the self- exchange rate constant for the redox couple in which the coordination numbers depend on the oxidation states, and (iii) a novel electrochemical method of detecting H2O2.
\r\n", "doi": "10.7907/f4sv-x904", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:11296", "collection": "thesis", "collection_id": "11296", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12072018-114316546", "type": "thesis", "title": "The Total Synthesis of the Enantiomer of Lasalocid A", "author": [ { "family_name": "Fitzsimmons", "given_name": "Brian Joseph", "clpid": "Fitzsimmons-Brian-Jopseph" } ], "thesis_advisor": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "thesis_committee": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Ireland", "given_name": "Robert E.", "clpid": "Ireland-R-E" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A convergent total synthesis of the enantiomer of the\r\nnaturally occurring polyether antibiotic Lasalocid A (X-537A) and preliminary results of the biological testing of this compound are reported.
\r\n", "doi": "10.7907/w5gn-5650", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:11263", "collection": "thesis", "collection_id": "11263", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10312018-105602325", "primary_object_url": { "basename": "Buttry_DA_1984.pdf", "content": "final", "filesize": 44477528, "license": "other", "mime_type": "application/pdf", "url": "/11263/1/Buttry_DA_1984.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Effects of Electron Exchange on the Photochemical, Electrochemical and Electrocatalytic Responses of Polymer Modified Electrodes ", "author": [ { "family_name": "Buttry", "given_name": "Daniel Alan", "orcid": "0000-0002-6915-6914", "clpid": "Buttry-Daniel-Alan" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Janda", "given_name": "Kenneth C.", "clpid": "Janda-K-C" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A spectroelectrochemical method is presented which may be used to measure the concentrations of the two oxidation states of a redox couple in a polymer film. The method is applied to Ru(bpy)32+ in Nafion films on transparent tin oxide electrodes. Measurements of the emission of this complex in Nafion films on graphite and tin oxide electrodes are used to obtain information about the quenching of Ru(bpy)32+* by Ru(bpy)33+. Features of the luminescence which yield insight into the structure of the Nafion film are discussed.
\r\n\r\nExperiments are described which bear on the question of when electron self-exchange reactions can contribute to the propagation of electrons through polymer films on electrodes. The results of experiments on the Co(bpy)32+/+ couple are discussed in terms of a theory derived by Dahms and Ruff et al. which describes the contribution of electron self-exchange reactions to diffusion in mixtures containing both halves of a redox couple.
\r\n\r\nThe propagation of charge through polymer films by electron exchange cross-reactions between different redox couples which are co-incorporated into a polymer film on an electrode is discussed. Two experimental examples of this phenomenon are presented.
\r\n\r\nAn electrocatalytic application of a polymer modified electrode is described. Cobalt tetraphenylporphyrin is incorporated into a Nafion film on a graphite electrode, and this porphyrin is used to catalyze the two-electron electroreduction of dioxygen. Enhanced catalytic currents are observed when an electron mediator (Ru(NH3)63+) is added to the film. This mediator serves to shuttle electrons between the electrode and the relatively immobile catalyst sites. The performance of electrocatalysts in polymer films is discussed with emphasis on ways to enhance stability without sacrificing efficiency.
", "doi": "10.7907/x5vq-d546", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:9937", "collection": "thesis", "collection_id": "9937", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10072016-152635305", "primary_object_url": { "basename": "DURAND_RR_1984.pdf", "content": "final", "filesize": 36878103, "license": "other", "mime_type": "application/pdf", "url": "/9937/1/DURAND_RR_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Catalysis of the Electroreduction of Dioxygen by Monomeric and Dimeric Cobalt Porphyrins", "author": [ { "family_name": "Durand", "given_name": "Richard Raymond, Jr.", "clpid": "Durand-Richard-Raymond" } ], "thesis_advisor": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" } ], "thesis_committee": [ { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Schaefer", "given_name": "William P.", "clpid": "Schaefer-W-P" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Mechanistic aspects of the catalytic electroreduction of dioxygen by monomeric and dimeric cobalt porphyrins were investigated. The catalysts were examined while either adsorbed to graphite electrodes or dissolved in concentrated acids.
\r\n\r\nMonomeric cobalt(II) porphyrins adsorbed to graphite electrodes were found to reduce dioxygen to hydrogen peroxide. Cyclic and rotating disk voltammetry were used to examine the kinetics and mechanism of the catalyzed reactions. These monomeric catalysts exhibited behavior atypical of simple redox catalysis.
\r\n\r\nThe mechanisms by which the reduction of dioxygen at graphite electrodes is catalyzed by cofacial dicobalt and related porphyrins has been investigated. The products of the reductions, the electrode potential where the reduction proceeds and the mechanistic role of protons were among the topics examined. A comparison of the behavior of several new cofacial metalloporphyrins has led to a more detailed proposal for the mechanisms by which they operate.
\r\n\r\nMonomeric and dimeric cobalt porphyrins have been dissolved in trifluoromethanesulfonic acid (5.6 M) and concentrated phosphoric acid without demetalation. The electrocatalytic reduction of dioxygen by solutions of the catalysts was examined by rotating disk and ring-disk voltammetry. The dissolved metalloporphyrins provide improved stability to the catalysts.
\r\n\r\nThe reaction of a cobalt(II) complex with superoxide was examined electrochemically in a non-aqueous electrolyte. The affinity of superoxide for cobalt(II) has been demonstrated by cyclic voltammetry. The results of this study were related to mechanisms of dioxygen reduction in aqueous media.
", "doi": "10.7907/h738-ft41", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:429", "collection": "thesis", "collection_id": "429", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02012005-160716", "type": "thesis", "title": "Spectroscopy, Electrochemistry, and Photochemistry of Polynuclear Metal-Metal Bonded Complexes", "author": [ { "family_name": "Nocera", "given_name": "Daniel George", "orcid": "0000-0001-5055-320X", "clpid": "Nocera-Daniel-George" } ], "thesis_advisor": [ { "family_name": "Collins", "given_name": "Terrence J.", "clpid": "Collins-T-J" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Janda", "given_name": "Kenneth C.", "clpid": "Janda-K-C" }, { "family_name": "Collins", "given_name": "Terrence J.", "clpid": "Collins-T-J" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The spectroscopic, electrochemical, and photochemical properties of two d4 metal polynuclear complex systems were investigated: the quadruple bond complex, Re2Cl82-, and the M6X142- halide cluster ions of molybdenum(II) and tungsten (II).
\r\n\r\nThe vibrationally structured luminescence spectrum of Re2Cl82- at 5 K has confirmed that emission arises from the \u03b4\u03b4* singlet state. Both Re2Cl82- and electronically excited Re2Cl82- (Re2Cl82-*) undergo facile one-electron oxidation and reduction reactions. Aromatic amines quench Re2Cl82-* luminescence and a Marcus analysis of the steady state quenching rate constants suggest that Re2Cl83-|D+ is formed in the quenching reaction and that the ion-pair decays rapidly by back electron transfer. The luminescence of Re2Cl82-* is also quenched by electron acceptors (TCNE and chloranil) in nonaqueous solutions, forming Re2Cl8- and reduced acceptor. The back electron transfer reactions are near the diffusion controlled limit. Electrochemical measurements suggested that photogenerated Re2Cl8- anion could be trapped by Cl- to produce Re2Cl92-, thereby circumventing the efficient back reaction. Irradiation (\u03bb > 600 nm) of nonaqueous solutions of Re2Cl82- and chloranil or TCNE in the presence of excess Cl- does, indeed, produce Re2Cl92- in quantitative yield. Photolysis reactions employing a quencher (e.g. 2,3-dichloro-5,6-dicyano-benzoquinone) possessing a redox couple with a potential greater than that of Re2Cl9-/2- (0.53 vs. SCE) yielded Re2Cl9- as a final product. Thus, a single low energy photon facilitates a two-electron oxidation of Re2Cl82-. Direct two-electron oxidation of Re2Cl82-* by chlorine atom transfer reagents such as PtCl62- to produce Re2Cl9- was also attempted. Irradiation (\u03bb > 590 nm) of dichloromethane solutions containing Re2Cl82- and PtCl62- quantitatively yield Re2Cl9-. Qualitative kinetic experiments measuring the wavelength dependence of the reaction rate suggest that the photochemical reaction proceeds by a free radical pathway involving the 3A2u ligand field excited state of PtCl62- and does not involve an atom transfer reaction mechanism. These experiments are not without their ambiguities, however, and further areas of research are discussed. The crystal structure analysis of NBu4Re2Br9 is also presented.
\r\n\r\nThe M6X142- (M=Mo,W; X=Cl,Br,I) ions are intensely luminescent in the solid state and solution and the photophysical properties of the six cluster ions are documented. These results in conjunction with those of the EPR spectra of the electrochemically generated M6X14- anions are discussed in terms of recent theoretical models for the electronic structure of the cluster ions. Electrochemical experiments were also conducted and showed the M6X142- cluster ions to undergo reversible single-electron oxidation reactions. For Mo6Cl142- a quasi-reversible one-electron reduction wave was observed in addition to its oxidation wave. The electrochemical and photophysical properties of Mo6Cl142- suggested electrogenerated chemiluminescent behavior of the cluster ion. Emission, characteristic of Mo6Cl142-*, is observed upon electrochemical generation of Mo6Cl14- and Mo6Cl143-.
\r\n", "doi": "10.7907/T14G-4N32", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:11887", "collection": "thesis", "collection_id": "11887", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11042019-130341164", "primary_object_url": { "basename": "willett-bc-1983.pdf", "content": "final", "filesize": 9129463, "license": "other", "mime_type": "application/pdf", "url": "/11887/1/willett-bc-1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Electron Transfer Rates and Adsorption in the Electrochemistry of Cobalt-2,2'-Bipyridine, Ruthenium Ammine Thiocyanate Complexes and cis-[(C\u2085H\u2085)Fe(CO)P(C\u2086H\u2085)\u2082]\u2082", "author": [ { "family_name": "Willett", "given_name": "Brian Christopher", "clpid": "Willett-Brian-Christopher" } ], "thesis_advisor": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" } ], "thesis_committee": [ { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In Part I of this thesis, the electrochemical properties of cobalt(I)-2,2'-bipyridine and cobalt(I)-6,6'-dimethyl-2,2'-bipyridine complexes were investigated, including their reactions with reducible substrates and their adsorption on mercury electrodes.
\r\n\r\nElectron transfer rate constants measured for cyclooctatetraene and cis-[(C5H5)Fe(CO)P(C6H5)2]2, molecules which undergo large intramolecular rearrangements upon electron transfer, in non-aqueous solvents with various tetraalkylammonium salts as supporting electrolytes are presented in Part II. The electrode kinetics were measured by cyclic voltammetry, chronocoulometry and AC impedance techniques. Values of the rate constants found were as large as 0.30 cm/sec.
\r\n\r\nSynthesis and adsorption behavior of several novel substituted ruthenium ammine complexes are discussed in Part III. The adsorption on mercury was used to distinguish between the two thiocyanate linkage isomers, Ru(NH3)5NCS2+ and Ru(NH3)5SCN2+. The coordination properties of ruthenium(II) were used to prepare trans-Ru(NH3)4(NCS))4-vinyl- pyridine)Ru(EDTA), a binuclear ruthenium species.
", "doi": "10.7907/t7fp-5z02", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:11883", "collection": "thesis", "collection_id": "11883", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11012019-171533510", "primary_object_url": { "basename": "paffett-mt-1983.pdf", "content": "final", "filesize": 5134072, "license": "other", "mime_type": "application/pdf", "url": "/11883/1/paffett-mt-1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Electrochemistry of Molybdenum Aquo Ions", "author": [ { "family_name": "Paffett", "given_name": "Mark Thomas", "clpid": "Paffett-Mark-Thomas" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Marcus", "given_name": "Rudolph A.", "orcid": "0000-0001-6547-1469", "clpid": "Marcus-R-A" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The electrochemical behavior of selected molybdenum aquo ions in acidic media is examined in relation to solution structure.
\r\n\r\nThe electrochemistry of Mo(VI) in non-complexing aqueous electrolytes is usually severely complicated by the oligomerization and subsequent adsorption of the reactant. This problem can be circumvented by employing dilute (\u2264 10-4 M) solutions of Mo(VI) in 1 to 2 M trifluoromethanesulfonic acid. Under these conditions staircase voltammograms and pulse polarograms exhibit single, reversible waves that are consistent with the one-electron reduction of an unadsorbed, monomeric Mo(VI) species. The pH dependence of the reduction potentials suggests that two protons are consumed in the reduction of each Mo(VI). The monomeric Mo(V) reduction product undergoes spontaneous dimerization with a rate constant estimated as 103 M-1 s-1. It also reduces perchlorate and nitrate anions at a significant rate.
\r\n\r\nThe Mo2(V)/Mo2(III) redox couple in acidic solution involves an overall four electron-six proton transfer connecting the two participants. This redox process is characterized by extreme electrochemical irreversibility. Reduction of the Mo2(V) aquo ion to the Mo2(III) aquo ion proceeds with \u03b1na equal to 0.73 and a proton reaction order of 1.4. A chemical step with an inverse dependence on proton concentration precedes the reoxidation of aquo Mo2(III) to aquo Mo2(V). Plausible mechanisms are given for these observations.
\r\n\r\nThe trinuclear ions containing Mo(IV), Mo3O4(H2O)4+9(Mo3(IV)) and an oxalato derivative, Mo3O4(C2O4)3(H2O) 2-3, can be reversibly reduced in acidic media to trinuclear Mo(III) species. The reductions involve two sequential electron transfer steps with formal potentials that are pH dependent:
\r\n\r\n[chemical equations; see abstract in scanned thesis for details].
\r\n\r\nTwo waves are evident in voltammograms and polarograms of Mo3O4(C2O4)3(H2O)2-3 but with Mo3(IV) the two formal potentials are too close together to observe separate waves. However, logarithmic analysis of the shapes of normal pulse polarograms allowed the two formal potentials to be evaluated. The reductions of both complexes are believed to be accompanied by protonation of the bridging and capping oxo-ligands. The new, trinuclear Mo3(III) species resulting from the three-electron reduction of Mo3(IV) exhibits a characteristic EPR spectrum. The mixed-valent intermediate, Mo3(III, III, IV), is diamagnetic. Possible structural changes that accompany the addition of electrons and protons to Mo3IV) are discussed.
