QUANTUM CHEMICAL STUDY OF THE HCL MOLECULE AND ITS BINARY COMPLEXES WITH CO, C2H2, C2H4, PH3, H2S, HCN, H2O AND NH3 - HYDROGEN-BONDING AND ITS EFFECT ON THE CL-35 NUCLEAR-QUADRUPOLE COUPLING-CONSTANT

The results of ab initio quantum chemical calculations are reported on the HCl molecule and the hydrogen bonded complexes B...HCl, where BCO, C2H2, C2H4, PH3, H2S, HCN, H2O and NH3. The main emphasis of this work is the accurate calc of the 35Cl nuclear quadrupole coupling constants, using SCF and averaged coupled pair functional methods, accounting for the electrical and geometrical polarization effects as well as librational averaging. Other quantities of interest that were calculated and compared with experiment include a range of one-electron properties for the HCl molecule such as its dipole and quadrupole moments, polarizability, the chlorine electric field gradient response tensors as well as derivatives of the field gradient. For the complexes the binding energies, dipole moment shifts, changes in the HCl bond length as well as in its stretching frequency and intensity are also reported. The overall agreement between theory and experiment, where comparison is possible, is very good. The hydrogen bonding and its effects on the dipole moment and the Cl field gradient are also analysed into electrostatic, exchange, polarization and charge transfer contributions using the Morokuma method and the constrained spatial orbital variation approach; these calculations convincingly demonstrate the importance of intermolecular exchange, especially with regard to the Cl field gradient. © 1990.