Structure and magnetic studies of a two-dimensional sheet-like copper(II) complex with bridging pyridine-4-carboxylate and trans-oxamidate ligands

The complex polymer [{Cu2L(pyca)(H2O}n][ClO4]n·2nH2O [H2L =N, N′-bis(2-ammoethyl)oxamide. Hpyca = pyridine-4-carboxylic acid] has been prepared and its magnetic properties and crystal structure determined. The crystals are monoclinic, space group P21/c, with 3 = 10.420(2), b= 13.118(2), c= 14.863(5)A;, β= 93.05(2)°, and Z= 4. The structure consists of a two-dimensional network of copper(II) ions bridged by the bis(tridentate) ligand L in trans conformation, and by pyridine-4-carboxylate where the carboxylate group is bonded to three different copper centres in a novel manner. The repeating asymmetric unit is a binuclear copper(II) fragment with one of the metal centres in an octahedral environment whereas the other is in a distorted square-based pyramidal geometry. From magnetic susceptibility measurements the complex was found to exhibit a strong antiferromagnetic coupling with J=–486 cm –1 and θ=–15 K, due to the efficiency of the oxamidate and triatomic anti-anti carboxylate bridges in propagating antiferromagnetic exchange interaction between the copper(II) ions which are separated by about 5.2 and 6.9 A, respectively.