Synthesis, Characterization and Antimicriobial Activity of 1, 2-Bis ((E)-3-Phenylallylidene) Hydrazine and Its Metal Complexes

Schiff bases and associated transition-metal complexes have garnered significant interest because of their wide range of biological activity and structural adaptability. The growing problem of antibiotic resistance highlights the urgent need to discover and develop alternative antimicrobial agents. In this work, cinnamaldehyde was condensed with hydrazine hydrate to form 1,2-bis (E-3-phenylallylidene)hydrazine (ca), which was then coordinated with Cu(II), Co(II), Mn(III), and Zn(II) ions. Metal analysis, infrared spectroscopy, UV-visible spectroscopy, and magnetic susceptibility measurements were used to characterise the synthesised ligand and its metal complexes. Spectroscopic data confirmed coordination through the azine nitrogen atoms, yielding metal complexes with a 1:2 metal-to-ligand ratio. Magnetic and electronic spectra supported square-planar coordination in the complexes. Using broth dilution and agar diffusion techniques, we assessed the antibacterial properties of the ligand and its complexes against specific strains of fungi, Gram-positive bacteria, and Gram-negative bacteria. Metal complexation greatly increased the ligand’s biological activity. The Cu(II) complex, which produced the biggest inhibition zones and the lowest minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) values among the synthesised compounds, had the strongest antibacterial action. Increased lipophilicity and improved interaction of the metal complexes with microbial targets after chelation explain the increased activity. These results indicate that the Cu(II) complex is the most promising option for additional biological research and show that coordination of the Schiff base with transition metal ions enhances its antibacterial activity.