Pei, Yuying and Sukhanov, Andrey A. and Chen, Xi and Iagatti, Alessandro and Doria, Sandra and Dong, Xin and Zhao, Jianzhang and Li, Yanqin and Chi, Weijie and Voronkova, Violeta K. and Di Donato, Mariangela and Dick, Bernhard (2025) The Photophysics of Naphthalimide-Phenoselenazine Electron Donor-Acceptor Dyads: Revisiting the Heavy-Atom Effect in Thermally Activated Delayed Fluorescence. CHEMISTRY-A EUROPEAN JOURNAL, 31 (5). ISSN 0947-6539, 1521-3765
Full text not available from this repository. (Request a copy)Abstract
We prepared thermally activated delayed fluorescence (TADF) emitter dyads, NI-PTZ, NI-PTZ-2Br and NI-PSeZ, with naphthalimide (NI) as electron acceptor and 10H-phenothiazine (PTZ) or 10H-phenoselenazine (PSeZ) as electron donor to study the heavy-atom effect on the intersystem crossing (ISC) and reverse ISC (rISC) in the TADF emitters. The delayed fluorescence lifetimes of the dyads containing heavy atoms ( tau DF ${{\tau }_{{\rm D}{\rm F}}}$ =5.9 mu s for NI-PSeZ and tau DF ${{\tau }_{{\rm D}{\rm F}}}$ =16.5 mu s for NI-PTZ-2Br, respectively) are longer than the heavy atom-free counterpart NI-PTZ ( tau DF ${{\tau }_{{\rm D}{\rm F}}}$ =2.0 mu s). Nanosecond transient absorption (ns-TA) spectral study and the time-resolved electron paramagnetic resonance (TREPR) spectra show the presence of both 3LE and 3CS states. These findings represent solid experimental evidences for the spin-vibronic coupling mechanism of TADF. Moreover, the ns-TA spectra show that the heavy atoms don't have a significant effect since the lifetime of the triplet transient species (1.3 mu s for NI-PTZ) is not shortened in their presence (4.5 mu s for NI-PSeZ and 5.3 mu s for NI-PTZ-2Br). These results show that the previously claimed heavy-atom effect on rISC and TADF is not a universal principle. The femtosecond transient absorption (fs-TA) spectra of the compounds indicate the occurrence of fast charge separation within 1-2 ps, and the charge recombination is slow (>4 ns)
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | INTRAMOLECULAR CHARGE-TRANSFER; TRIPLET EXCITED-STATES; TIME-RESOLVED EPR; SEPARATED STATES; PARAMAGNETIC-RES; ORGANIC EMITTERS; PHENOTHIAZINE; SINGLET; RECOMBINATION; EFFICIENCY; heavy-atom effect; intersystem crossing; reverse intersystem crossing; thermally activated delayed fluorescence; time resolved electron paramagnetic resonance |
| 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: | 31 Mar 2026 08:33 |
| Last Modified: | 31 Mar 2026 08:33 |
| URI: | https://pred.uni-regensburg.de/id/eprint/65287 |
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