Multicomponent Polyanions. 36. Hydrolysis and Redox Equilibria of the H(+)--HVO4(2-) System in 0.6 M Na(Cl). A Complementary Potentiometric and 51V NMR Study at Low Vanadium Concentrations in Acid Solution.

The dependence of vanadate phenyl ester formation on the acidity of the parent phenols

“…If and 6h are the limiting chemicalshifts at low and high pH for the monoanion and dianion, respectively, and sobs is the observed average chemical shift, then a simple calculation shows that the pK, of the entity of interest is related to the chemical shifts and the pH by eq. [2].…”

“…Various studies have succeeded in unravelling many of the details of this system (1,2). These studies are of increasing importance as it has become evident from recent work that vanadium has an important biological role both in nitrogen fixation (3,4) and in halogenation reactions (4,5).…”

Fifteen Years of Dancing with Vanadium

“…At that time, the speciation was less understood and the signal now assigned to V 4 , was believed by some to be a trimer because in some concentration ranges the distinction is not readily made [26][27][28]. A combination of spectroscopy and titration did, however, show that the species forming the signal contained four V-atoms [29,30]. Although studies investigating the speciation and simple oxovanadate systems were 51 V NMR of 0.39 mM vanadate in the presence of increasing concentrations of ethanol at pH 7.5 in 50 mM tris-acetate buffer.…”

“…Studies at lower ionic strength began to emerge and demonstrated quantitative differences, but no qualitative differences in the speciation [29,[31][32][33]. Combined potentiometric and NMR studies were particularly powerful in detailing the properties of oxovanadates [29,30], which were critical for the studies that explored the reactions of vanadium(V) in the physiological relevant pH range. Such studies were carried out by the Tracey/Gresser group [20][21][22], the Crans group [34][35][36], the Rehder group [23,37,38], and others [39][40][41].…”

“…Finally, the isolation of vanadate from a Sigma preparation of ATP was found to be a very potent inhibitor of the (Na,K)-ATPase enzyme [147] fueled a great deal of interest in the vanadiumphosphorus analogy. Although the existence of the oligomeric oxovanadates had been reported [18,29,30,42], the possibility that the various forms of vanadium-compounds could have different biological effects had not been realized. Over a 10-year period, key discoveries were made which shaped our current thinking and understanding of the effects of vanadium compounds.…”