Proton mobility and stability of water clusters containing the bisulfate anion, HSO4−(H2O)n

Abstract

Bisulfate water clusters, HSO(4)(-)(H(2)O)(n), have been studied both experimentally by a quadrupole time-of-flight mass spectrometer and by quantum chemical calculations. For the cluster distributions studied, there are some possible "magic number" peaks, although the increase in abundance compared to their neighbours is small. Experiments with size-selected clusters with n = 0-25, reacting with D(2)O at a center-of-mass energy of 0.1 eV, were performed, and it was observed that the rate of hydrogen/deuterium exchange is lower for the smallest clusters (n < 8) than for the larger (n > 11), with a transition taking place in the range n = 8-11. We propose that the protonic defect of the bisulfate ion remains rather stationary unless the degree of hydration reaches a given level. In addition, it was observed that H/D scrambling becomes close to statistically randomized for the larger clusters. Insight into this size dependency was obtained by B3LYP/6-311++G(2d,2p) calculations for HSO(4)(-)(H(2)O)(n) with n = 0-10. In agreement with experimental observations, these calculations suggest pronounced effectiveness of a ''see-saw mechanism'' for pendular proton transfer with increasing HSO(4)(-)(H(2)O)(n) cluster size.

Electron-induced chemistry in microhydrated sulfuric acid clusters

“…We used previously observed energetic minima from literature as the initial structures (Zatula et al, 2011;Husar et al, 2012;Temelso et al, 2012a, b;Henschel et al, 2014) and equilibrated them in molecular dynamics runs to find the most stable isomers. Molecular dynamics were run on the BLYP/6-31+g* potential energy surface, and nuclei were propagated according to classical equations of motion; the constant temperature of 298 K was maintained with a Nosé-Hoover thermostat.…”

“…However, the ion-induced nucleation alone could not explain the observed nucleation rates (Kirkby et al, 2011). Therefore, other compounds, such as bases (e.g., ammonia and amines) and organic acids, were proposed to contribute to the sulfuric acid aerosol formation (Zhang et al, 2004(Zhang et al, , 2012Kirkby et al, 2011;Almeida et al, 2013;Kürten et al, 2014Kürten et al, , 2016Schobesberger et al, 2015).…”

Mass spectrometry of aerosol particle analogues in molecular beam experiments

“…The (HNO 3 ) 1‐2 cluster ions are also converted to in reactions with H 2 SO 4 . Active proton transfer was observed even for the hydrated bisulfate anion on water clusters . Sulfuric acid molecules form very stable clusters with bisulfate anion bonded via strong triply hydrogen bond, which was proposed theoretically .…”

“…192 Active proton transfer was observed even for the hydrated bisulfate anion on water clusters. 194 Sulfuric acid molecules form very stable clusters with bisulfate anion bonded via strong triply hydrogen bond, which was proposed theoretically. 195,196 The structure of these cluster anions was confirmed by vibrational spectroscopy.…”

Nucleophilic Substitution in Reactions between Partially Hydrated Superoxide Anions and Alkyl Halides

“…63 For convenience, Table 1 shows the energy levels of the S N 2 reaction products (reaction 4) relative to the energy levels of the reactants, i.e., the data in Figure 4. First, the reaction exothermicity for the S N 2 reaction (reaction 4) decreases significantly with increasing cluster size, apparently an effect of the stronger hydration of the ionic O 2…”