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

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 C2v symmetry is discussed. The polarisation data from Cu H2edta (H2O) yields the tentative one electron-orbital sequence dxy > dz2 > dxz > dx2–y2 > dyz and that from Cu dien2Br2,H2O, the tentative sequence dx–y2 > dz2 > dxy > dyz. 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 dx2–y2 and a dxy ground state on the relative intensities of the x-, y-, and z-polarised spectra are discussed.