Synthesis, crystal structure, DNA binding properties and antioxidant activities of transition metal complexes with 3-carbaldehyde-chromone semicarbazone

3-Carbaldehyde-chromone semicarbazone (L) and its Cu(II), Zn(II), Ni(II) complexes were synthesized and characterized on the basis of crystal structure and other structural characterization methods. The metal ions and Schiff base ligand can form mononuclear five-coordination complexes with 1:1 metal-to-ligand stoichiometry at the metal ions as centres. The transition metal complexes may be used as potential anticancer drugs, because they bind to calf thymus DNA via an intercalation binding mode with the binding constants at the order of magnitude 105–106 M− 1, and the metal complexes present stronger DNA binding affinities than the free ligand alone. In addition, the antioxidant activities of the ligand and its metal complexes were investigated through scavenging effects for superoxide anion and hydroxyl radical in vitro, indicating that the compounds show stronger antioxidant activities than some standard antioxidants, such as mannitol and vitamin C.