Long‐Lived Charge‐Transfer State Induced by Spin‐Orbit Charge Transfer Intersystem Crossing (SOCT‐ISC) in a Compact Spiro Electron Donor/Acceptor Dyad. (8th May 2020)

• Record Type: Journal Article
• Authors: Liu, Dongyi; El‐Zohry, Ahmed M.; Taddei, Maria; Matt, Clemens; Bussotti, Laura; Wang, Zhijia; Zhao, Jianzhang; Mohammed, Omar F.; Di Donato, Mariangela; Weber, Stefan
• Is Part Of: Angewandte Chemie. Volume 132:Number 28(2020)
• Page Start: 11688
• Page End: 11696
• Publication Date: 2020-05-08
• Subjects: charge transfer -- electron spin control -- intersystem crossing -- time-resolved EPR -- triplet state; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202003560
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: 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. Abstract : A rigid, simple, spiro compact electron donor/acceptor (D/A) dyad shows a long‐lived triplet charge transfer ( 3 CT) state (0.94 μs) with a high energy level (ca. 2.12 eV), based on a new electron spin‐control method using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC) ( 1 NI*→ 1 CT→ 3 NI*→ 3 CT; NI=naphthalimide), without heavy atoms or chromophores with intrinsic intersystem crossing (ISC) ability.