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Long‐Lived Charge‐Transfer State Induced by Spin‐Orbit Charge Transfer Intersystem Crossing (SOCT‐ISC) in a Compact Spiro Electron Donor/Acceptor Dyad
Author(s) -
Liu Dongyi,
ElZohry Ahmed M.,
Taddei Maria,
Matt Clemens,
Bussotti Laura,
Wang Zhijia,
Zhao Jianzhang,
Mohammed Omar F.,
Di Donato Mariangela,
Weber Stefan
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202003560
Subject(s) - intersystem crossing , chemistry , photoexcitation , electron donor , electron transfer , acceptor , photochemistry , triplet state , electron paramagnetic resonance , ultrafast laser spectroscopy , excited state , atomic physics , singlet state , nuclear magnetic resonance , physics , spectroscopy , quantum mechanics , biochemistry , condensed matter physics , catalysis
We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer ( 3 CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the 3 NI* state. Then the slow secondary CS (125 ns) gives the long‐lived 3 CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1 NI*→ 1 CT→ 3 NI*→ 3 CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory.