Water: new aspect of hydrogen bonding in the solid state.
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abstract
All water-water contacts in the crystal structures from the Cambridge Structural Database with d OO 4.0 have been found. These contacts were analysed on the basis of their geometries and interaction energies from CCSD(T)/CBS calculations. The results show 6729 attractive water-water contacts, of which 4717 are classical hydrogen bonds (d OH 3.0 and 120) with most being stronger than -3.3kcalmol-1. Beyond the region of these hydrogen bonds, there is a large number of attractive interactions (2062). The majority are antiparallel dipolar interactions, where the O-H bonds of two water molecules lying in parallel planes are oriented antiparallel to each other. Developing geometric criteria for these antiparallel dipoles (1, 2 160, 80 140 and T HOHO > 40) yielded 1282 attractive contacts. The interaction energies of these antiparallel oriented water molecules are up to -4.7 kcalmol-1, while most of the contacts have interaction energies in the range -0.9 to -2.1 kcalmol-1. This study suggests that the geometric criteria for defining attractive water-water interactions should be broader than the classical hydrogen-bonding criteria, a change that may reveal undiscovered and unappreciated interactions controlling molecular structure and chemistry.
