Synthesis, crystallographic and spectroscopic characterization and magnetic properties of dimer and monomer ternary copper(II) complexes with sulfonamide derivatives and 1,10-phenanthroline. Nuclease activity by the oxidative mechanism

Three dinuclear and one mononuclear copper(II)-1,10-phenanthroline ternary complexes, [Cu(L1)(phen)(OH)]2 (1), [Cu(L2)(phen)(OH)]2·3H2O (2), [Cu(L3)(phen)(OH)]2 (3) and [Cu(L4)2(phen)(H2O)] (4), with thiadiazole sulfonamide derivative ligands: HL1 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)naphthalene-1-sulfonamide), HL2 (N-(5-ethylthio)-1,3,4-thiadiazol-2-yl)-4-methylbenzenesulfonamide), HL3 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide) and HL4 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)-4-methylbenzenesulfonamide) have been synthesized and characterized. In the four complexes each copper atom is five-coordinated. The structure of complexes 1, 2 and 3 consists of a dimeric unit with a C2 symmetry axis, where both coppers are bridged by two hydroxo anions. Magnetic measurements show that the dimer complexes are ferromagnetic according to the Cu–O–Cu angles. Cleavage experiments using pUC18 plasmid DNA in the presence of H2O2/ascorbic acid as an activating agent show that the title complexes are potent artificial chemical nucleases, the order of efficiency being 3 > 2 ∼ 1 > 4. Control cleavage experiments indicated that the dimer complexes are stronger artificial nucleases than the [Cu(phen)2]2+ complex under the same experimental conditions, while the monomer 4 has a lower nuclease activity than the [Cu(phen)2]2+ complex. The inhibition of the cleavage process in the presence of reactive oxygen intermediate scavengers suggests that the hydroxyl radical and the superoxide anion are reactive species for the breakage of the DNA strands.

Graphical abstractThree dinuclear and one mononuclear copper(II)–1,10–phenanthroline ternary complex, [Cu(L1)(phen)(OH)]2 (1), [Cu(L2)(phen)(OH)]2·3H2O (2), [Cu(L3)(phen)(OH)]2 (3) and [Cu(L4)2(phen)(H2O)] (4), have been synthesized and characterized. Magnetic measurements show that the dimer complexes are ferromagnetic according to the Cu–O–Cu angles. The title complexes are potent artificial chemical nucleases.Figure optionsDownload full-size imageDownload as PowerPoint slide