Electronic Spectroscopy and Photodissociation Dynamics of Hydrated Co2+Clusters: Co2+(H2O)n(n= 4−7)

Abstract

Solvated cluster ions Co2+(H2O)n with n = 4−7 have been generated by electrospray ionization and studied by laser photofragment spectroscopy. The similarity between the spectrum of gas-phase Co2+(H2O)6 and the absorption spectrum of aqueous cobalt(II) suggests that Co2+(H2O)6 (aq) is responsible for the room-temperature solution absorption spectrum. The observed photodissociation spectrum of Co2+(H2O)4 is similar to new bands which appear in aqueous cobalt(II) at high temperatures and have been assigned to Co2+(H2O)4 (aq) by Swaddle and Fabes (Swaddle, T. W.; Fabes, L. Can. J. Chem. 1980, 58, 1418−1426). The hexahydrate was found to dissociate by loss of one or two water molecules, whereas the heptahydrate dissociates by loss of two or three water molecules. In both cases, loss of two water molecules is the preferred dissociation pathway. The tetrahydrate dissociates either by simple loss of water or by charge separation to form CoOH+(H2O)2 and H3O+, with charge separation being the preferred dissociation...