", "doi": "10.7907/hv5n-dz91", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3462", "collection": "thesis", "collection_id": "3462", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09112006-133416", "primary_object_url": { "basename": "Stone_at_1983.pdf", "content": "final", "filesize": 13629658, "license": "other", "mime_type": "application/pdf", "url": "/3462/1/Stone_at_1983.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Reduction and Dissolution of Manganese(III) and (IV) Oxides by Organics", "author": [ { "family_name": "Stone", "given_name": "Alan Thomas", "orcid": "0000-0002-3660-1129", "clpid": "Stone-Alan-Thomas" } ], "thesis_advisor": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "List", "given_name": "John A.", "clpid": "List-J-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Although it is known that manganese oxides are solubilized by reduction in anoxic waters, the chemical processes are poorly understood. A study of the reduction and dissolution of manganese oxide suspensions by twenty-seven organic substrates that have chemical structures similar to those of natural organics was undertaken to determine the rates and mechanisms of the solubilization reactions.
\r\n\r\nDissolution of suspensions by hydroquinone in the pH range 6.5 < pH < 8.5 is described by the following experimental rate law:
\r\n\r\n(d[Mn2+])/dt = k1{H+}0.46[HQ]1.0(MnT - [Mn2+])
\r\n\r\nwhere [Mn2+] is the amount of dissolved manganese, [HQ] is the hydroquinone concentration, and MnT is the initial amount of manganese oxide. The apparent activation energy of the reaction was found to be +37 kJ/mole. The Mn(III,IV) oxide suspension was prepared by oxidizing a Mn(OH)2(s.) suspension with oxygen, and has a composition characterized by MnO1.66. Suspension particles were between 0.2 and 1.0 microns in diameter. Calcium and phosphate were found to inhibit the dissolution reaction, by adsorbing on the oxide surface.
\r\n\r\nDihydroxybenzenes and methoxyphenols dissolved the suspensions at appreciable rates. Of the aliphatic substrates examined, only ascorbate, oxalate, and pyruvate dissolved the oxide. Dissolution by marine fulvic acid was found to be photocatalyzed.
\r\n\r\nA model was developed to explain the observed rate dependence and the relative reactivity of different organic substrates. The model assumes that complexes between substrate and surface sites form prior to electron transfer and dissolution. The pH dependence is not explained by this model; involvement of H+ in the dissolution of reduced surface sites may be responsible for the observed fractional order with respect to H+.
\r\n", "doi": "10.7907/MSQ2-M609", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:11785", "collection": "thesis", "collection_id": "11785", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09032019-101145351", "primary_object_url": { "basename": "Dodge_JA_1983.pdf", "content": "final", "filesize": 58253946, "license": "other", "mime_type": "application/pdf", "url": "/11785/1/Dodge_JA_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Synthesis and Characterization of Binuclear Copper(I) Complexes as Models for Protein Active Sites", "author": [ { "family_name": "Dodge", "given_name": "John Austin", "clpid": "Dodge-John-Austin" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Marsh", "given_name": "Richard Edward", "clpid": "Marsh-R-E" }, { "family_name": "Gagne", "given_name": "Robert R.", "clpid": "Gagne-Robert-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A series of coordinatively unsaturated copper(I) complexes of binucleating nitrogenous ligands have been examined as potential models for protein active sites. The first complex discussed is derived from the ligand N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN). The binuclear copper(I) complex Cu2(TPEN)2+ reversibly binds two equivalents of carbon monoxide, giving an adduct which displays a pair of CO stretching absorptions at 2097 and 2107 cm-1. Both Cu2(TPEN)(BF4)2 and its carbonyl adduct have been examined by single-crystal X-ray diffraction. Each copper atom of Cu2(TPEN)2+ is bound in a highly asymmetric environment, with an intramolecular copper-copper separation of 2.78\u00c5. In the carbonyl adduct the metal-ligand bonds have rearranged, each copper has assumed a pseudotetrahedral geometry, and there is no longer any direct metal-metal interaction.
\r\n\r\nAnother complex, Cu2(CHXNpy)2+, has been prepared with a ligand analogous to TPEN, but with trans-1,2-cyclohexanediamine substituted for ethylenediamine. A second cyclohexanediamine-based ligand, CHXNbim, has been prepared which contains four benzimidazole groups rather than pyridine. Both Cu2(CHXNpy)2+ and Cu2(CHXNbim)2+ exhibit temperature dependent proton magnetic resonance spectra. The fact that fast exchange is observed only well above room temperature, in spite of the high lability of copper(I), is attributed to the sterically constrained nature of the ligands. Like Cu2(TPEN)2+, Cu2(CHXNpy)2+ forms a dicarbonyl adduct, but it is of lower stability. The benzimidazole complex Cu2(CHXNbim)2+ does not react with carbon monoxide and reacts only slowly with oxygen. Furthermore, unlike Cu2(TPEN)2+ and Cu2(CHXNpy)2+, Cu2(CHXNbim)2+ shows no tendency to disproportionate. This high stability is likely due to a combination of steric and electronic factors, which are discussed.
\r\n\r\nFinally, a series of complexes having different xylylene \"backbones\" have been synthesized and examined. Each ligand contains four biologically relevant imidazole groups. All of the complexes react rapidly with carbon monoxide and oxygen (irreversibly in the latter case). In contrast with another known xylylene-based complex containing pyridine groups, the reaction with oxygen occurs without ligand hydroxylation. Factors which could contribute to the reactivity difference are discussed.
", "doi": "10.7907/v7jq-zn64", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:10882", "collection": "thesis", "collection_id": "10882", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05142018-155247666", "primary_object_url": { "basename": "Dow_WC_1982.pdf", "content": "final", "filesize": 34736989, "license": "other", "mime_type": "application/pdf", "url": "/10882/1/Dow_WC_1982.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Total Synthesis of \u03b2-Chamigrene", "author": [ { "family_name": "Dow", "given_name": "William Clinton", "clpid": "Dow-William-Clinton" } ], "thesis_advisor": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "thesis_committee": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Ireland", "given_name": "Robert E.", "clpid": "Ireland-R-E" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Dougherty", "given_name": "Dennis A.", "orcid": "0000-0003-1464-2461", "clpid": "Dougherty-D-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A total synthesis of the sesquiterpene (\u00b1)-\u03b2-Chamigrene is described. A key step is the preparation of spiroketone ii through Claisen rearrangement of the vinyl-substituted cycloheptapyran i. A modified Meinwald-Cava ring contraction sequence is used for the intramolecular elaboration of a functionalized one-carbon unit at the hindered alpha flank of the spirocycle. This procedure affords ester iii. Alternate reaction pathways available to the reactive ketene intermediate are also discussed. These results are compared with observations made in a previously reported synthesis of aphidicolin.
\r\n\r\n[Chemical structure included in scanned thesis' abstract, p. iv.]
", "doi": "10.7907/6kmn-mt31", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:11122", "collection": "thesis", "collection_id": "11122", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07132018-094917474", "type": "thesis", "title": "Electrochemistry of Some Rhodium(I) Complexes", "author": [ { "family_name": "Najdzionek", "given_name": "Jan Stanley", "clpid": "Najdzionek-Jan-Stanley" } ], "thesis_advisor": [ { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Janda", "given_name": "Kenneth C.", "clpid": "Janda-K-C" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The electrochemistry of Rh[C6H5)2P(CHx)nP(C6H5)2]2 Y where Y = CF3SO-3 or ClO-4, x = 2 with n = 1, 2, 3, 4 and x = 1 with n = 2 was examined and compared with that of Co[(C6H5)2P(CHx)2P(C6H5)2]2 where x = 1 and 2. Cyclic voltammetric (CV), chronoamperometric (CA), polarographic (including D.C., normal and differential pulse) and bulk electrolytic experiments were performed and the results show that all of these Rh(I) phosphine complexes are reduced in a two-electron process.
