Synthesis, Spectroscopic Studies and Biological Activity of Cu(II) Complex of Schiff Base Ligand 3-((2-(2,4-dinitrophenyl)hydrazineylidene)methyl)pyridine with Triphenylphosphine as Ancillary Ligand

Abstract

In this study we synthesized, characterized, and evaluated the antibacterial activity of a new mixed-ligand Cu(II) complex containing a Schiff base derived from 3-pyridinecarboxaldehyde and 2,4-dinitrophenylhydrazine, together with triphenylphosphine as ancillary ligand. The compound was characterized using Fourier Transform Infrared (FTIR) spectroscopy, UV-Visible spectroscopy, and magnetic susceptibility measurements. Antibacterial screening was carried out using agar well diffusion method against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. FTIR analysis confirmed coordination through the azomethine and pyridyl nitrogen atoms with characteristic bands at 1618 and 1584 cm⁻¹, while retaining nitro group absorptions at 1508 and 1325 cm⁻¹. The complex displayed an average inhibition zone of 26.25 mm, surpassing the standard drug Ofloxacin (23.50 mm) and showing significant enhancement over the free ligands and copper salt. Magnetic susceptibility measurements revealed paramagnetic behaviour. The synthesized heteroleptic Cu(II) complex demonstrated excellent broad-spectrum antibacterial activity, highlighting the synergistic effect of the Schiff base and triphenylphosphine ligands.