Electron and energy transfer processes of photoexcited oligothiophenes onto tetracyanoethylene and C60

Abstract

We present near‐steady‐state photoinduced absorption (PIA) studies on photoexcited states of a series of oligothiophenes (nT, n=6,7,9,11) in solution. Photoexcitation in solution reveals efficient formation of a metastable triplet state (³nT). In addition, oligothiophene radical cations (nT^+.) are formed from the singlet excited state via electron transfer to the medium in solvents of high electron affinity. The reactivity of the ³nT state towards acceptor molecules is investigated. In the presence of C₆₀ an energy transfer reaction is observed which quenches the ³nT state and produces ³C₆₀ via photosensitization. Addition of tetracyanoethylene (TCNE) results in quenching of the ³nT state via electron transfer and efficiently produces the corresponding nT^+. radical cations, as evidenced from PIA and light‐induced electron spin resonance (ESR).