X.alpha. calculations of the EPR parameters of pseudotetrahedral copper(II) complexes

The self-consistent-field multiple-scattering Xa method has been used to calculate the electronic structure of pseudotetrahedral and square-planar CuCI4*- ions, with the aim of checking the reliability of the method in the calculation of the spectral (electronic and EPR) properties of transition metal complexes. Several different calculation schemes were used in order to improve the fit to the experimental spectral transitions. Overlapping spheres were found to give the best agreement. The values of g and of the 63Cu hyperfine constant were satisfactorily reproduced, showing that the low value of the latter in the pseudotetrahedral ion is due to covalency effects and not to 4p metal orbital mixing into the ground state.