Ab initio MRSDCI calculations of the g-tensor components of [Cu(H2O)6] complexes

The geometrical structure, electronic states and g-tensor values of the hydrated Cu²⁺ ion, Cu(H₂O)₆]²⁺ complex, have been studied by means of ab initio MO and MRSDCI methods. The ground state potential energy surface calculated as functions of the axial and equatorial Cu---O bond distances (r_ax and r_eq) show two energy minima which correspond to elongated and compressed structures of the Cu(H₂O)₆]²⁺ complex. For the elongated structure, the optimized geometry and ratio of the bond lengths (r_ax/r_eq) were in good agreement with the structure determined by ESR and the EXAFS experiments. On the basis of second-order perturbation theory, g-tensor components of the complexes were calculated with the natural orbitals obtained by an MRSDCI calculation. For the elongated structure, the g value is larger than g_τ (g = 2.400 and g_τ = 2.098) which is in agreement with the ESR experiment.