Estimation of the 35Cl NQR Frequencies of Some Organic and Organometallic Molecules Using ab initio Calculations at Different Levels and Basis Sets

Ab initio calculations of organic and organometallic molecules at RHF, B3LYP and MP2 levels and 6-31G(d), 6-31+G(d), 6-311G(d) and 6-311+G(d) basis sets were executed. They were used to estimate the 35Cl NQR frequencies of these molecules. A satisfactory agreement between experimental and estimated NQR frequencies was obtained for the populations of the less diffuse 3p-components of the Cl atom valence p-orbitals obtained from the RHF, B3LYP and MP2 calculations with the split valence basis sets 6-31G(d) and 6-31+G(d). An analogous conformity was not obtained using the 6-311G(d) and 6-311+G(d) basis sets.

Temperature Dependence Studies of 35Cl NQR Frequencies in Magnesium and Nickel Hexachlorotellurate(IV) Hexahydrates and Nickel Hexachloroiridate(IV) Hexahydrate

The 35Cl NQR frequencies in MgTeCl6 · 6H2O, NiTeCl6 · 6H2O, and NiIrCl6 · 6H2O have been determined at various temperatures. These compounds form rhombohedral crystals with the space group R3̄ ,showing a single resonance line. The 35Cl NQR frequencies of the Te(IV) complexes exhibit an unusual positive temperature coefficient. The deuterated analogs of the Te(IV) complexes show a small frequency shift at 77 K. These results are interpreted by the presene of O-H ··· CI type weak H-bonds. The resonance frequency of the Ir(IV) complex versus temperature curve shows a minimum and a maximum. This unusual temperature dependence is mainly explained by the same type of the H-bond as existing in the Te(IV) complexes. The π-bond formation between Ir and CI atoms is also partly responsible for the unusual temperature dependence.