Electrospray Ionization Based Methods for the Generation of Polynuclear Oxo- and Hydroxo Group 6 Anions in the Gas-Phase

Electrospray ionization (ESI) of the Lindqvist (n-Bu4N)(2)[M6O19] (M = Mo, W) polyoxometalates provides a straightforward entry for the generation of an assortment of oxo- and hydroxo anions in the gas-phase. In particular, the series of oxo dianions of general formula [(MO3) (n) O](2-) (n = 2-6; M = Mo, W), monoanions, namely [(MO3) (n) O](-) (n = 1, 2) and [(MO3) (n) ](-) (n = 1, 2), and the hydroxo [(MO3) (n) (OH)](-) (n = 1-6) species can be readily generated in the gas-phase upon varying the solvent composition as well as the ionisation conditions (typically the U-c cone voltage). Complementary tandem mass experiments (collision induced dissociation and ion-molecule reactions) are also used aimed to investigate the consecutive dissociation of these species and their intrinsic gas-phase reactivity towards methanol. Special emphasis is paid to some of the key factors of these group 6 anions related to the gas-phase activation of methanol, such as molecular composition, open vs closed shell electronic nature and cluster size.