Structural, Characterization, Biological, and Studying the Enzyme Activity of Some Transition Metal Complexes with (Z)-N'-(4-Hydroxy-3,5-Dimethoxybenzylidene) Isonicotinohydrazide

The new Schiff base ligand N'-(4-hydroxy-3,5-dimethoxybenzylidene) isonicotinohydrazide (L՜) has been prepared through the condensation of isonicotinohydrazide in combination with 4-hydroxy-3,5-dimethoxybenzaldehyde and identified via FT-IR, UV-Vis spectroscopy, 1H and 13C NMR spectra, and microanalysis (CHN). Furthermore, four metal complexes, including cobalt (II), nickel (II), and palladium (II) ions, have also been synthesized and characterized using FT-IR, UV-Vis spectroscopy, magnetic susceptibility, molar conductivity measurement, and chloride content. These studies show that the molar ratio [L:M] was [2:1] for all complexes. The cobalt (II) and nickel (II) complexes had an octahedral geometry coordinated by the ligand (O, N) in a bidentate mode, whereas Cu (II) and Pd (II) had a square planar geometry. The activity of the enzyme for the ligand (L՜) and its complexes via the esterase AST was additionally examined. The enzyme activity study showed that the ligand's metal complexes exhibited diverse inhibition behaviors. The prepared (L՜) ligand and its metal complexes were tested against the fungus Candida albicans and microorganisms, including G+ bacteria (Staphylococcus aureus and Enterococcus spp.) and G- bacteria (E. coli and Pseudomonas aeruginosa). [Pd(L՜)2]Cl2 showed good antibacterial activity against Candida albicans, E. coli, and Pseudomonas aeruginosa