Synthesis, characterization and antioxidant activity of new dibasic tridentate ligands: X-ray crystal structures of DMSO adducts of 1,3-dimethyl-5-acetyl-barbituric acid o-hydroxybenzoyl hydrazone copper(II) complex

o-Hydroxybenzoyl hydrazine and p-hydroxybenzoyl hydrazine react with 1,3-dimethyl-5-acetyl-barbituric acid in ethanol to give H2L1 (85% yield) and H2L2 (91% yield) respectively. The copper(II) complexes with DMSO adducts, [Cu(L1)(DMSO)] and [Cu(L2)(DMSO)], were prepared by the stoichiometric reaction of the CuCl2·5H2O with the H2L1 and H2L2 in a molar ratio (M:L) of 1:1 in DMSO/water mixture. All compounds have been fully characterized using conventional spectroscopic techniques. X-ray structure analysis was carried out on the [Cu(L1)(DMSO)] which crystallizes in the triclinic P-1 space group. In addition, both ligands were applied several antioxidant assays including total antioxidant activity by phosphomolybdate, ferric reducing antioxidant power (FRAP) and scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH). The results from antioxidant assays have shown that both ligands have excellent activities.