The characterization of primary, secondary, and tertiary vanadate alkyl esters by <sup>51</sup>V nuclear magnetic resonance spectroscopy

Tracey, Alan S.; Gresser, Michael J.

doi:10.1139/v88-403

Cited by 35 publications

(8 citation statements)

References 20 publications

(34 reference statements)

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“…8 A substantial fraction of V¡ in 81% ¡er¡-butyl alcohol and 5 mM KOH (about 20% of the total) is expected to be present as the dianion ester on the basis of equilibrium constants reported for a 10% solution . However, only one 51V NMR resonance was observed under these conditions, and that resonance was substantially closer to the chemical shift of HOV032" than that reported for tert-Bu0V032" (Tracey & Gresser, 1988a). Even at 94% fert-butyl alcohol (4 mM KOH/50 mM I8-crown-6 ether), only a single NMR resonance was observed.…”

Section: Resultssupporting

confidence: 46%

“…Since frequent reference is made herein to crystal field theory, which deals with geometrically disposed charge-charge interaction, we refer to groups attached to vanadium as "ligands of V(V)", while retaining the former structural representation, because of its analogy with phosphate chemistry. 7 The possibility that geometrical changes are produced in the ligand sphere of vanadate mono-or ¿¡anions by substitution of bulky RO" ligands for the HO" ligand is unattractive in view of the observation that successive substitution of CH3 groups for methyl hydrogens of CH3OV-03H", (CH30)2V02", or CH30V032" produces incremental changes in the respective 51V NMR chemical shifts that are similar in magnitude [except in the case of (¡-Bu0)2V02", where the chemical shift was measured in a different solvent system (Tracey & Gresser, 1988a)].…”

Section: Resultsmentioning

confidence: 99%

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Study of the oxyvanadium constellation in transition-state-analog complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

Ray

Post²

1990

Biochemistry

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The absorbance peak in the near ultraviolet electron-transfer spectrum of the oxyvanadium constellation in the "transition-state-analogue complexes" obtained by treating the dephospho form of phosphoglucomutase with inorganic vanadate in the presence of either glucose 1-phosphate or glucose 6-phosphate, as described in an accompanying paper [Ray, W. J., Jr., Burgner, J. W., II, & Post, C. B. (1990) Biochemistry (second of four papers in this issue)], is centered at a wavelength of 312 nm. The position of this peak amounts to a change in oscillator frequency of about -5000 cm-1 relative to that of tetrahedral VO4(3-). To provide a rationale for this spectral change, the near ultraviolet spectra of the di- and monoanions of inorganic vanadate and a number of derivatives of these anions are compared with that of vanadium (V) in the enzymic complexes, in terms of both what is observed experimentally and what is expected from crystal field theory. Comparisons in water and in largely anhydrous solvents show that water is not an essential element in the coordination sphere of inorganic vanadate or its mono- or diesters and hence that the coordination number of V(V) in such compounds likely is four. These comparisons also show that loss of solvating water from a 4-coordinate vanadate on binding cannot provide a rationale for the spectra of the enzymic complexes. Other comparisons show that neither the binding of metal ions nor protonation nor the binding of vanadate at a site with an unusually high or an unusually low dielectric constant can provide such a rationale. Further comparisons with vanadates known to be pentacoordinate strongly suggest that the coordination number of V(V) in the transition-state-analogue complexes of phosphoglucomutase does not exceed four. In fact, from the standpoint of crystal field theory the marked red shift observed in the electron-transfer absorbance spectrum of the oxyvanadium constellation in these complexes is more reasonably interpreted in terms of a decreased coordination at vanadium (V), viz., in terms of a weakened bonding between vanadium and one or more of its coordinating oxygens. This decreased coordination could be produced by a physical stretching of the vanadate ester linkage. By contrast, the near ultraviolet spectrum of the transition-state-analogue complex that ribonuclease forms with an adduct of uridine and vanadate [Lindquist, R. N., Lynn, J. L., & Lienhard, G. E. (1973) J. Am. Chem. Soc. 95, 8762] is similar to spectra of pentacoordinate model compounds of vanadium(V).(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Resultssupporting

confidence: 46%

Section: Resultsmentioning

confidence: 99%

Study of the oxyvanadium constellation in transition-state-analog complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

Ray

Post²

1990

Biochemistry

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“…Another contribution to the stability of the current complexes may be that of chelate formation as in 1 or 2 . Crystal structures of hydroxamic acid complexes of vanadate certainly show structures of this type. − Nonetheless, 1,2-diols do not seem to form stronger 1:1 complexes with vanadate than do simple alcohols . The structure of the present complexes is discussed in more detail below.…”

Section: Resultsmentioning

confidence: 81%

Formation and Structure of 1:1 Complexes between Aryl Hydroxamic Acids and Vanadate at Neutral pH

Bell

Pratt

2002

Inorg. Chem.

