Synthesis, characterization, X-ray structures, and biological activity of some metal complexes of the Schiff base 2,2 0 -(((azanediylbis (propane-3,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol

Abstract

A pentadentate Schiff base, 2,2 0 -(((azanediylbis(propane-3,1-diyl))bis(azanylylidene))bis(methanylylid-ene))diphenol (1), has been synthesized via the reaction of salicylaldehyde withN 1 -(3-aminopropyl)pro-pane-1,3-diamine [HN(C3H6NH2)2] in absolute ethanol. Refluxing a mixture of 1with 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, 1 H NMR, 13 C 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 of1and its complexes were evaluated in vitro. Highest DPPH rad-ical-scavenging activity was observed for Fe(II)-1 with an IC50 of 0.39 mg mL 1 , followed by 1 (IC50= 3.38 ± 0.01 mg mL 1 ). Use of the b-carotene–linoleic acid bleaching assay revealed that 1has the highest antioxidant activity and has significant inhibition of lipid peroxidation with I% of 94.21 ± 0.003%, followed by Fe(II)-1and Ni(II)-1with I% of 34.29 ± 2.08% and 30.77 ± 1.91%, respectively. Antibacterial activity of1and its transition-metal complexes was investigated by use of disk diffusion assay; Zn(II)-1and Ni(II)-1exert a high inhibition of the growth of all bacterial strains with inhibition diameters ranging from 8 to 14 mm