STRUCTURE AND MAGNETIC-PROPERTIES OF A SYN-ANTI CARBOXYLATE BRIDGED LINEAR TRINUCLEAR COPPER(II) COMPLEX WITH FERROMAGNETIC EXCHANGE INTERACTION

The synthesis, crystal structure and magnetic properties are reported for the trinuclear compound [CU(H2O)4{Cu(HL)(H2O)(ClO4)}2][ClO4]2.2H2O, where HL is the monodeprotonated form of 6-methylamino-1,3-dimethyl-5-[(2'-carboxyphenyl)azo]uracil. The compound crystallizes in the triclinic system, space group P1BAR, with cell constants a = 7.824(3), b = 12.278(3), c = 13.705(9) angstrom, alpha = 104.34(3), beta = 91.80(3), gamma = 103.37(5)-degrees and Z = 1. The structure was solved and refined to R = 0.071 (R(w) = 0.064). The structure consists of trinuclear [Cu(H2O)4{Cu(HL)(H2O)(ClO4)}2]2+ cations, non-coordinated perchlorate anions and crystal water molecules, held together by a network of hydrogen bonds. The central copper is in an elongated octahedral CuO6 chromophore and the terminal copper atoms in distorted square-pyramidal CuNO4 chromophores. Adjacent copper atoms are linked by carboxylate groups in a syn-anti conformation. From the magnetic susceptibility measurements, the complex is found to exhibit weak ferromagnetic interaction between nearest-neighbour copper(II) ions. The magnitude and nature of the exchange coupling are discussed on the basis of the structural data.