Microwave-Assisted Synthesis: Characterization and in vitro Biological Screening Effects of Schiff Base Metal Complexes
A. Tiwari
Department of Chemistry, Dr. H. S. Gour University, Sagar (M.P.) 470 003, India.
Rajendra K. Jain
Department of Chemistry, GSCE, Sagar (M.P.) 470 001, India.
A.P. Mishra *
Department of Chemistry, Dr. H. S. Gour University, Sagar (M.P.) 470 003, India.
*Author to whom correspondence should be addressed.
Abstract
Eco-friendly synthesis and green applications are continuously being explored by researchers all over the world. Numerous research studies demonstrated that microwave technology is a sophisticated tool for both synthesis and leading applications of Schiff base compounds. The greener approach is prioritized over the conventional synthesis because of its environment friendly, less energy-consuming, less time-consuming, and less hazardous compounds synthesis with low cost. Microwave-assisted synthesis is a branch of green chemistry. Microwave irradiated reactions offer reduced pollution, low cost, and high yield, together with simplicity in processing and handling. Some new Schiff bases and their Co(II), Ni(II) and Cu(II) complexes formed by the condensation of salicylaldehyde with 2-amino-4-hydroxy-6-methylpyrimidine (SAP) and 2-chloroacetophenone with 2-chloro-4-nitroaniline (CCA) have been synthesized by conventional as well as microwave methods. All the reagents used for the preparation of the Schiff bases were obtained from Sigma Aldrich. Metal salts were purchased from Loba Chemie. The synthesized compounds were spectrochemically characterized by elemental analysis, molar conductance, FT-IR, UV–Vis, Mass spectral analysis, ESR and Powdered-XRD. The complexes are coloured and stable in air. Analytical data revealed that all the complexes exhibited 1:2 (metal:ligand) ratio with 4 or 6 coordination around the metal center. FAB-mass and thermal data show a degradation pattern of the complexes. XRD patterns indicate a crystalline nature for the complexes. The Schiff base and metal complexes show a good activity against the bacteria; E. coli, S. aureus, S. fecalis and fungi A.niger, T. polysporum, C. albicans. The antimicrobial results also indicate that the metal complexes are better antimicrobial agents as compared to the Schiff bases. These observations show that the majority of the complexes are more active than their respective Schiff base ligand. The higher inhibition zone of metal complexes than that of the ligands can be explained on the basis of Overtone’s concept and the Chelation theory. The findings of the bactericidal and fungicidal investigation of the compounds against the opportunistic pathogens reveal that the synthesized compounds have antipathogenic activity.
Keywords: Microwave synthesis, 2-amino-4-hydroxy-6-methylpyrimidine, thermal analyses, biological activity