Potentiometric Studies on Binary Complexation of Transition Metals with Vanillic Acid and its Biological importance

Abstract

This study investigates the interaction of vanillic acid with transition metal ions, specifically
focusing on the determination of stepwise proton-ligand and metal-ligand formation constants
through potentiometric titration in aqueous-organic media. These stability constants, evaluated at
varying temperatures and ionic strengths, provide critical insights into the thermodynamic
parameters, such as enthalpy and entropy changes, that govern the chelation process. By
quantifying these thermodynamic signatures, the research elucidates the covalent nature of the
metal-ligand bonding, which serves as a fundamental determinant for the bioactivity of these
transition metal complexes. Furthermore, the computed thermodynamic parameters, including
Gibbs free energy, enthalpy, and entropy, clarify the spontaneity and temperature dependence of
these coordination reactions. The biological evaluation of these complexes indicates that the
vanillic acid derivatives exhibit significant antimicrobial properties, suggesting a direct
correlation between their structural stability and their capacity to inhibit microbial growth.