Liquid-assisted Mechanochemical Synthesis: Green Approach to Synthesis of Co(II) Schiff Base Complex and of Evaluation of Antimicrobial Activities

Abstract

The use of liquid-assisted grinding to bring about reaction between solids, can offer lower-west paths to chemical product by avoiding bulk solvent during reaction. The schiff base ligand derived from 2-hydroxy-1-napthaldehyde and 1,2-phenylenediamine namely 2,2^'-[1,2-Phenylenebis(nitrilomethylidyne)] bis-naphthol; [H₂(L)] and its corresponding Co(II) complex were synthesized using liquid assisted mechanochemical grinding method and characterized by means of IR spectroscopy, powder X-ray diffraction, differential scanning calorimetry, Thermogravitric analysis, energy dispersive X-ray and CHN analysis. The schiff base have been found by a conventional solution method for comparison. In the complex compound, the coordination environment around metal centre consist of two Nitrogen and two oxygen atoms of the schiff base ligand which forms square planar geometry. Evidence from Infrared spectral study indicated a strong band in the spectra of free ligand occurring at 1641cm^-1 which assigned to ν(C=N). It shifted to lower frequency region 1625cm^-1 in the complex indicating the involvement of nitrogen atom of azomethine group. The coordination of Schiff base with the metal ion as showed by the appearance of low frequency band at 452cm^-1 due to metal-oxygen ν(M-O) vibration thus confirming participation of oxygen in the coordination. Further coordination of metal to azomethine nitrogen ν(M-N) is confirmed by a new band at 753cm^-1. The PXRD reveals that, the patterns of the ground mixture were entirely different from the starting constituents, indicating that all the starting materials were transformed to product furthermore the melting point/decomposition temperature and colour of the complexes were different from that of the schiff base indicating the formation of coordination compounds. The synthesized schiff base ligand, and metal complex were screened for its antibacterial activity using gram positive (Staphylococcus aurous) and gram negative (Escherichia coli) and antifungal activity using Aspergillum flavus. (gram positive)and Aspergillus niger. (gram negative)as potential antimicrobials and showed moderate activity.