ABINITIO MOLECULAR-ORBITAL CALCULATIONS OF THE INFRARED-SPECTRA OF INTERACTING WATER-MOLECULES .2. COMPLEXES OF WATER WITH CARBON-MONOXIDE AND NITROGEN

The molecular structures, interaction energies and infrared spectra of seven H2O.CO and five H2O.N2 complexes have been computed using ab initio molecular orbital theory. The most probable structures predicted by these calculations agree with the evidence obtained from gas-phase molecular spectroscopy. The infrared spectra of the various complex species are very similar to one another and to the spectra calculated for the free monomers. A limited number of relationships has been established between the calculated OH-stretching band ratios and the CO- and NN-stretching wavenumber shifts, and the computed interaction energies of the hydrogen-bonded adducts. Comparisons have been made between the wavenumbers calculated for the most probable structure in each case and those determined experimentally in cryogenic matrices. Agreement is very favourable, averaging 5-7% too high for the water submolecules and slightly too low for the CO and N2 units.