QUANTUM-CHEMICAL STUDIES OF THE PYRROLE-WATER AND PYRIDINE-WATER COMPLEXES

An ab initio quantum chemical study of the hydrogen bonded binary comp lexes pyrrole-water and pyridine-water is reported. The calculations w ere performed largely at the MP2 level of theory using basis sets of d ouble-zeta-plus polarization functions quality and focus on properties of the complexes such as molecular geometries, energies, harmonic vib rational frequencies, dipole moments and N-14 nuclear quadrupole coupl ing constants. Where possible, the results of the calculations are com pared with experimental data. In addition, the interaction potentials are studied in some detail, specifically with regard to basis set supe rposition and its effect on geometries, intermolecular vibrational fre quencies and binding energies. The nature of interaction, i.e., the im portance of electrostatic, Pauli repulsion, polarization, charge trans fer and dispersion contributions to the hydrogen bond energies, as obt ained in constrained spatial orbital variation analyses, is also discu ssed.