Photoinduced Intramolecular Electron-Transfer Processes in [60]Fullerene and N,N-Bis(biphenyl)aniline Molecular Systems in Solutions

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2005-09, Vol.109 (36), p.8088-8095
• Main Authors: Sandanayaka, Atula S. D, Ikeshita, Kei-ichiro, Rajkumar, G. Abraham, Furusho, Yoshio, Araki, Yasuyuki, Takata, Toshikazu, Ito, Osamu
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp052063f

Photoinduced intramolecular charge-separation and charge-recombination processes in covalently connected C60 -(spacer)-bis(biphenyl)aniline (C60-sp-BBA) and C60-((spacer)-bis(biphenyl)aniline)2 (C60-(sp-BBA)2) have been studied by time-resolved fluorescence and transient absorption methods. Since a flexible alkylthioacetoamide chain was employed as the spacer, the folded structures in which the BBA moiety approaches the C60 moiety were obtained as optimized structures by molecular orbital calculations. The observed low fluorescence intensity and the short fluorescence lifetime of the C60 moiety of these molecular systems indicated that charge separation takes place via the excited singlet state of the C60 moiety in a quite fast rate and high efficiency even in the nonpolar solvent toluene, which was a quite new observation compared with reported dyads with different spacers. From the absorption bands at 880 and 1000 nm in the nanosecond transient absorption spectra, generations of C60 •--sp-BBA•+ and C60 •--(sp-BBA•+)(sp-BBA) were confirmed. The rates of charge separation and charge recombination for C60-(sp-BBA)2 are faster than those for C60-sp-BBA, suggesting that one of the BBA moieties approaches the C60 moiety by pushing another BBA moiety because of the flexible spacers.