INTRAMOLECULAR ASPECTS OF THE ELECTRON-TRANSFER IN THE BIFERROCENIUM MIXED-VALENCE CATION, USING PKS THEORY

The electron transfer properties of the mixed-valence biferrocenium cation are investigated using the Piepho-Krausz-Schatz (PKS) vibronic theory. Parameters of the model are deduced from both vibrational spectroscopy (stiffness constant) and MO calculations (transfer integral and vibronic coupling parameter); the computed asymmetric distortion agrees with structural data; a specific heat Schottky anomaly, recently reported, is also explained in the frame of that model. The low-temperature transfer rate is also computed. It ranges from 1.5 x 10(10) to 8.7 x 10(12) s-1, according to the nature of the HOMO, and definitively lies higher than the Mossbauer timescale (almost-equal-to 10(8) s-1).