Gaseous MH2P2O7- ions (M= Li, Na, K, Rb, Cs) obtained from Electrospray Ionization of solutions containing H4P2O7 and MOH or M salts as a source of the M+ cations, are structurally assayed by collisionally activated dissociation (CAD) mass spectrometry and by theoretical calculations performed at the B3LYP/6-31+G* level of theory. Theoretical calculations allow the origin of the CAD fragments to be identified and the ionic population of MH2P2O7- ions to be characterized essentially as the linear diphosphate anion coordinated to the M+ cation. Minor amounts of the [PO3•••M•••PO3•••H2O]– clusters are also present when M is Li, Na and K. The joint application of mass spectrometric techniques and theoretical methods provide information on the dissociative processes of MH2P2O7- ions in the gas phase. The isomerization of the MH2P2O7- ion into the [PO3•••MH2PO4]- cluster, involving an intramolecular proton shift to the bridging oxygen, is computed endothermic by 12,6 kcal/mol and having an energy barrier of 29.1 kcal mol-1 for M=Li. The endothermic of the process drops to 5,2 kcal mol-1 with a barrier height of 20,4 kcal mol-1 for M= Na. The structures and the stabilities of the [P2O6 •••M•••H2O]- and [PO3 • • •M • • PO3 • • H2O]- clusters are also reported. The previously unexplored gas phase reactivity of MH2P2O7- ions is investigated by FTICR and TQ mass spectrometry.
Effect of alkali metal coordination on gas-phase chemistry of the diphosphate ion: the MH2P2O7- ions
ROSI, Marzio;
2006
Abstract
Gaseous MH2P2O7- ions (M= Li, Na, K, Rb, Cs) obtained from Electrospray Ionization of solutions containing H4P2O7 and MOH or M salts as a source of the M+ cations, are structurally assayed by collisionally activated dissociation (CAD) mass spectrometry and by theoretical calculations performed at the B3LYP/6-31+G* level of theory. Theoretical calculations allow the origin of the CAD fragments to be identified and the ionic population of MH2P2O7- ions to be characterized essentially as the linear diphosphate anion coordinated to the M+ cation. Minor amounts of the [PO3•••M•••PO3•••H2O]– clusters are also present when M is Li, Na and K. The joint application of mass spectrometric techniques and theoretical methods provide information on the dissociative processes of MH2P2O7- ions in the gas phase. The isomerization of the MH2P2O7- ion into the [PO3•••MH2PO4]- cluster, involving an intramolecular proton shift to the bridging oxygen, is computed endothermic by 12,6 kcal/mol and having an energy barrier of 29.1 kcal mol-1 for M=Li. The endothermic of the process drops to 5,2 kcal mol-1 with a barrier height of 20,4 kcal mol-1 for M= Na. The structures and the stabilities of the [P2O6 •••M•••H2O]- and [PO3 • • •M • • PO3 • • H2O]- clusters are also reported. The previously unexplored gas phase reactivity of MH2P2O7- ions is investigated by FTICR and TQ mass spectrometry.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
