Zhang, Xue and Sukhanov, Andrey A. and Liu, Xi and Taddei, Maria and Zhao, Jianzhang and Harriman, Anthony and Voronkova, Violeta K. and Wan, Yan and Dick, Bernhard and Di Donato, Mariangela (2023) Origin of intersystem crossing in highly distorted organic molecules: a case study with red light-absorbing N,N,O,O-boron-chelated Bodipys. CHEMICAL SCIENCE, 14 (19). pp. 5014-5027. ISSN 2041-6520, 2041-6539
Full text not available from this repository. (Request a copy)Abstract
To explore the relationship between the twisted pi-conjugation framework of aromatic chromophores and the efficacy of intersystem crossing (ISC), we have studied a N,N,O,O-boron-chelated Bodipy derivative possessing a severely distorted molecular structure. Surprisingly, this chromophore is highly fluorescent, showing inefficient ISC (singlet oxygen quantum yield, phi<INF>Delta</INF> = 12%). These features differ from those of helical aromatic hydrocarbons, where the twisted framework promotes ISC. We attribute the inefficient ISC to a large singlet-triplet energy gap (Delta E<INF>S<INF>1</INF>/T<INF>1</INF></INF> = 0.61 eV). This postulate is tested by critical examination of a distorted Bodipy having an anthryl unit at the meso-position, for which phi<INF>Delta</INF> is increased to 40%. The improved ISC yield is rationalized by the presence of a T<INF>2</INF> state, localized on the anthryl unit, with energy close to that of the S<INF>1</INF> state. The electron spin polarization phase pattern of the triplet state is (e, e, e, a, a, a), with the T<INF>z</INF> sublevel of the T<INF>1</INF> state overpopulated. The small zero-field splitting D parameter (-1470 MHz) indicates that the electron spin density is delocalized over the twisted framework. It is concluded that twisting of pi-conjugation framework does not necessarily induce ISC, but S<INF>1</INF>/T<INF>n</INF> energy matching may be a generic feature for increasing ISC for a new-generation of heavy atom-free triplet photosensitizers.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | TRIPLET EXCITED-STATE; INTRAMOLECULAR CHARGE-TRANSFER; PHOTOINDUCED ELECTRON-TRANSFER; ANNIHILATION UP-CONVERSION; SINGLET OXYGEN; VISIBLE-LIGHT; FRANCK-CONDON; PHOTOSENSITIZERS; EFFICIENT; DYADS |
| 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: | 20 Mar 2024 07:25 |
| Last Modified: | 20 Mar 2024 07:25 |
| URI: | https://pred.uni-regensburg.de/id/eprint/60544 |
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