title: Effect of alkali metal coordination on gas-phase chemistry of the diphosphate ion: the MH(2)P(2)O(7) (-) ions.
abstract: Systematic experimental and theoretical studies on anionic phosphate species in the gas phase are almost nonexistent, even though they could provide a benchmark for enhanced comprehension of their liquid-phase chemical behavior. Gaseous MH(2)P(2)O(7) (-) ions (M=Li, Na, K, Rb, Cs), obtained from electrospray ionization of solutions containing H(4)P(2)O(7) and MOH or M salts as a source of M(+) ions were structurally assayed by collisionally activated dissociation (CAD) mass spectrometry and theoretical calculations at the B3LYP/6-31+G* level of theory. The joint application of mass spectrometric techniques and theoretical methods allowed the MH(2)P(2)O(7) (-) ions to be identified as having a structure in which the linear diphosphate anion is coordinated to the M(+) ion (I) and provides information on gas-phase isomerization processes in the [PO(3)...MH(2)PO(4)](-) clusters II and the [P(2)O(6)...M...H(2)O](-) clusters IV. Studies of gas-phase reactivity by Fourier transform ion cyclotron resonance (FTICR) and triple quadrupole (TQ) mass spectrometry revealed that the MH(2)P(2)O(7) (-) ions react with selected nucleophiles by clustering, proton transfer and addition-elimination mechanisms. The influence of the coordination of alkali metal ions on the chemical behavior of pyrophosphate is discussed.
authors.affiliation: Dip.to di Studi di Chimica e Tecnologia delle Sostanze, Biologicamente Attive, Università di Roma "La Sapienza", P. le A. Moro 5, 00185 Rome, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Pepi
authors.forename: Andreina
authors.initials: A
authors.lastname: Ricci
authors.forename: Marzio
authors.initials: M
authors.lastname: Rosi
authors.forename: Marco
authors.initials: M
authors.lastname: Di Stefano