Quantitative Determination of Metal–Ligand Stability Constants by UV–Visible Spectrophotometry

Abstract

The quantitative determination of metal–ligand stability constants is essential for understanding the thermodynamic and structural aspects of coordination complexes in solution. This study employs UV–Visible spectrophotometry as a reliable and sensitive technique to evaluate the formation and stability of metal–ligand systems. The method is based on monitoring changes in absorbance associated with electronic transitions that occur upon complex formation, including shifts in maximum absorption wavelength (λmax), new absorption bands and variations in intensity. Experimental measurements were conducted under controlled conditions of concentration, solvent composition and temperature to ensure reproducibility and adherence to the Beer–Lambert law. Stability constants were determined by analysing absorbance data obtained at selected wavelengths using established methods such as the mole ratio method and continuous variation approach. The results demonstrated clear spectral distinctions between free species and complexes, confirming successful coordination and enabling accurate calculation of equilibrium constants. The study highlights the effectiveness of UV–Visible spectrophotometry in providing both qualitative and quantitative insights into metal–ligand interactions. The findings contribute to a deeper understanding of coordination behaviour, with implications for applications in analytical, environmental and bioinorganic chemistry.