Probing charge separation in structurally different C-60/exTTF ensembles

Diaz, M.C.; Herranz, M.A.; Illescas, B.M.; Martin, N.; Godbert, N.; Bryce, M.R.; Luo, C.P.; Swartz, A.; Anderson, G.; Guldi, D.M.

Abstract

The scope of the present work is to highlight the effects stemming from different C-60/exTTF linkages (exTTF = 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene)-either via an anthracene unit or a dithiole ring. Particular emphasis is placed on photoinduced electron-transfer features. Therefore, we devised a new series Of C-60-exTTF ensembles, synthesized via 1,3-dipolar cycloaddition. and Diels-Alder cycloaddition reactions, in which exTTF units are separated from C-60 by two single bonds (3a-c, 4), one vinylene unit (5a), or two vinylene units (5b). The cyclic voltammetry reveals an amphoteric redox behavior with remarkably strong electron-donor ability of the trimethyl-substituted exTTF moiety in 4 and 5a,b. Steady-state and time-resolved photolytic techniques show that the fullerene singlet excited state in (3a-c, 4, and 5a,b) is subject to a rapid electron-transfer quenching. The resulting charge-separated states, that is C-60(.-)-exTTF(.+), were identified by transient absorption spectroscopy. We determined radical pair lifetimes of the order of 200 ns in benzonitrile. This suggests (i) that the positive charge of the exTTF(.+) is delocalized over the entire donor rather than localized on one of the 1,3-dithiole rings and (ii) that linking exTTF via the anthracene or 1,3-dithiole ring has no appreciable influence. Increasing the donor-acceptor separation via implementing one or two vinylene units as spacers led to improved radical pair lifetimes (5a: tau = 725 ns; 5b: tau = 1465 ns).

Citation

Diaz, M., Herranz, M., Illescas, B., Martin, N., Godbert, N., Bryce, M., …Guldi, D. (2003). Probing charge separation in structurally different C-60/exTTF ensembles. Journal of Organic Chemistry, 68(20), 7711-7721

• Journal Article Type: Article
• Publication Date: 2003-10
• Journal: Journal of Organic Chemistry
• Print ISSN: 0022-3263
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 68
• Issue: 20
• Pages: 7711-7721