Analysis of Equilibrium and Kinetics of Chromium-Fluoride Complexation from Spectroscopic Data via Chemometrics Methods1

The complexation of Cr3+ with F− undergoes a multistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L(metal to ligand) and 50 °C, the result of Principal Component Analysis (PCA) shows that three complexes, ML, ML2 and ML3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis (TTFA). Meanwhile, a reactive intermediate was observed before the formation of ML, during the specific kinetic study at 15 °C. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.