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Although aryl hydroxamic acids are well-known to form coordination complexes with vanadate (V(V)), the nature of these complexes at neutral pH and submillimolar concentrations, the conditions under which such complexes inhibit various serine amidohydrolases, is not well established. A series of qualitative and quantitative experiments, involving UV/vis, (1)H NMR, and (51)V NMR spectroscopies, established that both 1:1 and 1:2 vanadate/hydroxamate complexes form at pH 7.5, with the former dominating at submillimolar concentrations. Formation constants for the complexes of several aryl and alkyl hydroxamic acids were determined; for example, for benzohydroxamic acid, the stepwise formation constants of the 1:1 and 1:2 complexes were 3000 and 400 M(-1), respectively. The (51)V chemical shift of the 1:1 4-nitrobenzohydroxamic acid complex was -497 ppm, and that of its unsubstituted analogue was -498 ppm. A (1)H-(15)N HSQC spectrum of the 4-nitrobenzo-(15)N-hydroxamic acid/vanadate complex indicated the presence of an N-H group with (15)N and (1)H chemical shifts of 115 and 5.83 ppm, respectively. A (13)C NMR spectrum of the complex of 4-nitrobenzo-(13)C-hydroxamic acid with vanadate displayed a resonance at 170.1 ppm and thus a coordination-induced shift (CIS) of +3.8 ppm. In contrast, the CIS value of an established 1:2 complex, thought to contain chelated hydroxamic acid ligands, was +11.9 ppm. These spectral data led to the following structural picture of 1:1 complexes of vanadate and aryl hydroxamic acids. They contain penta- or hexa-coordinated vanadium. The ligand is in the hydroxamate rather than hydroximate form. The ligand is presumably bound to vanadium through the hydroxamic hydroxyl oxygen, but the hydroxamic acid carbonyl oxygen interacts weakly with vanadium. These species are the most likely candidates for the inhibitors of serine amidohydrolases found in vanadate/hydroxamic acid mixtures.

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“…The vanadate ion spontaneously and reversibly condenses with a variety of molecules containing hydroxyl groups to provide esterified vanadate derivatives (6,7,9,10). This condensation has been shown to be reasonably favourable both for the ions v04H2-and VO4HZp with the individual condensations apparently occumng in the manner indicated in Scheme 1 where 1 refers to the ligand.…”

Section: Resultsmentioning

confidence: 98%

Vanadium(V) oxyanions. The dependence of vanadate alkyl ester formation on the pK_a of the parent alcohols

Tracey¹,

Galeffi²,

Mahjour³

1988

Can. J. Chem.

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The interaction of vanadate (V04H11-) with a variety of alkyl alcohol's (ROH) covering about seven pK, units of acidity have been studied in aqueous solution by ''v nuclear magnetic resonance spectroscopy. A linear free energy relationship between the equilibrium constant for the formation of the vanadate monoester ( H O V O~R '~) and the acidity of the alcohol was established at 23'C. The correlation was found to be log I/K = -(0.09 ? 0 . 0 2 )~~:~~ + 2.1 k 0.3 where. This correlation was shown not to extend to ligands with T-bonding capability such as phenols or phosphates, where the products are highly favoured relative to the alkyl esters. An interesting correlation between pK, values of the product esters and the pK, of the parent alcohols was also observed. It was found that below a p~:OH of about 15 the pK, values of the esters were essentially constant. However, above this value of 15 the pK, of the ester was found to increase rapidly with an increase in pK, of the alcohol. This result may indicate that the electron accepting ability of the metal is exhausted with the higher pK, alcohols, and the extra electron density is transferred to the oxygens, thus causing an increase in pK, of the ester. On a trouvt que la corrilation prend la forme de log 1/K = -(0,09 k 0 , 0 2 )~~:[ROH]. On a dCmontrC que cette corrClation ne s'ttend pas aux ligands prCsentant une capacitt de liaison par des Clectrons T, comme les phCnols ou les phosphates; dans ces cas, les produits sont trks favorisCs par rapport aux esters d'alkyles. On a aussi observC une corrtlation inttressante entre les valeurs des pK, des esters qui se foment comme produits et les pK, des alcools qui leur donnent naissance. On a trouvt qu'en-dessous d'une valeur de 15 pour le p~:OH, les ialeurs des p~, des esters augmentent rapidement avec une augmentation du pK, des alcools. Ce rtsultat semble indiquer que la facilitt du mCtal i accepter des Clectrons est CpuisCe avec les alcools de pK, ClevC et que la densitt Clectronique additionnelle est transferee aux oxygknes; ceci provoque une augmentation du pK, de I'ester.[Traduit par la revue]

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The characterization of primary, secondary, and tertiary vanadate alkyl esters by ⁵¹V nuclear magnetic resonance spectroscopy

Cited by 35 publications

References 20 publications

Study of the oxyvanadium constellation in transition-state-analog complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

Study of the oxyvanadium constellation in transition-state-analog complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

Formation and Structure of 1:1 Complexes between Aryl Hydroxamic Acids and Vanadate at Neutral pH

Vanadium(V) oxyanions. The dependence of vanadate alkyl ester formation on the pK_a of the parent alcohols

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The characterization of primary, secondary, and tertiary vanadate alkyl esters by 51V nuclear magnetic resonance spectroscopy

Cited by 35 publications

References 20 publications

Study of the oxyvanadium constellation in transition-state-analog complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

Study of the oxyvanadium constellation in transition-state-analog complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

Formation and Structure of 1:1 Complexes between Aryl Hydroxamic Acids and Vanadate at Neutral pH

Vanadium(V) oxyanions. The dependence of vanadate alkyl ester formation on the pKa of the parent alcohols

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The characterization of primary, secondary, and tertiary vanadate alkyl esters by ⁵¹V nuclear magnetic resonance spectroscopy

Vanadium(V) oxyanions. The dependence of vanadate alkyl ester formation on the pK_a of the parent alcohols