title: Structural rearrangements and magic numbers in reactions between pyridine-containing water clusters and ammonia.
abstract: Molecular cluster ions H(+)(H(2)O)(n), H(+)(pyridine)(H(2)O)(n), H(+)(pyridine)(2)(H(2)O)(n), and H(+)(NH(3))(pyridine)(H(2)O)(n) (n = 16-27) and their reactions with ammonia have been studied experimentally using a quadrupole-time-of-flight mass spectrometer. Abundance spectra, evaporation spectra, and reaction branching ratios display magic numbers for H(+)(NH(3))(pyridine)(H(2)O)(n) and H(+)(NH(3))(pyridine)(2)(H(2)O)(n) at n = 18, 20, and 27. The reactions between H(+)(pyridine)(m)(H(2)O)(n) and ammonia all seem to involve intracluster proton transfer to ammonia, thus giving clusters of high stability as evident from the loss of several water molecules from the reacting cluster. The pattern of the observed magic numbers suggest that H(+)(NH(3))(pyridine)(H(2)O)(n) have structures consisting of a NH(4)(+)(H(2)O)(n) core with the pyridine molecule hydrogen-bonded to the surface of the core. This is consistent with the results of high-level ab initio calculations of small protonated pyridine/ammonia/water clusters.
authors.affiliation: Mass Spectrometry Laboratory and Centre of Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, NO-0315 Oslo, Norway. mauritz.ryding@kjemi.uio.no
authors.forename: Mauritz J
authors.initials: MJ
authors.lastname: Ryding
authors.forename: Kai
authors.initials: K
authors.lastname: Ruusuvuori
authors.forename: Patrik U
authors.initials: PU
authors.lastname: Andersson
authors.forename: Alexey S
authors.initials: AS
authors.lastname: Zatula
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: McGrath
authors.forename: Theo
authors.initials: T
authors.lastname: Kurtén
authors.forename: Ismael K
authors.initials: IK
authors.lastname: Ortega
authors.forename: Hanna
authors.initials: H
authors.lastname: Vehkamäki
authors.forename: Einar
authors.initials: E
authors.lastname: Uggerud
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D014867:Water / Q000737:chemistry*
chemical_list: D011725:Pyridines; D014867:Water; D000641:Ammonia; C023666:pyridine