Charge Separation and Intersystem Crossing in Homo- and Hetero-Compact Naphthalimide Dimers
| Autor: | Wen Tian, Andrey A. Sukhanov, Laura Bussotti, Junhong Pang, Jianzhang Zhao, Violeta K. Voronkova, Mariangela Di Donato, Ming-De Li |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | The journal of physical chemistry. B 126 (2022): 4364–4378. doi:10.1021/acs.jpcb.2c02276 info:cnr-pdr/source/autori:Tian W.; Sukhanov A.A.; Bussotti L.; Pang J.; Zhao J.; Voronkova V.K.; Di Donato M.; Li M.-D./titolo:Charge Separation and Intersystem Crossing in Homo-and Hetero-Compact Naphthalimide Dimers/doi:10.1021%2Facs.jpcb.2c02276/rivista:The journal of physical chemistry. B/anno:2022/pagina_da:4364/pagina_a:4378/intervallo_pagine:4364–4378/volume:126 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/acs.jpcb.2c02276 |
| Popis: | Naphthalimide (NI) homo- and hetero-dimers adopting orthogonal geometry were prepared to study photo-induced symmetry-breaking charge transfer (SBCT) and charge recombination (CR)-induced intersystem crossing (ISC). The two moieties in the dimer are connected either at the 3-C or 4-C position of the NI unit. The photophysical properties of the dimers were studied with steady-state and transient absorption spectroscopic methods. Significant CT only occurs for the hetero-dimer, in which one NI unit has a 4-amino substituent and the other NI unit is without it. The CR-induced ISC is most efficient for this dimer (singlet oxygen quantum yield ?= 50.3%). For the homo-dimer, in which both NI units did not present amino substitution, SBCT was not observed. Based on the electrochemical studies, we propose that the absence of SBCT for the homo-dimer is attributed to its high oxidation potential and low reduction potential. Femtosecond transient absorption (fs TA) spectra show that there is no charge separation (CS) for the homo-dimer. Nanosecond transient absorption spectroscopy indicate the formation of a triplet state with electron delocalization for the homo dimer, with a lifetime of 72.0 ?s, while for the hetero dimer a triplet state with an intrinsic lifetime of 206.4 ?s is observed. CS (11.6 ps) and slow CR-induced ISC (>1.5 ns) were observed for the hetero-dimer. Time-resolved electron paramagnetic resonance spectra give the zero-field splitting parameters (|D| = 1894 MHz and |E| = 111 MHz) and electron spin polarization patterns (e, e, e, a, a, a) for the triplet state of the hetero-dimer, inferring that the triplet state of the hetero-dimer is confined on the amino-substituted NI moiety. |
| Databáze: | OpenAIRE |
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