Four heteronuclear complexes Mn(CuL)(2)(SCN)(2) (1), {[Mn(CuL)(2)(mu-dca)(2)]center dot 2H(2)O}(n) (2), Zn(CuL)(2)(SCN)(2) (3), and [Fe(CuL)(N-3)(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]-tetraazacyclotetradec ine-13,18-dicarboxylate, and dca is the dicyanamide. The structure of 1 or 3 consists of oxamido-bridged trinuclear [(MCu2II)-Cu-II] 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 pi-pi interactions. The structure of 2 also has the oxamido-bridged trinuclear [(MnCu2II)-Cu-II] structure units and consists of 2D layers formed by the linkage of copper(II) and manganese(II) atoms via the oxamido and mu(1, 5)-dca bridges. Complex 4 consists of oxamido-bridged tetranuclear [(Fe2Cu2II)-Cu-II] 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.