Hydrolysis of the oxovanadium(IV) ion and the stability of its complexes with the 1,2-dihydroxybenzenato(2–) ion

Abstract

A technique which eliminates effects of changes in asymmetry potential has been adapted for use in pH titrations with high-resistance glass electrodes. A study, using cells without liquid junctions, has been made of the hydrolysis of the oxovanadium( iv) ion and of its complexes with the ' I ,2-dihydroxybenzenato(2-) ion. Equilibrium constants University, Whiteknights, Reading RG6 2AD are reported.THE oxovanadium(1v) ion, V02+, forms stable complexes with the 1,2-dihydroxybenzenat0(2 -) ion in aqueous solutions, but the results of earlier quantitative studies of the stabilities, and even the identities, of these complexes are discrepant and unsatisfactory. Potentiometric studies 1-3 were made on cells with liquid junctions and with uncertain control of ionic activity coefficients. Furthermore, the effects of hydrolysis of the oxovanadium(rv) ion or the formation of complexes with sulphate or chloride ions were ignored or inadequately considered. Spectrophotometric measurements lead to stabilityconstant values which disagree with those reported from potentiometric measurements.In the present study precise potentiometric measurements have been made on cells with glass and silversilver chloride electrodes which avoid liquid junctions. A careful examination of the hydrolysis of the oxovanadium(1v) ion was necessary before the investigation of the complexes. The only satisfactory previous study 5 of this hydrolysis relates to measurements in S~-sodium

Coordinating Properties of Pyrone and Pyridinone Derivatives, Tropolone and Catechol toward the VO2+ Ion: An Experimental and Computational Approach

“…The number of experimental points used in the calculations was 150-200 for each system and the reproducibility of the points included in the evaluation was within 0.005 pH unit in the whole pH range measured. 2+ (log β = -6.95), with stability constants calculated from the data of Henry et al [54] and corrected for the different ionic strengths by use of the Davies equation, [54] [VO(OH) 3 ] -(log β = -18.0) and [(VO) 2 (OH) 5 ] -(log β = -22.0). …”

Binding of Oxovanadium(IV) to Dipeptides Containing Histidine and Cysteine Residues

“…Hydroxo complexes of VO 2+ were taken into account in the calculations. The following species were assumed: [VO(OH)] + (log β 1-1 = -5.94), [(VO) 2 (OH) 2 ] 2+ (log β 2-2 = -6.95), and the stability constants were calculated from the data of Henry et al [54] and corrected for the different ionic strengths by use of the Davies equation, [55] [VO-(OH) 3 ] -(log β 1-3 = -18.0) and [(VO) 2 (OH) 5 ] -(log β 2-5 = -22.0). [56] Spectroscopic and Analytical Measurements: Anisotropic EPR spectra were recorded on aqueous solutions with an X-band (9.15 GHz) Varian E-9 spectrometer in the temperature range 120-140 K. As usual for low temperature measurements, a few drops of DMSO were added to the samples to ensure good glass formation.…”

N,N′‐Ethylenebis(pyridoxylideneiminato) and N,N′‐Ethylenebis(pyridoxylaminato): Synthesis, Characterization, Potentiometric, Spectroscopic, and DFT Studies of Their Vanadium(IV) and Vanadium(V) Complexes

“…[71,85,86] For the V v systems the stability constants were similarly defined, where M refers to VO 2 + , not as HVO 4 2À as is most usual in the literature. The speciation of vanadate into monomeric, dimeric, tetrameric, pentameric, and decameric species [87] was taken into account (see SI-11 in the Supporting Information).…”