Direct Experimental Comparison of the Theories of Thermal and Optical Electron-Transfer: Studies of a Mixed-Valence Dinuclear Iron Polypyridyl Complex

Abstract

The spectral parameters for the optically induced intervalence charge transfer and the rates of thermal electron transfer as a function of temperature have been measured for a rigid, triply linked mixed-valence dinuclear tris(2,2‘-bipyridine)iron complex. The total reorganizational energy associated with the intramolecular electron exchange in this complex is almost exclusively outer-sphere in nature and comes from thermal fluctuations of the solvent. Thus, the system can be treated rigorously at the classical level, where in this context classical refers to treatments of the nuclear modes. The theories developed to describe the optical electron transfer and the thermal electron transfer are evaluated by analysis of the spectral and rate data, respectively. The quantities common to both theories are the donor−acceptor coupling matrix element, H12, and the total reorganizational energy. Applying the respective theories to the appropriate corresponding sets of data yields reorganizational energies that are ...