DNA cleavage reaction induced by dimeric copper(II) complexes of N-substituted thiazole sulfonamides

Abstract A new dinuclear copper(II) complex has been synthesised and structurally characterised: [Cu 2 (tz-ben) 4 ] (Htz-ben =  N -thiazol-2-yl-benzenesulfonamide). Its crystal structure, magnetic properties and electronic paramagnetic resonance (EPR) spectra were studied in detail. In the compound the metal centres are bridged by four non-linear triatomic NCN groups. The coordination geometry of the copper ions in the dinuclear entity is distorted square pyramidal (4 + 1). Two thiazole N and two sulfonamido N atoms occupy the equatorial positions and one sulfonamido O atom is in the axial position. Magnetic susceptibility data show a strong antiferromagnetic coupling, −2 J  = 114.1 cm −1 . The EPR spectra of a polycrystalline sample of compound has been obtained at the X- and Q-band frequencies at different temperatures. Above 20 K the spectra are characteristic of S  = 1 species with a zero field splitting parameter D  = 0.4 cm −1 . The EPR parameters are discussed in terms of the known binuclear structures. The chemical nuclease ability of the title complex and that of the related [Cu 2 (tz-tol) 4 ] compound (Htz-tol =  N -thiazol-2-yl-toluenesulfonamide) is reported. The participation of hydroxyl radicals and a singlet oxygen-like entity in the DNA cleavage reaction has been deduced from the assays with radical oxygen scavengers.