ELECTRON AND ENERGY-TRANSFER PROCESSES OF PHOTOEXCITED OLIGOTHIOPHENES ONTO TETRACYANOETHYLENE AND C-60

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). © 1994 American Institute of Physics.