Tang, Jieyu and Sukhanov, Andrey A. and Wei, Min and Zhang, Xue and Zhao, Jianzhang and Dick, Bernhard and Voronkova, Violeta K. and Li, Ming-De (2025) Thionated Coumarins: Study of the Intersystem Crossing and the Zero-field Splitting of the Triplet State Using Time-Resolved Transient Optical and Electron Paramagnetic Resonance Spectroscopies. CHEMISTRY-A EUROPEAN JOURNAL, 31 (21): e202404589. ISSN 0947-6539, 1521-3765
Full text not available from this repository. (Request a copy)Abstract
To study the effect of thionation of the carbonyl groups in a chromophore, i. e. replacing the O atom with S atom, on the photophysics, we studied two thionated coumarin derivatives (Cou-S and Cou-6-S) with various steady state and transient spectroscopic methods. Both compounds exhibit red-shifted absorption (up to 4900 cm-1) and strong fluorescence quenching as compared to the unthionated analogues. Femtosecond transient absorption spectra show fast ISC (ca. 10 ps) in the thionated coumarin derivatives, while negligible ISC was observed in the unthionated coumarin. Interestingly, triplet excited state lifetimes of the thionated coumarin (0.14 mu s) is much shorter than the unthionated analogues (53.4 mu s). Time-resolved electron paramagnetic resonance (TREPR) spectra indicate much larger zero field splitting (ZFS) D parameters (up to 0.287 cm-1) for the T1 state of the thionated coumarins than the unthionated analogues (D=0.1001 cm-1). This large D value is attributed to the strong spin orbital coupling effect. These results demonstrate the advantage and the drawback of thionation-enhanced ISC, i. e. the ISC is efficient, but triplet state lifetimes become substantially shorter. This information is useful for the future design of heavy atom-free triplet photosensitizers for photodynamic therapy, photon upconversion, photocatalytic organic synthesis and photopolymerization, etc.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PHOTON UP-CONVERSION; CYCLOMETALATED IR(III) COMPLEXES; AROMATIC CARBONYL MOLECULES; ATOM-FREE PHOTOSENSITIZERS; EXCITED-STATE; PHOTOPHYSICAL PROPERTIES; CHARGE-TRANSFER; PHOTODYNAMIC THERAPY; BODIPY DERIVATIVES; FLUORESCENT-PROBES; Triplet state; Electron spin polarization; Intersystem crossing; Transient Absorption; Transient EPR |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) > Prof. Dr. Bernhard Dick |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 07 May 2026 04:50 |
| Last Modified: | 07 May 2026 04:50 |
| URI: | https://pred.uni-regensburg.de/id/eprint/67297 |
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