Some new Cu(II) complexes containing O,N-donor Schiff base ligands derived from 4-aminoantipyrine: synthesis, characterization, crystal structure and substitution effect on antimicrobial activity

A new series of mononuclear Cu(II) complexes, [Cu(L-1)(2)]: C1, [Cu(L-2)(2)]: C2, [Cu(L-3)(2)]: C3 and [Cu(L-4)(2)]: C4, with bis-O,N-bidentate Schiff base ligands (HL1 : (E)-4-[(2-hydroxy-5-bromobenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL2 : (E)-4-[(2-hydroxy-5-chlorobenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL3 : (E)-4-[(2-hydroxy-5-hydroxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one; HL4 : (E)-4-[(2-hydroxy-5-nitrobenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) have been prepared and characterized by elemental (CHN) analyses, FT-IR and multinuclear NMR (H-1 and C-13) spectroscopy. Furthermore, the crystal structures of HL3 , HL4 and C4 were analyzed by single-crystal X-ray diffraction (SC-XRD). The XRD studies revealed that C4 has 2:1 ligand-to-metal ratio and adapts highly distorted square planar geometry. The in vitro antibacterial activities of the synthesized ligands and their respective copper(II) complexes were elaborated by screening them against Staphylococcus aureus and Escherichia coli. The results showed a wide range of antimicrobial activity due to different electronic environments of the substituents on phenolic moiety.

Automated summary

A series of new mononuclear Cu(II) complexes with bis-O,N-bidentate Schiff base ligands have been synthesized and characterized, with C4 showing a highly distorted square planar geometry. Antibacterial activity studies revealed a wide range of antimicrobial activity due to different electronic environments of the substituents on the phenolic moiety.