Synthesis of and magnetic interactions in binuclear Cu(II)-M(II) (M = Cu, Ni and Mn) complexes of macrocyclic oxamido ligands

Six oxamido-bridged binuclear Cu(II)-M(II) (M = Cu, Ni and Mn) complexes containing macrocyclic oxamido ligands have been synthesized and characterized by IR, ESR and electronic spectra. They are of the formula [Cu(L²)M(L)_n](CIO₄)₂, where H₂L² = 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis (ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, L=2,2′-bipyridine and 1,10-phenanthroline (phen), n = 1 for M = Cu and n = 2 for M = Ni and Mn. The magnetic properties of the complexes with L = phen have been investigated and quantitatively interpreted using the Hamiltonian Ĥ = - 2JŜ₁ · Ŝ₂, suggesting antiferromagnetic interactions through the oxamido bridge with J = - 210.2, - 53.9 and - 14.1 cm^-1 for the Cu₂, CuNi and CuMn complexes, respectively. Finally, the magnitudes of the Cu(II)-M(II) interactions with M = Cu, Ni and Mn have been compared and qualitatively justified.