\r\n\r\nCV and CA measurements were used to determine the heterogeneous electron transfer rate constants for Rh[(C6H5)2P(CH2)2P(C6H5)2]2. The values determined were 0.0092 and 0.0087 cm/sec, respectively, and the results are discussed in relation to the Butler-Volmer formulation of electrode kinetics.
\r\n\r\nFluorescence measurements were made on the above rhodium complexes for n = 1, 3 and 4 at room temperature and at 77 K. None emit under ambient conditions in solution but the compound containing ligands with a single methylene unit backbone emitted at 77 K with a lifetime of 20 microseconds. The UV-Visible spectrum of reduced Rh(DPP)+2, the most stable of the reduced complexes, displayed a very intense absorption at 450 nm which was assumed to be charge-transfer in origin.
\r\n\r\nThe two-electron reduction of Rh2(2,5-dimethyl-2,5-diisocyanohexane)2+4 produced a unique species in which a CN- ion has been lost resulting in the formation of a cyclohexylimine ligand which bridges the metal atoms through the imine function. The strain imposed on the TMB ligand backbone forces the rhodium atoms to have the strongest interaction of any of the Rh(Br)+4 compounds studied [Rh(l)-Rh(2) = 2.970(1)\u00c5]. Linear isocyanide carbon-nitrogen distances range from 1.153(9) to 1.175(9) \u00c5 while the imine carbon-nitrogen is extended slightly to 1.254(9) \u00c5.
", "doi": "10.7907/pqye-xp04", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3362", "collection": "thesis", "collection_id": "3362", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-143724", "type": "thesis", "title": "A Study of the Adsorption of Ni(II) onto an Amorphous Silica Surface by Chemical and NMR Methods", "author": [ { "family_name": "Young", "given_name": "James Robert", "clpid": "Young-James-Robert" } ], "thesis_advisor": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "thesis_committee": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The physical structure of the electrical double layer at a metal-oxide surface is not well-known. Adsorption models, which require a knowledge of the location of the adsorbed species, have integrated different descriptions of the electrical double layer into a common coordination chemistry framework.
\r\n\r\nThe goal of this work was to determine the hydration number of Ni(II) species adsorbed unto a silica surface by extending a nuclear magnetic resonance (NMR) technique used to determine the hydration number of paramagnetic metal ions in solution. Information about the environment of the adsorbed Ni(II) species at the molecular level could then be incorporated into state-of-the-art adsorption models.
\r\n\r\nIn order to conduct the NMR experiment, it was necessary to determine the speciation of a Ni(II)-silica system at a high metal-ion loading. Titrations, in 0.1 N NaClO4, were conducted on silica suspensions, nickel solutions and a system where the total amount of Ni(II) was twice the total number of available surface binding sites. The pH dependence of the adsorption process and the maximum adsorption density achievable were investigated.
\r\n\r\nThe amount of charge on a silica surface was found to increase logarithmically with pH. Formation of surface complexes with Na+ provided the necessary mechanism to account for this behavior. All of the Ni(II) present in the Ni(II)-silica system was removed by adsorption processes at a pH of approximately 8. In the same system, removal of Ni(II) by a precipitation process does not occur until Ni(OH)2(s) forms at a pH of approximately 8.5. The adsorption process was not limited by the number of surface hydroxyl groups present. It was shown that the NiOH moiety of a hydrolyzed nickel surface complex could provide the new adsorption centers necessary for a multilayer adsorption process, if the NiOH group functions chemically like an SiOH group. The observation of adsorption of Ni(II) onto a silica surface at coverages greater than one monolayer indicates siliceous soils and sediments may have a greater capacity to bind Ni(II) than previously thought.
\r\n\r\nThe capability of the NMR spectroscopic technique to determine hydration numbers of adsorbed metal ions was demonstrated. Usefulness of the technique was limited by the slowness of water exchange between the first coordination sphere of the adsorbed Ni(II) species and bulk solution. A lower limit for the hydration number of the adsorbed Ni(II) species was calculated to be 4.4. This is at the lower end of the predicted range for this value (4.5 to 6.0). Suggestions were made to improve upon the design of the NMR experiment so as to overcome the limitations encountered.
", "doi": "10.7907/Q574-CG34", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:11119", "collection": "thesis", "collection_id": "11119", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07122018-160904951", "type": "thesis", "title": "Transition Metal Complexes of 1, 3-bis (2'-pyridylimino) Isoindolines and Their Use as Alcohol Oxidation Catalysts", "author": [ { "family_name": "Marks", "given_name": "David Neil", "clpid": "Marks-David-Neil" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Gagne", "given_name": "Robert R.", "clpid": "Gagne-Robert-R" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Bercaw", "given_name": "John E.", "clpid": "Bercaw-J-E" }, { "family_name": "Marsh", "given_name": "Richard Edward", "clpid": "Marsh-R-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Condensation of 1, 2-dicyanobenzene and 2-amino-4-methylpyridine resulted in the formation of a ligand, 4'-MeLH, which in its anionic or neutral form functions as a tridentate chelate. Metal complexes were prepared with metal to ligand ratios of 1:1 and 1:2. The 1:1 complexes also contain acetate or chlorides as ligands while in the 1:2 complex the two tridentate ligands provide a pseudooctahedral environment about the metal ion. An analogous binucleating ligand was prepared by reaction of 1, 2, 4, 5-tetracyanobenzene and 2-amino-4-s-butylpyridine. This ligand, as a dianion, is capable of binding two metal ions, providing three coordination sites for each. Complexes were prepared in which the remaining coordination sites are either occupied by 4'-MeLH, resulting in two six-coordinate metal ions, or by an acetate ligand. Mononuclear and binuclear complexes were prepared with Mn(II), Fe(II), Co(II), Co(III), Ni(II), Cu(II), Zn(II), Ru(II), and Ru(III). Mixed-metal complexes containing Ru(II) were also prepared. Magnetic, spectral and electrochemical properties of these molecules were investigated.
\r\n\r\nThe ruthenium complex, (4'-MeLH)RuCl3, catalyzes the autoxidation of alcohols in basic alcoholic solution. The reaction is general, resulting in the oxidation of primary and secondary alcohols, with the principal products being aldehydes and ketones. The catalytic reaction is affected by the strength of the base used and its coordinating ability. The best results were obtained using sodium ethoxide as a base. Turnover numbers of 10-30 per day were observed in one atmosphere of oxygen at ambient temperature; with larger turnover numbers at higher temperatures. More than 200 turnovers were observed in the oxidation of ethanol at the ambient temperature with little or no loss of catalytic activity. Dimeric complexes of Ru(II) and Ru(III) were isolated from ethanolic solutions. These complexes were characterized and their role in the catalytic reaction is discussed.
\r\n\r\nThe Ru(III) complex, (4'-MeLH)RuCl3, also catalyzes the electrochemical oxidation of alcohols in basic alcoholic solution. The best results were obtained with 2, 6-lutidine as the base. The electrochemical oxidation was carried out at a carbon electrode immersed in an alcoholic solution at 0.8-1.0 V vs. nhe. In the absence of catalyst, negligible current was observed. The catalyzed electrochemical oxidation was general, oxidizing primary and secondary alcohols, with the principal products being aldehydes and ketones. More than 20 catalytic cycles were completed with the current remaining at 75% of its initial value. The Ru(III) complex exhibits reversible one-electron oxidation waves in nonalcoholic solvents in the presence or absence of 2, 6-lutidine. The electrochemistry in alcohols and nonalcohols is discussed, and a possible pathway for the catalytic electrochemical oxidation is presented.
