ELECTRONIC COUPLING IN OBLIQUE BISPORPHYRINS

Rates of photoinduced electron transfer were measured for a bisporphyr in, comprised of gold(III) and zinc(II) porphyrinic subunits separated by a 2,9-diphenyl-1,10-phenanthroline spacer, in butyronitrile at var ious temperatures, solvents of differing polarity at ambient temperatu re, and frozen ethanol. Corresponding data were collected for rotaxane s formed by coordination of the phenanthroline to a metal complex and ring closure. Treating the data according to nonadiabatic electron tra nsfer theory provides values for the extent of electronic coupling bet ween porphyrins, total reorganization energy, and rate of electron tra nsfer at zero activation free energy. These parameters are discussed i n terms of the molecular architecture.