Near-UV Water Splitting by Cu, Ni, and Co Complexes in the Gas Phase

(2,2'-Bipyridine)M═O⁺ ions (M = Cu, Ni, Co) were generated by collision-induced dissociation and near-UV photodissociation of readily available [(2,2'-bipyridine)M^II(NO₃)]⁺ ions in the gas phase, and their structure was confirmed by ion-molecule reactions combined with isotope labeling. Upon storage in a quadrupole ion trap, the (2,2'-bipyridine)M═O⁺ ions spontaneously added water, and the formed [(2,2'-bipyridine)M═O + H₂O]⁺ complexes eliminated OH upon further near-UV photodissociation. This reaction sequence can be accomplished at a single laser wavelength in the range of 260-340 nm to achieve stoichiometric homolytic cleavage of gaseous water. Structures, spin states, and electronic excitations of the metal complexes were characterized by ion-molecule reactions using ²H and ¹⁸O labeling, photodissociation action spectroscopy, and density functional theory calculations.