\r\n\r\n", "doi": "10.7907/swwe-jf28", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:10854", "collection": "thesis", "collection_id": "10854", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05072018-163009985", "primary_object_url": { "basename": "Eigenberg_KE_1981.pdf", "content": "final", "filesize": 94653881, "license": "other", "mime_type": "application/pdf", "url": "/10854/1/Eigenberg_KE_1981.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Interaction of Chlorophyll \u03b1 with Lipids in Model and Natural Membrane Systems", "author": [ { "family_name": "Eigenberg", "given_name": "Kenneth Eugene", "clpid": "Eigenberg-Kenneth-Eugene" } ], "thesis_advisor": [ { "family_name": "Raftery", "given_name": "Michael A.", "clpid": "Raftery-M-A" } ], "thesis_committee": [ { "family_name": "Raftery", "given_name": "Michael A.", "clpid": "Raftery-M-A" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Richards", "given_name": "John H.", "clpid": "Richards-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Chlorophyll a is the principal photosynthetic pigment of plants and most algae. Despite its importance relatively little is known about its organization or environment within the photosynthetic membrane. A variety of evidence suggests that a significant portion of the chlorophyll may be associated with the lipid portion of the photosynthetic thylakoid membrane. The topic of the interaction of chlorophyll with lipid membranes, both model and natural, forms the basis of this thesis.
\r\n\r\nIt is found that chlorophyll a can be incorporated into model phospholipid bilayer membranes at up to 40 mole percent. Both multilamellar and small vesicular bilayer forms can be prepared and characterized. The phase diagram of the chlorophyll a/distearoylphosphatidylcholine (DSPC) bilayer system, obtained by differential thermal analysis, is complex and indicates that below the solidus phase transition chlorophyll a and DSPC form a compound phase with a composition of 40 mole pe-rcent chlorophyll a. A thermodynamic simulation of the phase diagram yields an estimate for the strength of the chlorophyll a-DSPC interaction. Nuclear magnetic resonance studies, utilizing the shift effect on nearby nuclei due to the large ring current magnetic anisotropy of chlorophyll, demonstrate that compound formation results from a coordination interaction between the DSPC phosphate and the central magnesium atom of chlorophyll a which has an obligatory requirement for an additional axial ligand.
\r\n\r\nThe optical properties of chlorophyll a are modified by its inclusion into bilayers and change at the bilayer phase transition. Compared to chlorophyll a in organic solution, chlorophyll a in bilayers has absorption maxima which are strongly red-shifted and a greatly reduced fluorescence. The red-shift is most pronounced and fluorescence is lowest below the solidus phase transition temperature. Several possible causes of these changes in optical properties are discussed. Because the optical properties of chlorophyll a/DSPC bilayers in the compound phase duplicate the optical properties of bulk in vivo chlorophyll quite well, this system constitutes an attractive model of the photosynthetic chlorophyll antenna.
\r\n\r\nEvidence for the location of a pool of chlorophyll in a lipid environment comes from the 13C-NMR spectrum at 90.5 MHz of the photosynthetic thylakoid membrane from spinach. Specific lipid and chlorophyll resonances are observed and assigned but no protein resonances are found. It can be estimated that at least 30% of the plant chlorophyll contributes to the high resolution spectrum with the remainder presumably broadened by association with membrane proteins. The resonance linewidths of the observed chlorophyll phytol chains are approximately the same as those of the lipid hydrocarbon chains indicating that their motional states are similar and suggesting that this fraction of chlorophyll is lipid bound or at most only loosely associated with membrane proteins.
", "doi": "10.7907/p7ns-0z05", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:4968", "collection": "thesis", "collection_id": "4968", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12122006-111302", "primary_object_url": { "basename": "Sung_w_1981.pdf", "content": "final", "filesize": 3860878, "license": "other", "mime_type": "application/pdf", "url": "/4968/1/Sung_w_1981.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Catalytic Effects of the \u03b3-FeOOH (Lepidocrocite) Surface on the Oxygenation Removal Kinetics of the Fe(II) and Mn(II)", "author": [ { "family_name": "Sung", "given_name": "Windsor", "clpid": "Sung-Windsor" } ], "thesis_advisor": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "thesis_committee": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "North", "given_name": "Wheeler J.", "clpid": "North-W-J" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" } ], "local_group": [ { "literal": "W. M. Keck Laboratory of Hydraulics and Water Resources" }, { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nPrevious investigations of Fe(II) oxygenation had resulted in a wide range in the reported rate constant(s). While Fe(II) oxygenation rates are fast in simple laboratory systems (seconds to minutes when pH > 7), actual rates observed in natural waters can be orders of magnitude lower. Conversely, while Mn(II) oxygenation rates are slow in laboratory systems (days when pH < 9), much faster rates are observed in natural waters or implicated in model studies.\r\n\r\nThe influences of ionic strength, temperature and anions on the Fe(II) homogeneous oxygenation rates were examined in this study. Other rate constants from the literature were successfully incorporated into this framework. Complexation by major anions (e.g., [...] and [...]) and ionic strength effects were sufficient to account for the retardation of Fe(II) oxygenation in seawater. Autocatalysis of Fe(II) oxygenation was observed for pH > 7. A general integrated autocatalytic rate expression suitable for Fe(II) or Mn(II) oxygenation was used to interpret laboratory-obtained kinetic data. Oxidation of Fe(II) in various laboratory systems with characteristics like those of natural water was shown to form the allotrope [gamma]-FeOOH. The [gamma]-FeOOH surface was shown to be an excellent catalyst for Fe(II) and Mn(II) oxygenation.\r\n\r\nThe [gamma]-FeOOH surface obtained by oxidizing milli-molar levels of Fe(II) in 0.7 M NaCl was studied in the following ways: surface charge characteristics by acid/base titration; adsorption of Mn(II) and surface oxidation of Mn(II). A rate law was formulated to account for the effects of pH and the amount of surface on the surface oxidation rate of Mn(II). The presence of milli-molar levels of [gamma]-FeOOH was shown to reduce significantly the half-life of Mn(II) in 0.7 M NaCl from hundreds of hours to hours. The [gamma]-FeOOH surface was shown to be as effective as colloidal MnO2 in catalysing Mn(II) oxygenation.", "doi": "10.7907/r22w-2c12", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:4015", "collection": "thesis", "collection_id": "4015", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10102006-110816", "primary_object_url": { "basename": "Liljestrand_hm_1980.pdf", "content": "final", "filesize": 4666320, "license": "other", "mime_type": "application/pdf", "url": "/4015/1/Liljestrand_hm_1980.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Atmospheric Transport of Acidity in Southern California by Wet and Dry Mechanisms", "author": [ { "family_name": "Liljestrand", "given_name": "Howard Michael", "clpid": "Liljestrand-Howard-Michael" } ], "thesis_advisor": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "thesis_committee": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Jennings", "given_name": "Paul C.", "clpid": "Jennings-P-C" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Acid precipitation samples collected at Pasadena, California, from February 1976 to April 1979 and at eight other southern California sites for shorter periods were analyzed to determine acid and base composition. The concentrations of major cations (H+, NH4+, Na+, K+, Ca2+, Mg2+) and anions (Cl-, NO2-, Br-, NO3-, SO42) as well as trace weak acids (Fe, Al, Mn, Si(OH)4, RCOOH) were determined. Titrations with base showed acidity predominantly to be due to strong acids (nitric and sulfuric) and weak acids (ammonium ion and carbonic acid). The pH was controlled by strong acidity at the urban sites in the Los Angeles Basin.