Molecular orbital studies of C-H...O hydrogen-bonded complexes

Abstract

Fully optimized ab initio and semiempirical molecular orbital calculations are reported on complexes containing C-H...O interactions that are prototypes of interactions commonly found in crystals. The ab initio calculations were performed both at the Hartree-Fock (HF) and second-order MOller-Plesset (MP2) levels using the 6-31G(d,p) and D95++(d,p) basis sets. The semiempirical calculations used the AM1, PM3, and SAM1 methods. The complexes considered are those of acetylene or hydrogen cyanide with water, formaldehyde, and ozone. The interaction energies, geometries, and vibrations are presented with corrections for zero-point vibration energy (ZPVE), basis set superposition error (BSSE), and enthalpy at 298 K, where appropriate