Spectroscopic Investigation of Size-Dependent CO2 Binding on Cationic Copper Clusters: Analysis of the CO2 Asymmetric Stretch

Abstract

Photofragmentation spectroscopy, combined with quantum chemical computations, was employed to investigate the position of the asymmetric CO2 stretch in cold He-tagged Cun[CO2]+ (n = 1-10) and Cun[CO2][H2O]+ (n = 1-7) complexes. A blue shift in the band position was observed compared to the free CO2 molecule for Cun[CO2]+ complexes. Furthermore, this shift was found to exhibit a notable dependence on cluster size, progressively redshifting with increasing cluster size. The computations revealed that the CO2 binding energy is the highest for the Cu+ and continuously decreases with increasing cluster size. This dependency could be explained by highlighting the role of polarization in electronic structure, according to energy decomposition analysis. Introduction of water to this complex amplified the redshift of the asymmetric stretch, showing a similar dependency on the cluster size as observed for Cun[CO2]+ complexes.