Structures and Infrared Spectra of [M(CO2)7]+ (M = V, Cr, and Mn) Complexes.

Gas-phase infrared photodissociation spectra of [V(CO2) n]+ complexes revealed three new vibrational bands at 1140, 1800, and 3008 cm-1 at n = 7, the features of which are retained in the larger clusters (Ricks, A. M.; Brathwaite, A. D.; Duncan, M. A. J. Phys. Chem. A 2013, 117, 11490-11498). However, structural assignment of this intriguing feature remains open. Herein, quantum chemical calculations on [V(CO2)7]+ were carried out to identify the structure of the low-lying isomers and to assign the observed spectral features. The comparison of calculated infrared spectra of [V(CO2)7]+ with experimental infrared spectra identified the formation of a bent CO2- species, suggesting the ligand-induced activation of CO2 by the vanadium cation. The structures and infrared spectra of [Cr(CO2)7]+ and [Mn(CO2)7]+ were also predicted and discussed.