\r\n\r\nThe chemical composition of precipitation samples collected in ~0.25 in increments is modeled in several ways. Chemical balances are used to determine the contributions of sea salt, soil dust, stationary sources, mobile sources and non-point sources of ammonia. Multiple regression analysis is used to relate ground-level measurements of air quality and atmospheric conditions with rainwater nitrite plus nitrate and sulfate concentrations. Precipitation intensity, ozone, nitric oxide and nitrogen dioxide concentrations are most strongly correlated with rainwater nitrite plus nitrate. Precipitation intensity, ozone, and nitric oxide are most strongly correlated with rainwater sulfate.\r\n\r\nGas-liquid equilibrium models yield the following predictions: Low partial pressures of ammonia (average of 0.001 - 0.006 ppbv within the basin) during precipitation scavenging; total sulfite amounting to less than 25% of the non-sea salt sulfur; and nitrite concentrations from NO and NO2 dissolution which are slightly larger than observed values. Kinetic models of the formation of nitrate and sulfate underestimate the observed concentrations. Spatial distributions of acids and base correspond with local sources. The mountain sites and the more rural eastern sites have significantly less net acidity than the western urban sites.\r\n\r\nEstimates of the dry deposition of atmospheric acids indicate the dry flux is ~6600 equivalents/HA-YR in the Los Angeles Basin compared to ~380 equivalents/HA-YR for the wet flux of strong acidity. The semi-arid climate and high ambient pollutant concentrations cause the large dry flux. Advection of pollutants is the most important mechanism for the removal of acidity from the Los Angeles airshed.\r\n", "doi": "10.7907/pgev-yh86", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:1310", "collection": "thesis", "collection_id": "1310", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04082008-084228", "primary_object_url": { "basename": "Orlowski_te_1979.pdf", "content": "final", "filesize": 13116909, "license": "other", "mime_type": "application/pdf", "url": "/1310/1/Orlowski_te_1979.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "New Techniques in Coherent Optical Spectroscopy: Optical Dephasing and Radiationless Processes in Molecules", "author": [ { "family_name": "Orlowski", "given_name": "Thomas Edward", "clpid": "Orlowski-Thomas-Edward" } ], "thesis_advisor": [ { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" } ], "thesis_committee": [ { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Robinson", "given_name": "G. Wilse", "clpid": "Robinson-G-W" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "McKoy", "given_name": "Basil Vincent", "clpid": "McKoy-B-V" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe objectives of this thesis are to develop new high-resolution (\u00b1 3 MHz) coherent nonlinear optical spectroscopic techniques and to utilize them to examine the nature of line broadening processes in optical transitions of isolated large and small molecules. By measuring the coherent and incoherent transients observed either in the forward direction along the laser beam (absorption) or at right-angles to the exciting beam (emission), these techniques allow one to determine optical [...] (the longitudinal relaxation time) and optical [...] (the transverse relaxation time). From [...] and [...] one can obtain under certain circumstances, both the radiative and nonradiative [...] contributions as well as the pure dephasing [...] contribution to the total homogeneous linewidth [...] of the optical transition.\r\n\r\nTwo molecules are examined in detail. Iodine was chosen to demonstrate the new techniques because its conventional spectroscopy is well-known and to examine dephasing and decay processes important for small molecules. It was studied in the gas phase and in a molecular beam. Condensed phase experiments were performed on single crystals of pentacene isolated in a p-terphenyl host to obtain information about the nature of radiationless transitions and dephasing processes important in this large molecule.\r\n\r\nThe optical transition that was studied in iodine is [...]. Using LADS (Laser Acoustic Diffraction Spectroscopy) for obtaining nanosecond time resolution with a narrowband single-mode dye laser and the IRD (Incoherent Resonance Decay) method whereby population dynamics and the coherence in the system can be obtained by monitoring the spontaneous emission, the following Stern-Volmer relationship was obtained for iodine:\r\n\r\n[...] = (0.783 \u00b1 0.032) + (0.0143 \u00b1 0.0005) P(mtorr).\r\n\r\nThis relationship provides a zero-pressure radiative lifetime of 1.28 \u00b1 0.05 [...]sec and a nonradiative collisional quenching cross section of [...] = 70 \u00b1 2 [...]. These results agree with those obtained in previous studies with broadband excitation indicating that excitation bandwidth is unimportant for [...] processes in small molecules. Using the electrooptic method of laser frequency switching, an optical nutation was observed in iodine whose Rabi oscillation frequency [...] provided the dipole moment for the transition ([mu] = 0.05 Debye) after determining the laser field amplitude [...]. The Rabi frequency was also obtained from a coherent oscillation observed on top of the IRD signal in iodine at low pressure. This oscillation decayed by [...] and the overall IRD signal provided [...] such that both the coherence and decay of the system were obtained simply by monitoring the spontaneous emission. The homogeneous linewidth of the transition was measured using the 3-pulse photon echo method. At 10 mtorr pressure it was found to be 579 kHz. This is almost three orders of magnitude less than the inhomogeneous (Doppler) linewidth of ca. 400 MHz. Molecular beam experiments provided the radiative lifetime (1.24 \u00b1 0.02 [...]sec) of iodine in a collisionless environment from which the radiative contribution (22%, 128 kHz) to the total homogeneous linewidth was obtained. Assuming that radiative losses from the lower level of the system can be neglected it was also determined that 38 kHz (7%) of the homogeneous linewidth is due to non-radiative relaxation (inelastic scattering) and a dramatic 413 kHz (71%) is due to pure dephasing [...] as a result of elastic scattering processes. Finally an OFID (optical free induction decay) was observed in the molecular beam whose decay indicated that [...]. Therefore, in a collisionless environment, the only dephasing process for iodine is spontaneous emission (i.e., no intramolecular dephasing processes exist).\r\n\r\nThe optical transition that was studied in pentacene [...] exhibits four sites in a p-terphenyl host. The lowest energy site at 16,887 cm[...] has the following characteristics at 1.8[...]K:\r\n\r\n[...] = 24.9 \u00b1 2 nsec; [...] = 44 \u00b1 2 nsec, and [mu] = 0.7 \u00b1 0.1 Debye.\r\n\r\nExperiments in this system are categorized into two time regimes for theoretical analysis: a transient coherence regime where the observed decay is comparable with [...] and [...], and a steady-state coherence regime where transient dephasing is complete and the off-diagonal elements of the density matrix have decayed to their steady-state values in the presence of the laser field. The Wilcox-Lamb method is used to derive rate equations ([...] dependent) from the density matrix equations of motion. These equations describe the population dynamics in the pentacene level structure ([...] = ground state, [...] = excited singlet state and [...] = triplet manifold) and upon averaging them over the inhomogeneous linewidth of the transition and then using them to fit experimental decay curves one obtains:\r\n\r\n[...] = 24.9 \u00b1 2 nsec and [...] = 15.7 [...]sec,\r\n\r\nthe time constants for spontaneous emission to [...] and crossing into [...], respectively. OFID and nutation expressions are presented for the pentacene level structure and when appropriate averaging is done over both the inhomogeneous linewidth and the laser beam spatial profile, good fits can be obtained for the experimental transients. At 1.8[...]K it was determined that [...] = [...]