Synthesis and magnetic studies of μ-oxamido-bridged copper(Il)-manganese(II) heterobinuclear complexes

Three new copper(II)-manganese(II) heterobinuclear complexes bridged by N,N'-bis[2-(dimethylamino)ethyl]oxamido dianion (dmoxae) and end-capped with 5-nitro-1,10-phenanthroline (NO(2)phen), 2,9-dimethyl-1,10-phenanthroline (Me(2)phen) or 5-phenyl-1,10-phenanthroline (Php-hen), respectively; namely, [Cu(dmoxae)Mn(NO(2)phen)(2)](ClO4)(2) (1), [Cu(dmoxae)Mn(Me(2)phen)(2)](ClO4)(2) (2), and [Cu(dmoxae)Mn(Php-hen)(2)](ClO4)(2) (3); have been synthesized and characterized by elemental analyses, IR and electronic spectral studies and molar conductivity measurements. It is proposed that these complexes have oxamido-bridged structures consisting of planar copper(II) and octahedral manganese(II) ions. The electronic reflectance spectra indicate the presence of exchange-coupling interaction between bridging copper(II) and manganese(II) ions. The cryomagnetic measurements (4.2-300 K) of the three complexes demonstrated the operation of antiferromagnetic interaction between the adjacent manganese(II) and copper(II) ions through the oxamido-bridge within these copper(II)-manganese(II) heterobinuclear complexes. On the basis of the spin Hamiltonian, (H) over cap = -2 (S) over cap (1).(S) over cap (2), a magnetic analysis was carried out for the three complexes and the spin-coupling constant (J) was evaluated as - 39.7 cm(-1) for (1), -38.5 cm(-1) for (2), and -37.8 cm(-1) for (3). The influence of methyl substituents in amine groups of the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.