Solvatochromic Effect Studies on the Stability of Dioxovanadium(V) Complexes with Ethylene Glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic Acid in Different Water + Methanol Mixtures

Abstract

The stability constants for the reaction of dioxovanadium(V) with ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′tetraacetic acid (EGTA) and the dissociation constants of EGTA were determined at 25 °C and a constant ionic strength of 0.05 mol • dm -3 sodium perchlorate in ten different compositions of water + methanol by a combination of potentiometric and UV spectrophotometric methods. The Solver, Microsoft Excel 2000 optimization package, has been used to perform nonlinear least-squares curve fitting on the basis of the Gauss-Newton method for calculation of the solvatochromic regression coefficients. Nonspecific and specific solute-solvent interactions were interpreted by correlating the equilibrium data with solvent parameters using the Kamlet-Abboud-Taft (KAT) solvatochromic equation. Finally, the influence of the solvent on the stability of the complex was discussed on the basis of the correlation results and the contribution of R (hydrogen-bond donor acidity), β (hydrogen-bond acceptor basicity), and π* (dipolarity/polarizability) parameters.

Calculation of the stability constants for the complex formation of dioxovanadium (V) with methyliminodiacetic acid in various H2O + CH3OH solutions using kamlet-abboud-taft equation

“…The antitumoral effects of vanadium can be evaluated by the determination of different parameters, such as cell proliferation, morphology and disruption of cellular architecture. [6][7][8] EXPERIMENTAL MIDA, 99 % ( Fig. 3 Vanadium plays a catalytic role in metalloenzyme systems, such as nitrogenase and haloperoxi-dases.…”

“…6 Literature survey shows the glass electrode calibration for various methanol mixtures. 6 Literature survey shows the glass electrode calibration for various methanol mixtures.…”

“…6 The value of 0 H μ is only dependent on the solvent composition. 6 The value of 0 H μ is only dependent on the solvent composition.…”

“…6 The value of 0 H μ is only dependent on the solvent composition. 6 Three titrations have been performed for each volume fraction of methanol and approximately 200 points were used in the calculations at each volume fraction of methanol. 6 Three titrations have been performed for each volume fraction of methanol and approximately 200 points were used in the calculations at each volume fraction of methanol.…”

“…6,10 All experiments were repeated three times, and the average values of experimental dissociation and stability constants along with their deviations from the average are given. Thus, 50 ml acidic solutions of dioxovanadium(V) (5.0×10 -4 mol dm -3 ) were titrated with basic solutions of MIDA (2.0×10 -2 mol dm -3 ) at different volume fractions of methanol.…”