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]

Abstract 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 [CuL 2 (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 A. From the spectroscopic properties of the complexes [CuL 2 (1,2-dmHim) 2 ] ( 2 ) [1,2-dmHim=1,2-dimethylimidazole] and [CuL 2 (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 CuN 4 chromophore in complex 1 are reported and correlated with the data of the CuN 6 and CuN 5 chromophores of the previously reported [CuL 2 (Him) 2 ]·MeOH and [CuL 2 (mim) 2 ]·H 2 O compounds. In addition, the influence of the geometry distortion on the composition and energy of the molecular orbitals is described using idealised models.