VIBRATIONAL-ENERGY REDISTRIBUTION IN CP-ASTERISK-IR(CO)2 (CP-ASTERISK=ETA(5)-PENTAMETHYLCYCLOPENTADIENYL) STUDIED BY BROAD-BAND TRANSIENT INFRARED-SPECTROSCOPY

Picosecond vibrational energy dynamics involving the symmetric (2020 cm-1) and asymmetric (1953 cm-1) CO-stretching modes of Cp*Ir(CO)2 in room temperature n-hexane is measured using mode specific infrared excitation followed by broadband infrared multichannel probing to generate a transient spectrum. The recovery of the transient bleaching and absorption bands, following 2020 or 1953 cm-1 excitation, yields a upsilon = 1 CO-stretching lifetime T1 = 28 +/- 7 (1sigma) ps. The transitions from upsilon = 7 vibrational states give rise to new absorption features in the transient spectra at 2008, 1994, 1941 and 1930 cm-1. The time evolution of these absorption monitors rapid energy redistribution and equilibration (< 10 ps) between the symmetric and asymmetric CO-stretching modes prior to ground state recovery.