, 133:1450
Date: 07 Feb 2014

Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters

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Abstract

We examine theoretically the three channels that are associated with the detachment of a single water molecule from the aqueous clusters of the alkaline earth dications, [M(H2O) n ]2+, M = Mg, Ca, Sr, Ba, n ≤ 6. These are the unimolecular water loss (M2+(H2O) n−1 + H2O) and the two hydrolysis channels resulting the loss of hydronium ([MOH(H2O) n−2]+ + H3O+) and Zundel ([MOH(H2O) n−3]+ + H3O+(H2O)) cations. Minimum energy paths (MEPs) corresponding to those three channels were constructed at the Møller–Plesset second order perturbation (MP2) level of theory with basis sets of double- and triple-ζ quality. We furthermore investigated the water and hydronium loss channels from the mono-hydroxide water clusters with up to four water molecules, [MOH(H2O) n ]+, 1 ≤ n ≤ 4. Our results indicate the preference of the hydronium loss and possibly the Zundel-cation loss channels for the smallest size clusters, whereas the unimolecular water loss channel is preferred for the larger ones as well as the mono-hydroxide clusters. Although the charge separation (hydronium and Zundel-cation loss) channels produce more stable products when compared to the ones for the unimolecular water loss, they also require the surmounting of high-energy barriers, a fact that makes the experimental observation of fragments related to these hydrolysis channels difficult.

Dedicated to Professor Thom Dunning and published as part of the special collection of articles celebrating his career upon his retirement.