Photoinduced Charge Shifts and Electron Transfer in Viologen-Tetraphenylborate Complexes: Push-Pull Character of the Exciplex

Autor(es)

Santos, Willy G. ; Budkina, Darya S. ; Deflon, Victor M. ; Tarnovsky, Alexander N. ; Cardoso, Daniel R. ; Forbes, Malcolm D. E.

• Tipo de documento: Artigo Científico
• Fonte: Journal of the American Chemical Society; v. 139, n. 23, p. 7681-7684, JUN 14 2017.
• Citações Web of Science: 16

Resumo

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 (k(obs) < 10(12) s(-1)) and twisted (k(obs) 10(10) 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 mu s 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 center dot+). (AU)

• Processo FAPESP: 15/13756-1 - Fotoquimica e dinamica de estados excitados de tetraarilboratos e complexos de tetraarilborato-piridinium.
• Beneficiário: Willy Glen Santos
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Processo FAPESP: 12/19823-4 - Fototransientes de organoboranos gerados por fotólise direta e sensitização por flavinas.
• Beneficiário: Willy Glen Santos
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado