Resonance-enhanced charge delocalization in carbazole-oligoyne-oxadiazole conjugates

Zieleniewska, A; Zhao, X.; Bauroth, S.; Wang, C.; Batsanov, A.S.; Calderson, C.K.; Kahnt, A.; Clark, T.; Bryce, M.R.; Guldi, D.M.

Abstract

There are notably few literature reports of electron donor-acceptor oligoynes although they offer unique opportunities for studying charge transport through ‘all-carbon’ molecular bridges. In this context, the current study focuses on a series of carbazole–(C≡C)n-2,5-diphenyl-1,3,4-oxadiazoles (n = 1-4) as conjugated π-systems, in general, and explores their photophysical properties, in particular. Contrary to the behavior of typical electron donor-acceptor systems, for these oligoynes the rates of charge recombination after photoexcitation increase with increasing electron donoracceptor distance. To elucidate this unusual performance, detailed photophysical and time-dependent density functional theory investigations were conducted. Significant delocalization of the electron density along the bridge indicates that the bridging states come into resonance with either the electron donor or acceptor, thereby accelerating the charge transfer. Moreover, the calculated bond lengths reveal a reduction in bond length alternation upon photoexcitation, indicating significant cumulenic character of the bridge in the excited state. In short, strong vibronic coupling between the electrondonating N-arylcarbazoles and the electron-accepting 1,3,4-oxadiazoles accelerates the charge recombination as the oligoyne becomes longer.

Citation

Zieleniewska, A., Zhao, X., Bauroth, S., Wang, C., Batsanov, A., Calderson, C., Kahnt, A., Clark, T., Bryce, M., & Guldi, D. (2020). Resonance-enhanced charge delocalization in carbazole-oligoyne-oxadiazole conjugates. Journal of the American Chemical Society, 142(44), 18769-18781. https://doi.org/10.1021/jacs.0c04003

• Journal Article Type: Article
• Online Publication Date: Oct 21, 2020
• Publication Date: Nov 4, 2020
• Deposit Date: Oct 8, 2020
• Publicly Available Date: Oct 21, 2021
• Journal: Journal of the American Chemical Society
• Print ISSN: 0002-7863
• Electronic ISSN: 1520-5126
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 142
• Issue: 44
• Pages: 18769-18781
• DOI: https://doi.org/10.1021/jacs.0c04003
• Public URL: https://durham-repository.worktribe.com/output/1260561
• Publisher URL: https:/doi.org/10.1021/jacs.0c04003