Ultrafast TRIR and DFT Studies of the Photochemical Dynamics of Co-4(CO)(12) in Solution

作者：Lomont Justin P; Nguyen Son C; Harris Charles B^*

来源：Organometallics, 2012, 31(10): 4031-4038.

DOI：10.1021/om300262s

The photochemical rearrangement dynamics of Co-4(CO)(12) were studied using picosecond time-resolved infrared spectroscopy. In cyclohexane and CH2Cl2 solvents, monitoring the kinetics of absorptions in the bridging carbonyl region reveals the formation of two transient rearrangement intermediates, both of which revert to the parent complex on the picosecond time scale. Density functional theory calculations are used to identify the structures of the rearrangement products, which arise from cleavage of an apical-basal Co-Co bond. While the lifetimes of both species exhibit a solvent dependence, the experimental kinetics and density functional calculations suggest that these species do not form solvent-coordinated complexes with cyclohexane or CH2Cl2, and instead, the solvent effect is believed to arise from differences in polarity, with the more polar CH2Cl2 solvent stabilizing the rearrangement intermediates, relative to when cyclohexane is the solvent. Carbonyl dissociation products are also observed and investigated by DFT calculations. No fragmentation products, such as Co(CO)(4) or Co-2(CO)(5), are observed to form on the picosecond time scale, suggesting that subsequent chemistry of this cluster will occur via the single carbonyl-loss products. The experimental and computational results of this study provide insight into the role and nature of bridging carbonyl intermediates formed upon photoexcitation, as well as the formation of carbonyl-loss products and the role of solvation of transient species. To our knowledge, this study represents the first investigation into the dynamics of an M4L12 complex on the ultrafast time scale.

• 出版日期2012-5-28