Synthesis, characterization, kinetic, thermodynamic and antimicrobial activity studies of complexes of Cd(II), Cr(III), and Zr(IV) derived from benzaldehyde and ethylenediamine

Abstract

A Schiff base ligand N,N’-Bis(Benzoin)ethylenediimine (B₂ED) obtained from benzaldehyde and ethylenediimine and its Cd(II),Cr(III) and Zr(IV) complexes was synthesized and characterized using electronic spectra (ultra-violet visible spectroscopy), infrared spectra (vibrational spectroscopy), molar conductivity measurement, solubility test and melting point determination. The ligand and the metal complexes were insoluble in the solvents distilled water, hexane, aqueous ammonia, potassium hydroxide and sulphuric acid but soluble in acetone, glacial acetate, DMSO and DMF. The conductance data showed that both the ligand and the metal complexes exhibited weak ionic (non-electrolytic character) while the melting point for ligand and decomposition temperature for complex showed they are fairly stable. The IR spectrum of B₂ED showed characteristic vibrations of C=N and OH groups at 1677 and 3377 cm^-1, respectively. In the spectra of Cd²⁺, Cr³⁺ and Zr⁴⁺ complexes, the azomethine band (V_C=N) was shifted to lower wave number (1630–1634 cm^-1) whereas, the v(OH) is shifted by 18–48 cm-1 to lower frequency upon complex formation suggesting involvement of C=N and OH groups in coordination. The electronic spectra showed that the metal complexes exhibited single, double or triple bands which are consistent with the octahedral and tetrahedral geometry for the metal complexes. The Kinetics of the complex formation were studied by determining the amount of complex formed with time at different temperatures of (25, 35, 45, 55 and 65^oC). The kinetic results showed that increase in time and temperature respectively increased the yield of the complexes. The activation energies of the reactions were in the range of 12.288-18.707 kJ mol⁻¹. The high values of the activation energies reflect the thermal stability of the complexes. The metal complexes exhibited antimicrobial performances, such as low minimum inhibitory concentration (MIC ≤ 250) and bactericidal effect than the ligand. These could become promising antimicrobial agents with potential applications in pharmaceutical industry for controlling the pathogenic bacteria.

Keywords: Antimicrobial studies, kinetics, Schiff base Complexes, thermodynamics