Syntheses, characterizations, X-ray crystal structures, and antibacterial activities of Co( II), Ni( II), and Zn( II) complexes of the Schiff base derived from 5-nitro-2hydroxybenzaldehyde and benzylamine

Three new complexes, [(CoL2)-L-II(bzln)(2)] (1), [(NiL2)-L-II(DMF)(2)] (2), and [(ZnL2)-L-II] (3), with the bidentate (NO) Schiff base HL=2-((E)-(benzylimino)methyl)-4-nitrophenol have been synthesized and characterized. [(CoL2)-L-II(bzln)(2)] (1) was initially formed from the reaction of H2L1 (N,N-bis(5-nitrobenzaldehyde)-2-aminobenzylamine=H2L1), with Co-II(CH3COO)(2)4H(2)O in the presence of benzylamine. The X-ray crystal structure of 1 revealed that HL was formed from the hydrolysis of H2L1 and the recondensation of benzylamine with 2-hydroxy-5-nitrobenzaldehyde produced in H2L1 hydrolysis. The Schiff base HL was then prepared by direct reaction of 2-hydroxy-5-nitrobenzaldehyde and benzylamine. Complexes 1-3 were also directly synthesized and their crystal and molecular structures determined by X-ray crystallography. The ligand and its metal complexes were also screened for in vitro antibacterial activity.