Photochemistry of charge-transfer complexes in a viologen periodic mesoporous organosilica: Time evolution from femtoseconds to minutes

Abstract

Persistent radical cations can be generated in V∝PMO, a periodic mesoporous organosilica incorporating a viologen in its silicate framework. Photoexcitation of V∝PMO forms a geminate viologen–halide ion pair that can undergo rapid charge recombination or electron hopping to form the nongeminate ion pair, which persists for minutes (see picture). In contrast, viologen–halide CT complexes in solution undergo complete charge recombination on the sub-nanosecond timescale.