Complexation of Dioxovanadium(V) with D-(-)-Quinic Acid at Different Ionic Strengths Using Different Models Based on the Debye-Huckel Theory

The complex formation reaction between the dioxovanadium(V) cation and D-(-)-quinic acid {(1R,3R,4S,5R)-(-)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid} has been studied in aqueous solutions. The UV data and the values of the derived conditional stability constants are presented and discussed in the light of one stoichiometric model for the reaction at T=298 K and different ionic strengths (0.10 to 1.00) mola <...dm(-3) of sodium chloride. Speciation diagrams and dissociation constants were obtained on the basis of UV spectroscopic measurements and potentiometric titrations, respectively. Our results show that one complex species, VO2L, exists in solution in the pH range of about 1.00 to 3.00. The parabolic, Specific Ion Interaction Theory (SIT), and extended Debye-Huckel type (EDH) models successfully describe the ionic strength dependence of the stability constants. A comparison with literature data is also reported.