[
    {
        "id": "authors:ad6sm-ys307",
        "collection": "authors",
        "collection_id": "ad6sm-ys307",
        "cite_using_url": "https://authors.library.caltech.edu/records/ad6sm-ys307",
        "type": "article",
        "title": "Prolonging All-Optical Molecular Electron Spin Coherence in the Tissue Transparency Window",
        "author": [
            {
                "family_name": "Sutcliffe",
                "given_name": "Erica",
                "orcid": "0009-0008-7307-551X",
                "clpid": "Sutcliffe-Erica"
            },
            {
                "family_name": "Rothbaum",
                "given_name": "Jacob O.",
                "orcid": "0000-0002-4337-2184",
                "clpid": "Rothbaum-Jacob-O"
            },
            {
                "family_name": "Aalto",
                "given_name": "Jonathan P.",
                "clpid": "Aalto-Jonathan-P"
            },
            {
                "family_name": "Whiteside",
                "given_name": "Juliette C.",
                "orcid": "0009-0002-1620-6532",
                "clpid": "Whiteside-Juliette-C"
            },
            {
                "family_name": "Hadt",
                "given_name": "Ryan G.",
                "orcid": "0000-0001-6026-1358",
                "clpid": "Hadt-R-G"
            }
        ],
        "abstract": "<p>Coherent electron spin states within paramagnetic molecules hold significant potential for microscopic quantum sensing. However, all-optical coherence measurements amenable to high spatial and temporal resolution under ambient conditions remain a significant challenge. Here we conduct room-temperature, picosecond time-resolved Faraday ellipticity/rotation (TRFE/R) measurements of the electron spin decoherence time&nbsp;<em>T</em><sub class=\"stack\">2</sub><sup class=\"stack\">*</sup>&nbsp;in [IrBr<sub>6</sub>]<sup>2&ndash;</sup>. Decoherence is strongly sensitive to solution phase viscosity, pointing to molecular tumbling as an important decoherence mechanism. Accordingly, immobilization of [IrBr<sub>6</sub>]<sup>2&ndash;</sup> molecules in thin polymer films results in an order-of-magnitude increase in coherence lifetime and significantly greater magnetic field sensitivity. By tuning energies of ligand-to-metal charge transfer (LMCT) states, TRFE/R enables spin initialization and readout in the tissue transparency window, paving the way toward all-optical, ultrafast molecular electron spin coherence imaging in biological systems.</p>",
        "doi": "10.1021/jacs.5c13180",
        "issn": "0002-7863",
        "publisher": "American Chemical Society",
        "publication": "Journal of the American Chemical Society",
        "publication_date": "2025-09-24",
        "series_number": "38",
        "volume": "147",
        "issue": "38",
        "pages": "34244-34248"
    },
    {
        "id": "authors:rsv9m-nm769",
        "collection": "authors",
        "collection_id": "rsv9m-nm769",
        "cite_using_url": "https://authors.library.caltech.edu/records/rsv9m-nm769",
        "type": "article",
        "title": "A Spectrochemical Series for Electron Spin Relaxation",
        "author": [
            {
                "family_name": "Kazmierczak",
                "given_name": "Nathanael",
                "orcid": "0000-0002-7822-6769",
                "clpid": "Kazmierczak-Nathanael-P"
            },
            {
                "family_name": "Xia",
                "given_name": "Kay",
                "orcid": "0000-0003-4526-1733",
                "clpid": "Xia-Kelly-T"
            },
            {
                "family_name": "Sutcliffe",
                "given_name": "Erica",
                "orcid": "0009-0008-7307-551X",
                "clpid": "Sutcliffe-Erica"
            },
            {
                "family_name": "Aalto",
                "given_name": "Jonathan",
                "orcid": "0009-0007-9764-226X",
                "clpid": "Aalto-Jonathan-P"
            },
            {
                "family_name": "Hadt",
                "given_name": "Ryan G.",
                "orcid": "0000-0001-6026-1358",
                "clpid": "Hadt-R-G"
            }
        ],
        "abstract": "<p>Controlling the rate of electron spin relaxation in paramagnetic molecules is essential for contemporary applications in molecular magnetism and quantum information science. However, the physical mechanisms of spin relaxation remain incompletely understood, and new spectroscopic observables play an important role in evaluating spin dynamics mechanisms and structure&ndash;property relationships. Here, we use cryogenic magnetic circular dichroism (MCD) spectroscopy and pulse electron paramagnetic resonance (EPR) in tandem to examine the impact of ligand field (d&ndash;d) excited states on spin relaxation rates. We employ a broad scope of square-planar Cu(II) compounds with varying ligand field strength, including CuS<sub>4</sub>, CuN<sub>4</sub>, CuN<sub>2</sub>O<sub>2</sub>, and CuO<sub>4</sub>&nbsp;first coordination spheres. An unexpectedly strong correlation exists between spin relaxation rates and the average d&ndash;d excitation energy (<em>R</em><sup>2</sup> = 0.97). The relaxation rate trends as the inverse 11th power of the excited-state energies, whereas simplified theoretical models predict only an inverse second power dependence. These experimental results directly implicate ligand field excited states as playing a critical role in the ground-state spin relaxation mechanism. Furthermore, ligand field strength is revealed to be a particularly powerful design principle for spin dynamics, enabling formation of a spectrochemical series for spin relaxation.</p>",
        "doi": "10.1021/jacs.4c16571",
        "publisher": "American Chemical Society",
        "publication": "Journal of the American Chemical Society",
        "publication_date": "2025-01-22",
        "series_number": "3",
        "volume": "147",
        "issue": "3",
        "pages": "2849\u20132859"
    }
]