Ultrafast electron transfer and coupled vibrational dynamics in cyanide bridged mixed-valence transition-metal dimers

Picosecond infrared spectroscopy has been used to investigate electron transfer and vibrational excitation and relaxation in the mixed-valence transition-metal dimer [(NC)[sub 5]M[sup II]CNM[sup III](NH[sub 3])[sub 5]][sup [minus]](M = Ru, Os). Optical excitation into the metal-to-metal charge transfer band results in formation of the excited state redox isomer [(NC)[sub 5]M[sup III]CNM[sup II](NH[sub 3])[sub 5]][sup [minus]]. Subsequent back electron transfer results in reformation of the ground state and occurs with [tau] < 0.5 ps. Upon return to the ground electronic state, large amounts of energy (up to 7 quanta, 14 000 cm[sup [minus]1]) are placed into the terminal MC[triple bond]N stretching mode. The rate of the subsequent energy relaxation was measured; decay times ranged from