Ab initio MRSDCI calculations of the g-tensor components of [Cu(H2O)6]2+ 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 (rax and req) 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 (rax/req) 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 gτ (g‖ = 2.400 and gτ = 2.098) which is in agreement with the ESR experiment.