Synthesis, characterization, X-ray structures, and biological activity of some metal complexes of the Schiff base 2,2′-(((azanediylbis (propane-3,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol

A pentadentate Schiff base, 2,2 '-(((azanediylbis(propane-3,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol (1), has been synthesized via the reaction of salicylaldehyde with N-1-(3-aminopropyl)propane-1,3-diamine [HN(C3H6NH2)(2)] in absolute ethanol. Refluxing a mixture of 1 with the hydrated acetate salts of nickel(II), zinc(II), iron(II), and copper(II) affords each of the expected M(II)-Schiff base complexes. These complexes have been characterized by means of FT-IR, H-1 NMR, C-13 NMR, and mass spectrometry as well as UV-Vis spectrophotometry and elemental analysis. In addition, the molecular structures of the copper(II) and nickel(II) complexes were determined by means of X-ray crystallography. Antioxidant and antibacterial activities of 1 and its complexes were evaluated in vitro. Highest DPPH radical-scavenging activity was observed for Fe(ll)-1 with an IC50 of 0.39 mg mL-1, followed by 1 (IC50 = 3,38 +/- 0.01 mg mL(-1)). Use of the beta-carotene-linoleic acid bleaching assay revealed that 1 has the highest antioxidant activity and has significant inhibition of lipid peroxidation with 1% of 94.21 +/- 0.003%, followed by Fe(ll)-1 and Ni(II)-1 with I% of 34.29 +/- 2.08% and 30.77 +/- 1.91%, respectively. Antibacterial activity of 1 and its transition-metal complexes was investigated by use of disk diffusion assay; Zn(II)-1 and Ni(II)-1 exert a high inhibition of the growth of all bacterial strains with inhibition diameters ranging from 8 to 14 mm. (C) 2014 Elsevier Ltd. All rights reserved.