Exchange interaction and orbital degeneracy in the Cu(II)-Co(II) heterobinuclear complex

The temperature dependence of the magnetic susceptibility of the title compound was studied in the range 3.6–300 K. This heterobinuclear complex may be considered as the simplest polynuclear system in which the problem of the orbital degeneracy occurs. The experimental data were interpreted with a hamiltonian taking into account the distorsion and the spin-orbit coupling around the Co(II) ion on one hand, and the Cu(II)-Co(II) interaction on the other. From this hamiltonian, a quite satisfying simulation of the experimental magnetic curve was obtained. The effective exchange interaction parameter J of the ?J?_Cu?_Co term of the hamiltonian was found equal to =62 ± 2 cm^?1. This value was compared to those obtained with the [CuCu], [CuNi] and [CuMn] complexes prepared with the same bichelating ligand. This comparison was carried out in a framework of an orbital model, previously established in the case of interacting ions without orbital momentum and here extended to the case where one of the interacting ions has an orbital degeneracy.