Electronic interactions and energy transfer in oligothiophene-linked bis-porphyrins

The photophysical and spectroscopic properties of a series of bis-porphyrin compounds meso-meso-linked via oligothiophene bridges are reported. In particular the effects of the different bridges on the porphyrin properties as well as their ability to enhance energy transfer is investigated. The main findings are: a splitting of the degeneracy of the porphyrin Soret band transition with a lower energy transition aligned along the bridge, a dramatic decrease in triplet lifetime and the occurrence of "superexchange" as the main mechanism for mediating singlet-singlet energy transfer in the case where the bridge is a quaterthiophene. Our results show significant perturbations of the intrinsic porphyrin properties induced by the bridge, which are important for the function of porphyrin assemblies.