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

Author(s)

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

• Document type: Journal article
• Source: Journal of the American Chemical Society; v. 139, n. 23, p. 7681-7684, JUN 14 2017.
• Web of Science Citations: 16

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 (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)

• FAPESP's process: 15/13756-1 - Photochemistry and Excited-states Dynamics of Tetraarylborates and Tetraarylborate-pyridinium complexes.
• Grantee: Willy Glen Santos
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 12/19823-4 - Phototransients of organoboranes generated by photolysis and Flavin sensitization.
• Grantee: Willy Glen Santos
• Support Opportunities: Scholarships in Brazil - Post-Doctoral