Multiligand zinc(II) hydroxide complexes: Zn(OH)2X2Y and Zn(OH)2X1,2Y2; X = H2O, CH3OH and Y = NH3, C5H5N

As one component of our computational study of zinc-seamed pyrogallol[4]arene nanocapsules, we are investigating small mononuclear and polynuclear zinc complexes. In this article the results of our quantum chemical calculations on Zn(OH)2X2Y and Zn(OH)2X1,2Y2 complexes, where X is water or methanol and Y is pyridine or ammonia, are described. Structures and energetics obtained with the LanL2DZ vs. 6-311+G(d,p) vs. B2(pp) basis sets and DFT vs. MP2 methods are compared and contrasted. The effect of the hydroxide ligands on the preferred zinc coordination number and mode, inner- and outer-shell ligands, and hydrogen-bonding motifs is also examined. Trends in ligand binding energies are discussed. Of particular note is that the B3LYP/LanL2DZ calculations overemphasize the strength of both the conventional and unconventional hydrogen bonds.