Synthesis, spectral and magnetic studies of copper(II)–manganese(II) heterobinuclear complexes bridged by oxamido groups

Abstract

Two new μ-oxamido-bridged heterobinuclear complexes have been synthesized and identified as [Cu(dmoxpn)Mn(Me 2phen) 2](ClO 4) 2 ( 1) and [Cu(dmoxae)Mn(Me 2phen) 2](ClO 4) 2 ( 2), where Me 2phen denotes 2,9-dimethyl-1,10-phenanthroline; dmoxpn and dmoxae represent N, N′-bis[3-(dimethylamino)-propyl]oxamido and N, N′-bis[2-(dimethylamino)ethyl]oxamido dianions, respectively. Based on elemental analyses, conductivity measurements, IR and electronic spectra studies, it is proposed that the two complexes have oxamido-bridged structures consisting of a copper(II) and a manganese(II) ions, which have a square-planar environment and a distorted octahedral environment, respectively. The electronic reflectance spectra indicate the presence of exchange-coupling interaction between bridging copper(II) and manganese(II) ions. Variable-temperature magnetic susceptibility (4.2–300 K) measurements of ( 1) and ( 2) complexes revealed the occurrence of an intramolecular antiferromagnetic interaction between the adjacent manganese(II) and copper(II) ions through the oxamido bridge within each molecule. On the basis of spin Hamiltonian, H ̂ =−2J S ̂ 1· S ̂ 2 the magnetic analysis was carried out for the two complexes and the spin coupling constant ( J) was evaluated as −26.9 cm −1 for ( 1) and −38.2 cm −1 for ( 2). The influence of the chelate ring arrangement around the copper(II) in the copper(II)–manganese(II) heterobinuclear complexes on magnetic interactions between the metal ions of this kind of complexes is also discussed.