. Therefore, as in iodine at zero pressure, spontaneous emission is the only dephasing process in pentacene at low temperature. At higher temperature, however, a strongly temperature dependent dephasing process takes place with an onset at 3.7[...]K. A theoretical treatment of the various dephasing channels is presented that explains the observed temperature dependence of [...] in pentacene and attributes pure dephasing to an anisotropy in the scattering amplitudes between the ground and excited states. Optical site selection of the pentacene transitions has been observed and is related to vibrational relaxation and homogeneous and inhomogeneous broadening in this system. Studies of the homogeneous broadening of the vibronic line 267 cm[...] above the lowest energy site indicate that vibrational relaxation is fast (psec) in the excited singlet manifold of pentacene. Finally from more than ten independent experiments including narrow and broad band excitation, on- and off-resonance scattering, Zeeman effect measurements and the transient decay as a function of excess energy in the molecule, a more complete picture of the pentacene level structure is given. It is proposed that the slow decay\t[...] observed during narrowband excitation represents intersystem crossing to nearby triplet manifolds after the transient coherence of the \"two-level\" system [...] has decayed. Furthermore, the decay of the primary state prepared in these experiments is not sensitive to the bandwidth or the coherence properties of the excitation source.\r\n", "doi": "10.7907/1KE1-7557", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:929", "collection": "thesis", "collection_id": "929", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03112009-074718", "primary_object_url": { "basename": "Pankow_jf_1979.pdf", "content": "final", "filesize": 5776308, "license": "other", "mime_type": "application/pdf", "url": "/929/1/Pankow_jf_1979.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Dissolution Rates and Mechanisms of Tetragonal Ferrous Sulfide (Mackinawite) in Anoxic Aqueous Systems", "author": [ { "family_name": "Pankow", "given_name": "James Frederick", "clpid": "Pankow-James-Frederick" } ], "thesis_advisor": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "thesis_committee": [ { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Revel", "given_name": "Jean-Paul", "clpid": "Revel-J-P" }, { "family_name": "Duwez", "given_name": "Pol E.", "clpid": "Duwez-P-E" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nAn experimental study was carried out on the rates and mechanisms of the non-oxidative dissolution of mackinawite (tetragonal FeS) in anoxic aqueous systems of varying pH (3-7), T (5-35\u00b0C), and ionic strength (0.05-0.60 M [M is underscored]). A special glass and teflon dissolution reactor was constructed. The main design criterion was the need to keep the reaction medium absolutely free of oxygen.\r\n\r\nThe flux F[subscript S] (moles/cm[superscript 2]-min) from the surfaces of pellets pressed from [...]l\u03bc FeS particles was found to obey the rate equation\r\n\r\nF[subscript S] = k[subscript 1]a[subscript H superscript +] + k[subscript 2]\r\n\r\nk[subscript 1] and k[subscript 2] are rate constants and a[subscript H superscript +] is the activity of the hydrogen ion At 25\u00b0C, k[subscript 1] = 0.22 cm/min with a relative standard deviation of 18%. The value of k[subscript 2] was measured to be 1.9 moles/cm[superscript 2]-min with a relative standard deviation of 22%. The actual exposed FeS surface area A[...] was related to the projected area A by the expression A[...] = 1.7A. The factor of 1.7 accounts for the roughness of the surface. The actual rate constants k[...] and k[...] were therefore obtained by dividing k[subscript 1] and k[subscript 2] by 1.7: k[...] = 0.13/min and k[...] = 1.1 x 10[superscript -9] moles/cm[superscript 2]-min. The k[...] term dominates at pH < 4.3 and k[...]dominates at pH > 5.6. pH 4.3-5.6 is a transition region.\r\n\r\nIt is argued that these rate constants are relatable to dissolution mechanisms at the FeS crystal surface. k[...] is envisioned to arise from an attack at the surface by H[superscript +]. k[...] is linked to a mechanism which relies upon normal thermal vibrations and H20 solvation effects to liberate lattice constituents. Both k[\u2026] and k[\u2026] are thought to reflect a rate-limiting departure of surficial S(-II) lattice constituents. The activation entropies [...] for these two processes are calculated accordingly. The activation enthalpies [\u2026] were determined from the E[subscript a] data. Concentrations of Cu(II) in the ppm range were found to strongly inhibit the dissolution rate.\r\n\r\nThe k[...] term would dominate at pH's typical of natural waters. This term was used to determine how quickly FeS dissolves when anaerobic sediments are disturbed. When anoxic and oxic sediments are adjacent to one another, the dissolution of FeS in the anoxic portion takes place primarily near the oxic front.\r\n\r\nIf FeS-containing anaerobic sewage sludge is discharged to anoxic receiving waters, the particles of FeS may be expected to dissolve. Expressions were developed by which the lifetimes of such particles may be calculated. Both transport and non-transport controlled situations are analyzed. The effects which the agglomeration of such FeS with other sewage particles would have on the dissolution rate were considered. The implications which this work holds for sediment pyritization rates were also discussed.\r\n", "doi": "10.7907/31FS-0Q87", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:11305", "collection": "thesis", "collection_id": "11305", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12102018-143101993", "primary_object_url": { "basename": "Williams_Roger_M_1979_CIT_thesis_.pdf", "content": "final", "filesize": 4975836, "license": "other", "mime_type": "application/pdf", "url": "/11305/1/Williams_Roger_M_1979_CIT_thesis_.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Crystallographic Order and Disorder in Quasi-One-Dimensional Conductors", "author": [ { "family_name": "Williams", "given_name": "Roger Macauley", "clpid": "Williams-Roger-Macauley" } ], "thesis_advisor": [ { "family_name": "Samson", "given_name": "Sten Otto", "clpid": "Samson-Sten-Otto" }, { "family_name": "Gordon", "given_name": "Joseph", "clpid": "Gordon-Joseph" } ], "thesis_committee": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Vaughan", "given_name": "Robert W.", "clpid": "Vaughan-R-W" }, { "family_name": "Gagne", "given_name": "Robert R.", "clpid": "Gagne-Robert-R" }, { "family_name": "Gordon", "given_name": "Joseph", "clpid": "Gordon-Joseph" }, { "family_name": "Samson", "given_name": "Sten Otto", "clpid": "Samson-Sten-Otto" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Stacked, conducting isocyanide complexes of rhodium(I) were synthesized and characterized by x-ray diffraction and electrical measurements. Good crystals of orthorhombic [Rh(CNCHCH2)4]ClO4, with a0 = 8.81 \u00c5, b0 = 22.85 \u00c5, c0 = 12.70 \u00c5, were obtained and a structural refinement was carried out in space group Immm. The rhodium chain is nearly uniform (Rh-Rh = 2.94 \u00c5) and ligands and anions show considerable disorder. The room temperature conductivity is -2 \u03a9-1 cm-1 and conductivity is activated. The moderately high conductivity of [Rh(CNCHCH2)4]ClO4 is due to the presence of a low-lying conduction band rather than a non-integral rhodium oxidation state.
\r\n\r\nThe disorder, tetragonal phase of (TTF)Clx, a0 = 11.19 \u00c5, c0 = 3.60 \u00c5, was studied for compositions x = 0.67, x = 0.70. A room\r\ntemperature structural refinement in space group P42/mnm revealed eclipsed stacking of TTF cations and extremely high disorder of chlorides in channels. Low temperature studies revealed ordering of chloride ions for both compositions. (TTF)Cl0.67 undergoes an incomplete structural transition to a monoclinic symmetry phase at ~250\u00b0 K. Ordering of chloride ions occurs at the same temperature. Fast cooling (>1\u00b0 K/hr) results in peak broadening which is apparently due to the very small size of diffracting domains within the crystal. Both small domain size and the inequivalent environments of TTF cations following chloride ordering may contribute to the drop in conductivity observed at the phase transition.
