A new class of heterobinuclear complexes: Crystal structure and magnetism of copper(II)-nickel(II) complexes incorporating two different macrocyclic ligands

Three novel oxamido-bridged heterobinuclear copper(II)-nickel(II) complexes incorporating two different tetraazamacrocyclic compounds were synthesized and characterized by IR, ESR, and electronic spectra. They are of the formulas [(CuL¹)Ni(rac-cth)](ClO)₄₂·H₂O (1), [Cu(L²)Ni(rac-cth)](ClO₄)₂·0.5 EtOH (2), and [(CuL³)Ni(rac-cth)](ClO₄)₂·H ₂O (3). L¹, L², and L³ are the dianions of diethyl 5,6,7,8,16,17-hexahydro-6,7-dioxo-15H-dibenzo[e,n][1,4,8,12] tetraazacyclopentadecine-13,19-decarboxylate, diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11] tetraazacyclotetracine-13,18-decarboxylate, and diethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11] tetraazacyclotetracine-13,18-decarboxylate, respectively, and rac-cth is rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. The Ni^II ion is pseudooctahedrally coordinated. The coordination geometry around the Cu^II ion in 2 is slightly distorted square planar, while that in 1 shows significant distortion towards a tetrahedral structure. The temperature dependence of the magnetic susceptibility for 1 and 2 was analyzed by means of the Hamiltonian Ĥ = - 2JŜ₁·Ŝ₂, leading to J = - 63.9 and -67.4 cm^-1 for 1 and 2, respectively.