Nature of one-dimensional short hydrogen bonding: Bond distances, bond energies, and solvent effects

Abstract

On the basis of recently synthesized calix[4]hydroquinone (CHQ) nanotubes which were self-assembled with infinitely long one-dimensional (1-D) short hydrogen bonds (SHB), we have investigated the nature of 1-D SHB using first-principles calculations for all the systems including the solvent water. The H-bonds relay (i.e., contiguous H-bonds) effect in CHQs shortens the (HO)-O-... bond distances significantly (by more than 0.2 Angstrom) and increases the bond dissociation energy to a large extent (by more than similar to4 kcal/mol) due to the highly enhanced polarization effect along the H-bond relay chain. The H-bonds relay effect shows a large increase in the chemical shift associated with the SHB. The average binding energies for the infinite 1-D H-bond arrays of dioles and dions increase by similar to4 and similar to9 kcal/mol per H-bond, respectively. The solvent effect (due to nonbridging water molecules) has been studied by explicitly adding water molecules in the CHQ tube crystals. This effect is found to be small with slight weakening of the SHB strength; the (HO)-O-... bond distance increases only by 0.02 Angstrom, and the average binding energy decreases by similar to1 kcal/mol per H-bond. All these results based on the first-principles calculations are the first detailed analysis of energy gain by SHIB and energy loss by solvent effect, based on a partitioning scheme of the interaction energy components. These reliable results elucidate not only the self-assembly phenomena based on the H-bond relay but also the solvent effect on the SHB strength.