Molecular orbital studies of gas-phase interactions between complex molecules

The gas-phase interactions between a linear nonionic oligomer and various model compounds (cofactors) are investigated by using PM3 semiempirical molecular orbital theory. The bond lengths, bond angles, delocalized molecular orbitals (DLMOs), and electron densities for the poly(ethylene oxide) (PEO)/cofactor complexes are consistent with hydrogen bonds, but the number of intermolecular R-OH...O and R-CH...O bonds do not correlate with the enthalpy of association.