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.

Proton affinities of candidates for positively charged ambient ions in boreal forests

“…The exact details of this evaluation can be found in the original article, but the basic idea was to use computational PAs as well as experimental data in determining a suitable PA scale and then adjust experimental and relative PA values based on this scale. Since the computational values used to determine the PA scale play a key role in this kind of an evaluation, it should be noted that the computational values used by Hunter and Lias were calculated with a slightly modified G2 method (Smith and Radom, 1993). Based on our benchmarking calculations, the standard G2 method is comparable in accuracy with the CBS-QB3 method, so the good general agreement with the evaluated results and CBS-QB3 results is not surprising.…”

“…The B3LYP/6-31++G(2df,2dp)//RI-MP2-F12/cc-pVDZ-F12 method comprised of geometries and thermodynamic corrections calculated with Gaussian 09 at the B3LYP/6-31++G(2df,2dp) level and electronic energies calculated with Turbomole 6.3 (Ahlrichs et al, 1989, Turbomole 6.3, Turbomole GmbH) at the RI-MP2-F12/cc-pVDZ-F12 level. A more detailed description of the method as well as all the relevant references can be found in Ryding et al (2012).…”

Computational study of the Rayleigh light scattering properties of atmospheric pre-nucleation clusters

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CO2incorporation in hydroxide and hydroperoxide containing water clusters—a unifying mechanism for hydrolysis and protolysis

“…The experiments were performed using a quadrupole-time-of-flight mass spectrometer (QTOF2, Micromass/Waters, Manchester UK), as previously used by us. [45][46][47][48][49][50] The instrument has been modified to allow for volatile and semi-volatile gases to be injected into the instrument's collision-cell via a stainless steel inlet system.…”