Synthesis, characterization, and biological screening of Co(II), Ni(II), Cu(II), Pd(II), and Pt(IV) complexes of a novel hydrazide–hydrazone ligand derived from gallic acid

Abstract

This work involves the synthesis of the Co(II), Ni(II), Cu(II), Pd(II), and Pt(IV) complexes (M1-M5) with a new Schiff base ligand by the condensation reaction of 3,4,5-trimethoxybenzohydrazide with 2-hydroxy-4-methoxybenzaldehyde to yield N'-(2-hydroxy-4-methoxybenzylidene)-3,4,5-trimethoxybenzohydrazide (L). The structures of the new ligand and its complexes were examined by fourier-transform infrared (FT-IR), ultraviolet-visible (UV-visible), proton nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR) spectroscopy, mass spectrometry, microelement analysis, atomic absorption flame (AAF) spectrophotometry, conductivity, and magnetic susceptibility tests. The spectroscopic and elemental analysis results revealed tetrahedral geometry around the Co(II) ion, square-planar geometry around Ni(II), Cu(II), and Pd(II), and octahedral geometry around Pt(IV). The ligand (L) and its complexes (M1-M5) were subjected to in vitro studies to test their antibacterial activities against Staphylococcus aureus as gram positive and Escherichia coli as gram negative bacteria, the (MIC) values were measured against standard antibiotics. Furthermore, the new compounds were also tested as antifungal agents against Aspergillus Flavus and Penicillium spp.