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

Abstract

A new series of mononuclear Cu(II) complexes, [Cu(L¹)₂]: C1, [Cu(L²)₂]: C2, [Cu(L³)₂]: C3 and [Cu(L⁴)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 (¹H and ¹³C) 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.

Graphical Abstract

Keywords:

• Aminoantipyrine
• Schiff base complex
• x-ray structure
• antibacterial activity

Acknowledgements

The support of this work by Ardakan University and Payame Noor University are gratefully acknowledged. H.K. thanks Prof. Mehmet Akkurt from Erciyes University for the X-ray analysis of complex C4.

Disclosure statement

No potential conflict of interest was reported by the authors.