Multicomponent Cluster Ions. 2. Comparative Stabilities of Cationic and Anionic Hydrogen-Bonded Networks. Mixed Clusters of Water and Hydrogen Cyanide

Article abstract of DOI:10.1021/j100346a058

The thermocemistry of cluster ions containing nH2O and mHCN molecules,for cluster up to rank r = n + m = 5, was obtained from equilibrium measurements.The clustering of H2O about H3O+ and OH- and the clustering of HCN about HCNH+ show distinct shell filling effects, but the clustering of H2O and HCN about CN- does not.Hydratation by one water molecule eliminates the difference of 5 kcal/mol between the proton affinities of HCN and H2O.Hydration also decreases the difference between the intrinsinc deprotonation energies, i.e., ΔH⁰_acid, of H2O and HCN from 37.7 to 19.8 kcal/mol in the 4-fold hydrated species.In protonated clusters of a given rank r, exchange of H2O by HCN does not significantly affect the total stability of the cluster.This is in contrast to H2O/CH3OH and H2O/CH3CN protonated clusters and H2O/HCN anionic clusters, where increasing nonaqueous content is stabilizing.In the latter, the most stable clusters of any size are the neat CN-.nHCN clusters.