Polyhedral water clusters, II: correlations of connectivity parameters with electronic energy and hydrogen bond lengths

Polyhedral water clusters (PWCs) are (H2O)(n) clusters in which every oxygen is three-coordinated. Four polyhedral geometries on which water clusters can be based are the cube (n = 8), pentagonal prism (n = 10), hexagonal prism (n = 12), and 4 4 5 4 octahedron (n = 12). For each of these geometries, a database was obtained of PWCs optimized at the B3LYP/6-311 + +G** level. The total database contained 1311 hydrogen bonds in 82 optimized PWCs. Using linear regression, correlations were sought linking aspects of the clusters' H-bonding pattern with their electronic energies and with the lengths of their H-bonds. Excluding six very high-energy clusters whose H-bonding pattern included a motif called a cyclic component, 98.9% or more of the variance in clusters' electronic energy could be accounted for by just three connectivity parameters, for each of the geometries. Five families of H-bonds were distinguished based on the presence or absence of a pendent H on the acceptor and donor 0 and on the layout of adjacent H's. Within each family, the presence or absence of pendent H's on first and second neighbor O's accounted for 86-95% of the variance in H-bond length, and could be used to predict H-bond length with an RMS error less than or equal to2.4 pm. (C) 2002 Elsevier Science B.V. All rights reserved.