STRUCTURE AND MAGNETIC STUDIES OF A 2-DIMENSIONAL SHEET-LIKE COPPER(II) COMPLEX WITH BRIDGING PYRIDINE-4-CARBOXYLATE AND TRANS-OXAMIDATE LIGANDS

The complex polymer [{Cu(2)L(pyca)(H2O)}(n)][ClO4](n).2nH(2),O [H(2)L = N,N'-bis(2-aminoethyl) oxamide Hpyca = pyridine-4-carboxylic acid] has been prepared and its magnetic properties and crystal structure determined: The crystals are monoclinic, space group P2(1)/c, with a = 10.420(2), b = 13.118(2), c = 14.863(5) Angstrom, beta = 93.05(2)degrees, 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 theta = -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 Angstrom, respectively.