Urease and α-chymotrypsin inhibitory activities of transition metal complexes of new Schiff base ligand: Kinetic and thermodynamic studies of the synthesized complexes using TG–DTA pyrolysis

Abstract

The Schiff base 2-[(E)-(quinolin-3-ylimino)methyl]phenol (H-QMP) was crystallized in Pc space group and complexed with Ni(II) and Co(II) in [M(QMP)2] and Cu(II) and Zn(II) in [M(QMP)(CH3COO)]H2O compositions. Elemental analyses, mass spectrometry, IR, UV–vis spectroscopy, conductance study and magnetic susceptibilities were used to characterize the complexes. The thermograms obtained in the range of 30–1000°C were used for kinetic and thermodynamic calculations. The activation energies and order of pyrolysis were calculated using Horowitz–Metzger method. The calculated activation energies were subsequently used for the calculations of thermodynamic parameters including ΔS*, ΔH* and ΔG*. It was found that the thermal stability and activation energy follow the order Cu(II)>Ni(II)>Co(II)>Zn(II) and ENi*>ECu*>ECo*>EZn*, respectively. All the compounds were also studied for their urease and α-chymotrypsin inhibition, showing medium to moderate activities for both the enzymes except nickel complex. Nickel complex shows IC50=9.9±0.124μM±SEM, and the activity was rationalized by carrying out molecular modeling studies.