EVIDENCE FOR PARALLEL PHOTOINDUCED ELECTRON-TRANSFER IN DIQUINONE SUBSTITUTED PORPHYRINS

Fluorescence spectra and decay kinetics of diquinone substituted porphyrins were examined in a comparison with those of monoquinone substituted porphyrins. Fluorescence quenching of the diquinone molecules is larger than that of the monoquinones and the electron-transfer rate constants of the diquinones are larger than those of the monoquinones by a factor of two regardless of the rigidity of the spacer groups indicating the existence of the parallel electron-transfer mechanism in diquinones.