Hydrogen bonding. Part 85: DFT molecular orbital study of C2h (H2O·X−)2 clusters – Multicenter bonding may account for stability of (H2O·F−)2 species

Water is extraordinarily tightly bound in the C2h (H2O·F−)2 clusters found in tetraalkylammonium fluoride monohydrates. This stability, coupled with infrared spectral differences, sets the fluoride clusters apart from similarly formulated clusters of higher halide monohydrates. DFT molecular orbital analysis (B3LYP/6-31++G∗∗) shows stronger hydrogen bonds and unique orbital differences for the fluoride cluster compared to chloride or bromide analogs, and suggests the presence of eight-atom multicenter bonding in the fluoride cluster.