Electronic and electron spin resonance spectra of dihydrogenethylene-diaminetetra-acetatoaquocopper(II) and bis(diethylenetriamine)copper-(II) bromide monohydrate

Abstract

The polarised single-crystal electronic spectra and e.s.r. spectra of Cu H₂edta (H₂O) and Cu dien₂Br₂,H₂O have been measured, both have been interpreted in D₂ symmetry and the interpretation of the latter in C_2v symmetry is discussed. The polarisation data from Cu H₂edta (H₂O) yields the tentative one electron-orbital sequence d_xy > d_z² > d_xz > d_x²–y² > d_yz and that from Cu dien₂Br₂,H₂O, the tentative sequence d_x–y² > d_z² > d_xy > d_yz. The ground states correspond with the x and y axes bisecting the angles between the equatorial bonds in the former complex, but lying along the bonds in the latter.

The combined orbital and spin-orbit reduction parameters (k) are calculated for Cu H₂edta (H₂O). The energy levels for both complexes are discussed in terms of the restricted tetragonal distortion imposed by the presence of ligands which are involved in chelation out of the equatorial plane. A corresponding interpretation of the electronic spectra of Cu en₃SO₄ and Cu bipy₃Br₂,6H₂O is suggested. The effect of a d_x²–y² and a d_xy ground state on the relative intensities of the x-, y-, and z-polarised spectra are discussed.