The crystal-field energy levels of some bis(ethylenediamine)copper(II) complexes

Abstract

The polarised single-crystal electronic spectra and e.s.r. spectra of six bis(ethylenediamine)copper(II) complexes have been interpreted in terms of a crystal field of D_2h symmetry. The equatorial x- and y-co-ordinate axes were found to lie close to the copper–ligand bonds rather than between them, giving rise to a d_x²–y² ground state. In the Cu en₂X₂ complexes the sequence of one-electron energy levels is d_x²–y² > d_z² > d_xzd_yz with the position of the d_xy orbital less certain, but probably lying between the d_z² and d_xz,d_yz levels. From the single-crystal e.s.r. spectra and the electronic energy levels the orbital reduction factors k_⊥ and k_∥ have been determined, and interpreted as molecular orbital coefficients.