Synthesis, spectral characterization, quantum chemical calculations, thermal studies and biological screening of nitrogen and oxygen donor atoms containing Azo-dye Cu(II), Ni(II) and Co(II) complexes

Abstract

Present research work focuses on the synthesis of novel azo-dye Cu(II), Ni(II) and Co(II) chelates of Schiff base based ligand having antimicrobial activities. Azo-dye Cu(II) and Zn(II) complexes derived 7-benzyl-4-(phenyldiazenyl)quinolin-8-ol (HBPDQ) was obtained and described by spectroscopic tools and TGA analysis. UV-visible, IR, 1H, 13C & 15N NMR spectra revealed that the HBPDQ uses its quinoline nitrogen ring and deprotonated hydroxyl group in coordination with Cu(II), Ni(II) and Co(II) ions. The Cu(II), Ni(II) and Co(II) chelates were predicted to be not electrolytic from the measured molar conductance values. Thermal properties and decomposition kinetics of the metal chelates are investigated using Coats-Redfern method. Magnetic susceptibility and electronic spectral data as well as quantum chemical calculations reveal the Cu(II), Ni(II) and Co(II) complexes are octahedral geometry. DFT studies revealed that geometries of metal complexes and azo-dye (HBPDQ) were entirely optimized in relation to use energy by 6-31+g (d,p) basis set. The kinetic parameters like activation energy (E*), pre-exponential factor (A) and entropy of activation (ΔS*) were quantified. Results of spectral studies of mass and TGA data confirmed the octahedral geometry for all chelates. The Cu(II), Ni(II) and Co(II) chelates were investigated for biological action against pathogenic fungi (C. krusei, C. albican) and bacteria (S. aureus, E. coli). The antimicrobial results confirmed that Cu(II), Ni(II) and Co(II) chelates possessed superior inhibition potential than the parent ligand (HBPDQ). The enhanced antimicrobial activity might be due to the chelation.