Heteronuclear Complexes of Macrocyclic Oxamide with Co-ligands:  Syntheses, Crystal Structures, and Magnetic Properties

Four heteronuclear complexes Mn(CuL)₂(SCN)₂ (1), {[Mn(CuL)₂(μ-dca)₂]·2H₂O}_n (2), Zn(CuL)₂(SCN)₂ (3), and [Fe(CuL)(N₃)₂]₂ (4) incorporating macrocyclic oxamide ligands have been synthesized and structurally characterized. L is the dianion of diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]-tetraazacyclotetradecine-13,18-dicarboxylate, and dca is the dicyanamide. The structure of 1 or 3 consists of oxamido-bridged trinuclear [M^IICu^II₂] molecules (for 1, M is the manganese(II) ion, and for 3, M is the zinc(II) ion). Both of them consist of 1D supramolecuar chains via π−π interactions. The structure of 2 also has the oxamido-bridged trinuclear [Mn^IICu^II₂] structure units and consists of 2D layers formed by the linkage of copper(II) and manganese(II) atoms via the oxamido and μ_{1, 5}-dca bridges. Complex 4 consists of oxamido-bridged tetranuclear [Fe^II₂Cu^II₂] molecules and arranges in 1D chains. Different co-ligands may result in different structures in this macrocyclic oxamide system. The variable-temperature magnetic susceptibility measurements (2−300 K) of 1 and 2 both show the pronounced antiferromagnetic interactions between the copper(II) and manganese(II) ions.