Copper(II)-N-hydroxy-N,N′-diarylformamidine complexes: Synthesis, crystal structures, antibacterial and molecular docking studies

Abstract

A series of Cu(II) complexes were synthesized by using N-hydroxy-N,N′-diarylformamidine ligands: N-hydroxy-N,N′-(phenyl)formamidine (L1), N-hydroxy-N′-(4-methylphenyl)formamidine (L2), N-hydroxy-N,N′-(2,6-dimethylphenyl)formamidine (L3), N-hydroxy-N,N′-(2,6-diisopropylphenyl)formamidine (L4). Reaction of ligands L1–L4 with hydrated copper acetate furnished mononuclear Cu(II) complexes 1–4 with general formula [Cu-(L)2]. The molecular structures of complexes 3 and 4, as determined by single crystal X-ray diffraction, showed both to have square planar geometry with a near C2 symmetry. The antimicrobial potency of all four complexes was evaluated against three gram-(–) bacteria (S. typhimurium, P. aeruginosa, and E. coli) and two gram-(+) bacteria (Methicillin-resistant S. aureus (MRSA) and S. aureus), with ciprofloxacin as the reference drug. All tested complexes were inactive against gram-(+) bacteria strains except for complex 1, which displayed excellent activity when compared to the reference. Molecular docking studies showed that hydrogen bonding, pi-sigma and van der Waals interactions are prominent complex-protein connections, with complex 2 displaying good binding affinities with the studied biological targets.