Electronic and Vibrational Spectroscopy and Vibrationally Mediated Photodissociation of V+(OCO)

Electronic spectra of gas-phase V+(OCO) are measured in the near-infrared from 6050 to 7420 cm-1 and in the visible from 15 500 to 16 560 cm-1, using photofragment spectroscopy. The near-IR band is complex, with a 107 cm-1 progression in the metal−ligand stretch. The visible band shows clearly resolved vibrational progressions in the metal−ligand stretch and rock, and in the OCO bend, as observed by Brucat and co-workers. A vibrational hot band gives the metal−ligand stretch frequency in the ground electronic state ν3‘ ‘ = 210 cm-1. The OCO antisymmetric stretch frequency in the ground electronic state (ν1‘ ‘) is measured by using vibrationally mediated photodissociation. An IR laser vibrationally excites ions to ν1‘ ‘ = 1. Vibrationally excited ions selectively dissociate following absorption of a second, visible photon at the ν1‘ = 1 ← ν1‘ ‘ = 1 transition. Rotational structure in the resulting vibrational action spectrum confirms that V+(OCO) is linear and gives ν1‘ ‘ = 2392.0 cm-1. The OCO antisymmetric stretch frequency in the excited electronic state is ν1‘ = 2368 cm-1. Both show a blue shift from the value in free CO2, due to interaction with the metal. Larger blue shifts observed for complexes with fewer ligands agree with trends seen for larger V+(OCO) n clusters.