Multistep photoinduced electron transfer in a photoacceptor terminated molecular triode

A mol.ecular triode (I) containing a nonconjugatively interconnected array (D2-D1-Pa) of 2 potential 1-electron donor (D) moieties and a powerful photoacceptor (Pa), is described. In a related diode (II) consisting of the array D1-Pa excitation of the photoacceptor, Pa, induces charge-separation as detected by time-resolved microwave conductivity (TRMC) measurements and as evidenced from the observation of charge-transfer emission resulting from radiative recombination. The latter emission is quenched in the triode III indicating occurrence of virtually complete consecutive electron transfer from D2 to D1. Instead, III displays a much weaker charge transfer emission at longer wavelength attributed to direct radiative recombination from D2 to Pa. Fluorescence lifetime measurements and TRMC data show that the recombination in III is greatly slowed down as compared to the short-range recombination in II.