Synthesis and Magnetic Studies of μ‐Oxamido‐bridged Copper(II)–Manganese(II) Heterobinuclear Complexes

Abstract 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 (NO2phen), 2,9‐dimethyl‐1,10‐phenanthroline (Me2phen) or 5‐phenyl‐1,10‐phenanthroline (Phphen), respectively; namely, [Cu(dmoxae)Mn(NO2phen)2](ClO4)2 (1), [Cu(dmoxae)Mn(Me2phen)2](ClO4)2 (2), and [Cu(dmoxae)Mn(Phphen)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, Hˆ= − 2Sˆ1 · Sˆ2, 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.