Synthesis and Characterization of Bioactive Schiff Base Ligand Derived from 2-hydroxy-1-napthaldehyde and 4-aminobenzonitrile and its Co(II), Ni(II) and Cu(II) Complexes

The Schiff base derived from 2-hydroxy-1-napthaldehyde and 4-aminobenzonitrile and its corresponding Co(II), Ni(II) and Cu(II) complexes were synthesized and characterized by means of FT-IR spectroscopy, thermal analysis, powder x-ray analysis (PXRD), conductivity measurement, magnetic susceptibility  and elemental analysis. The mononuclear complexes have been obtained by liquid-assisted mechanochemical method. The Schiff base was synthesized in high yield > 90% with negligible waste. FT-IR study indicates a strong band in the spectra of the Schiff base at 1577 cm-1 assigned to azomethine v(C=N) stretching vibration which shifted to new frequency regions in the spectra of complexes indicating the formation of the anticipated complexes. The Schiff base melted at 197oC while decomposition temperatures of the complexes were in the range of 265 - 300oC, signifying good thermal stability. Molar conductance values were in the range of 4.39 - 1349 Ω-1cm2mol-1, indicating non electrolytic nature of the synthesized complexes. Magnetic susceptibility measurement showed that Co(II), Ni(II)  and Cu(II) complexes are  paramagnetic and exhibit magnetic moment in the range of 1.50 - 3.19 BM, the values correspond to the tetrahedral geometry. The relative percentage of the constituent elements (C, H, N) obtained from CHN analysis and calculated values using the proposed structures are similar and are in good agreement. The Schiff base and metal complexes were evaluated as agent for inhibiting growth of pathogenic bacteria using disc diffusion method. The results indicated that metal complexes are more active compared to Schiff base ligand against the test organisms.