1. Photoinduced Charge Shifts and Electron Transfer in Viologen-Tetraphenylborate Complexes: Push-Pull Character of the Exciplex
- Author
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Victor M. Deflon, Alexander N. Tarnovsky, Malcolm D. E. Forbes, Willy G. Santos, Daniel R. Cardoso, and Darya S. Budkina
- Subjects
Tetraphenylborate ,010405 organic chemistry ,ESPECTROSCOPIA MOLECULAR ,Viologen ,Electron donor ,General Chemistry ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,Photoinduced electron transfer ,0104 chemical sciences ,Dication ,chemistry.chemical_compound ,Electron transfer ,Colloid and Surface Chemistry ,chemistry ,Ultrafast laser spectroscopy ,medicine ,Triplet state ,medicine.drug - Abstract
Viologen–tetraarylborate ion-pair complexes were prepared and investigated by steady-state and time-resolved spectroscopic techniques such as fluorescence and femtosecond transient absorption. The results highlight a charge transfer transition that leads to changes in the viologen structure in the excited singlet state. Femtosecond transient absorption reveals the formation of excited-state absorption and stimulated emission bands assigned to the planar (kobs < 1012 s–1) and twisted (kobs ∼ 1010 s–1) structures between two pyridinium groups in the viologen ion. An efficient photoinduced electron transfer from the tetraphenylborate anionic moiety to the viologen dication was observed less than 1 μs after excitation. This is a consequence of the push–pull character of the electron donor twisted viologen structure, which helps formation of the borate triplet state. The borate triplet state is deactivated further via a second electron transfer process, generating viologen cation radical (V•+).
- Published
- 2017