Superoxide dismutase activity of ternary copper complexes of sulfathiazole and imidazole derivatives.: Synthesis and properties of [CuL2(R-Him)2] [HL=4-amino-N-(thiazol-2-yl)benzenesulfonamide, R-Him=4-methylimidazole, 4,4-dimethylimidazoline or 1,2-dimethylimidazole].: Crystal structure of [CuL2(4,4-dimethylimidazoline)2]

New ternary copper(II) complexes of sulfathiazole (4-amino-N-(thiazol-2-yl)benzenesulfonamide)(HL) and methyl imidazole derivatives have been synthesised and characterised. The crystal structure of the complex [CuL2(4,4-dmHim)(2)] (1) [4,4-dmHim = 4,4-dimethylimidazoline] has been determined. The copper centre has a quasi regular square planar environment with Cu-nitrogen bond lengths ranging from 1.952 to 2.010 Angstrom. From the spectroscopic properties of the complexes [CuL2(1,2-dmHim)(2)] (2) [1,2-dmHim = 1,2-dimethylimidazole] and [CuL2(4-mHim)(2)] (3) [4-mHim = 4-methylimidazole] a distorted tetragonal octahedral geometry is deduced. The compounds showed SOD mimetic activity in fact, a low concentration of the complexes catalyses the dismutation of superoxide at biological pH. This SOD activity is correlated with their structural properties. Using Extended Huckel Molecular Orbital Calculations the one-electron energy levels of the CuN4 chromophore in complex 1 are reported and correlated with the data of the CuN6 and CuN5 chromophores of the previously reported [CuL2(Him)(2)]. MeOH and [CuL2(mim)(2)]. H2O compounds. In addition, the influence of the geometry distortion on the composition and energy of the molecular orbitals is described using idealised models. (C) 2000 Elsevier Science S.A. All rights reserved.