Single-crystal electronic and electron spin resonance spectra of bis-(diethylenetriamine)copper(II) nitrate

Abstract

The polarised single-crystal electronic spectra and e.s.r. spectrum of Cu(dien)₂(NO₃)₂ are interpreted in C₂ effective symmetry, with a d_z² ground-state. This yields the one-electron orbital sequence d_z² > d_x²–y², d_xy > d_xz, d_yz; the precise order of the d_x²–y² and d_xy levels is not certain, but that with the d_x²–y² above the d_xy level is preferred. The low energy of the d_x²–y²→d_z² transition reflects the small ‘ tetragonal ’ distortion arising from the out-of-plane chelation of diethylenetriamine. A method is given for calculating the molecular g-values, for rhombic symmetry, from data on crystals containing four inequivalent orientations.