Abstract:
SCF-MS-Xα calculations of the electronic structure of the oxy-halogen compounds Cl2O, ClO, ClO2, ClO2−, ClO3−, ClO4−, BrO, BrO2, BrO3−, IO3−, and IO4− have been used to investigate the bonding and nuclear quadrupole coupling in these molecules and ions. The halogen d orbital participation in the bonding increases with increasing oxidation number of the halogen atom in the molecule or ion. The inclusion of the halogen d orbitais results in an increase in the principal component of the halogen electric field gradient tensor, but only in some cases this result in improved agreement between the calculated and observed halogen nuclear quadrupole coupling constants. In other cases better agreement is obtained for calculations involving the halogen p orbitais only in the valence shell. Thus the results do not provide unambiguous evidence for the involvement of halogen d orbitais in the bonding. In the case of the ClO3− and BrO3− ions for which 17O quadrupole coupling constants have been reported, the Xα values have been calculated. Agreement between the calculated and observed values is much poorer than for the halogen coupling constants. The results of the calculations have also been used to investigate some of the approximations made in the Townes and Dailey method of analysis of nuclear quadrupole coupling data.
