STRUCTURAL AND MAGNETIC STUDIES OF A SYN-ANTI CARBOXYLATE-BRIDGED HELIX-LIKE CHAIN COPPER(II) COMPLEX

The preparation, magnetic properties, and crystal and molecular structure of [CuL(H2O)]n are described (L stands for the doubly deprotonated form of 1,3-dimethyl-5-((2-carboxyphenyl)azo)barbituric acid). The crystals are orthorhombic, of space group P2(1)2(1)2(1), with cell constants a = 8.171 (1) angstrom, b = 10.302 (3) angstrom, c = 17.006 (5) angstrom, and Z = 4. The structure was solved and refined to R = 0.052. The copper(II) ions are in a distorted square-pyramidal environment. They are sequentially bridged by carboxylate groups in the syn-anti conformation, resulting in the formation of infinite zigzag (or helix-like?) chains running parallel to the a axis. From magnetic susceptibility measurements, the complex is found to exhibit ferromagnetic intrachain interactions with an exchange coupling of J/k = 4.8. Magnetic and structural parameters of this and other related complexes are compared, and some magneto-structural trends are discussed.