Photoinduced electron transfer between 1,2,5-triphenylpyrrolidinofullerene cluster aggregates and electron donors

Abstract

Fullerene derivative 1,2,5-triphenylpyrrolidinofullerene (TPPF) forms optically transparent clusters (mean diameter of ~180 nm) in toluene/acetonitrile mixtures. The bimolecular rate constants for the quenching of a singlet excited state of TPPF clusters by various electron donors (substituted anilines and heteroaromatics) were found to be significantly higher than that of the corresponding monomeric analogue. The local concentration of the fullerene molecules is much higher in these clusters because the microheterogeneous environment facilitates trapping of donor molecules. Formation of long-lived electron-transfer products, following the photoexcitation of the TPPF cluster and various electron donors, was confirmed through flash photolysis studies. The TPPF cluster-donor assemblies when deposited as a thin film on a nanostructured SnO₂ semiconductor film, act as a photosensitive electrode material. Light energy can be harvested using an intermolecular electron transfer between the TPPF cluster film and the corresponding electron donor in a photoelectrochemical cell. Photocurrents of up to 0.4 μA/cm² have been achieved in the TPPF-N-methylphenothiazine cluster system under visible light irradiation.