Ultrafast Infrared Spectroscopy of Vibrational States Prepared by Photoinduced Electron Transfer in (CN)5FeCNRu(NH3)5-

Abstract

The picosecond time-resolved infrared spectra of (CN)5FeCNRu(NH3)5- were collected following optical excitation and reverse electron transfer. The measured reverse electron transfer rates are greater than 3 × 1012 s-1. In both formamide and deuterated water solutions, vibrational excitation in CN stretch modes is found after reverse electron transfer. The transient spectra at both earlier (1−35 ps) and later (10 ns) times give evidence of environment−solute coupling that can be accounted for by solvent heating and ion pair dynamics. A simulation of the spectral dynamics in formamide solution is presented using a kinetic model for vibrational excitation and relaxation. The simulation includes minor excitation in vibrational modes consistent with resonance Raman derived Franck−Condon factors, but it is also found that a nontotally symmetric mode is equally important as an acceptor.