\r\n\r\nStructural refinements of both the subcell (space group Cmca, a0 = 18.47 \u00c5, b0 = 4.95 \u00c5, c0 = 18.30 \u00c5) and full cell (space group Pmc2l, a0 = 18.47 \u00c5, b0 = 9.90 \u00c5, c0 = 18.30 \u00c5) of a low disorder crystal of TTT2I3 were carried out. The iodine chain is highly disordered and all sites have less than full occupancy. The presence of I3- and I2 species in the chain is likely. The resulting aperiodic potential due to the iodide chain may be expected to be retained at low temperature and inhibit a metal-to-insulator transition.
\r\n\r\nElectrochemical crystal-growth experiments involving TTF, TMTSF, and HMTSF gave successful results with the first two donors. Crystals of (TMTSF)Br0.8 and (TMTSF)(SCN)0.5 are isostructural, although the latter exhibits satellite reflections (period = 4.6 x c0) in diffraction patterns. Both structures were refined in space group Cmcm, and the satellite data of (TMTSF)(SCN)0.5 was modeled in space group Cmc2l. Unit cell parameters are a a0 = 9.798 \u00c5, b0 = 23.837 \u00c5, c0 = 7.095 \u00c5, for the bromide and a0 = 9.919 \u00c5, b0 = 24.124 \u00c5, c0 = 7.220 \u00c5, for the thiocyanate. The planes of these cations are perpendicular to the z-axis and consecutive cations slip back and forth by ~1.3 \u00c5 to reduce methyl group steric repulsion.
\r\n\r\nAll of the systems studied are single carrier conductors with conduction along the cation stack and high disorder of anions. The nature of the disorder and its relationship to phase transitions, as well as interchain coupling and stacking in the cation chain, were evaluated in these compounds. Comparison of (TTF)Cl0.67 and (TTT02I3 were especially useful, as both exhibit comparably very short range order of halide ions at room temperature, but different cation stacking arrangements (eclipsed and slipped, respectively) and hence different interchain coupling and electronic bandwidth.\r\nStructural studies at room temperature and low temperature provided an opportunity to understand the important differences in the electrical properties of these two materials.
", "doi": "10.7907/FPJF-PM42", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:10768", "collection": "thesis", "collection_id": "10768", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03092018-170506721", "primary_object_url": { "basename": "Abel_RH_1971.pdf", "content": "final", "filesize": 34829886, "license": "other", "mime_type": "application/pdf", "url": "/10768/1/Abel_RH_1971.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Electrode Kinetic Studies Using a Computerized Data Acquisition and Analysis System", "author": [ { "family_name": "Abel", "given_name": "Roger Henry", "clpid": "Abel-Roger-Henry" } ], "thesis_advisor": [ { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" } ], "thesis_committee": [ { "family_name": "Kuppermann", "given_name": "Aron", "clpid": "Kuppermann-A" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Chan", "given_name": "Sunney I.", "clpid": "Chan-S-I" }, { "family_name": "Roberts", "given_name": "John D.", "clpid": "Roberts-J-D" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The first section of this dissertation introduces the basic concepts that are necessary for the quantitative description of electrode kinetics. The refinements and corrections in the rate equation that are due to a detailed model of the electrical double layer, and to the potential step relaxation technique are introduced and discussed.
\r\n\r\nA discussion of the non-linear statistical analysis techniques that are necessary for a rigorous analysis of rate equation is presented in the second section. The estimates of the precision of the desired parameters obtained by using statistical methods can be used as a measure of the efficiency of an experiment. Their use as measures of \"kinetic information density\" is developed and illustrated by comparing charge and current measurement in the potential step technique. Previous approaches to the subject of \"kinetic information density\" are discussed and compared to the results from statistical analysis.
\r\n\r\nThe third section describes the computerized data acquisition and analysis system that was designed and used for the study of electrode kinetics.
\r\n\r\nThe final section presents the results of the kinetic studies undertaken on the Zn+2/Zn(Hg) system in 1 F NaNO3, 1 F NaClO4, and 1 F NaCl supporting electrolytes. Ensemble averaging is used in these studies to increase precision and its values is illustrated.
\r\n\r\nThe results that are obtained for the rate constants in the various supporting electrolytes are compared and it is shown that the rates are comparable in NaNO3 and NaClO4 supporting electrolytes but significantly greater in 1 F NaCl. These results are compared with results of previous investigators and the quality of the results of this thesis are compared to those of previous investigators.
", "doi": "10.7907/HT2Z-3059", "publication_date": "1971", "thesis_type": "phd", "thesis_year": "1971" }, { "id": "thesis:1072", "collection": "thesis", "collection_id": "1072", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03232006-153024", "type": "thesis", "title": "Infrared Absorption Associated with Strong Hydrogen Bonds", "author": [ { "family_name": "Albert", "given_name": "Norman Edward", "clpid": "Albert-Norman-Edward" } ], "thesis_advisor": [ { "family_name": "Badger", "given_name": "Richard McLean", "clpid": "Badger-R-M" } ], "thesis_committee": [ { "family_name": "Davidson", "given_name": "Norman R.", "clpid": "Davidson-N-R" }, { "family_name": "Anson", "given_name": "Fred C.", "clpid": "Anson-F-C" }, { "family_name": "Badger", "given_name": "Richard M.", "clpid": "Badger-R-M" }, { "family_name": "King", "given_name": "Robert Burnett", "clpid": "King-R-B" }, { "family_name": "Robinson", "given_name": "G. Wilse", "clpid": "Robinson-G-W" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The hydrogen bond systems in potassium hydrogen fluoride, acetamide hemihydrochloride, nickel dimethylglyoxime, potassium hydrogen bis-phenylacetate and maleic acid were studied via infrared spectroscopy between 5000 cm-1 and 400 cm-1. Each compound was studied in detail by the potassium bromide pressed disc technique.
\r\n\r\nThe infrared active fundamentals of the bifluoride ion were found to be shifted from the values reported for the pure, crystalline compound. Integral absorption intensities of the two infrared active fundamentals in the KBr solid solution were evaluated and interpreted in terms of the effective charge motion.
\r\n\r\nSpectra of acetamide hemihydrochloride, nickel dimethylglyoxime and potassium hydrogen bis-phenylacetate exhibited unusual features: an intense, extremely broad background absorption between 2000 cm-1 and 400 cm-1 and a deep \"window\" in the broad background. Maleic acid, however, was found to give a normal, well-behaved spectrum. These unusual features have been interpreted in terms of the symmetry of the hydrogen bond and the complexity of the hydrogen bonded molecules. The broad background is regarded as the superposition of several hydrogen bond vibrational modes, each of which is anharmonically coupled with low frequency intermolecular vibrational modes. The \"windows\" have been explained on the basis of a special perturbation between certain vibrational energy levels of the hydrogen bond modes and the molecular group modes in a small fraction of the molecules; in a majority of the molecules the perturbation is either absent or is very weak. It is suggested that these features are characteristic of short symmetric hydrogen bonds in complex molecules.
", "doi": "10.7907/JACR-N881", "publication_date": "1961", "thesis_type": "phd", "thesis_year": "1961" } ]