N-(2-Hydroxyethyl)ethylenediamine-N,N’,N’-triacetic acid (HEDTA) is a strong chelator similar to ethylenediaminetetraacetic acid (EDTA) which is commonly used for metal-ion removal. Because of the asymmetry in the HEDTA ligand, more than one coordination complex can form with vanadium (V). The interaction between HEDTA and vanadate has been studied by 1D and 2D, and 51V, 13C, and 1H NMR spectroscopies at ambient temperature to determine the complexes that form in solution and to explore the pH dependence on complex formation. Two main complexes form in the reaction between vanadate and HEDTA at a one to one ratio in the pH range between 3-11. The first complex, V-HEDTA1, begins to form at pH 6 and decreases as pH increases to pH 11. The second complex, V-HEDTA2, forms above pH 3 and increases with pH increase until above pH 9 where it no longer forms. Structurally, V-HEDTA2 is similar to the complex that forms between vanadate and EDTA, although the data is consistent with the alkoxy arm of the V-HEDTA2 complex also being weakly coordinated to the metal atom. The other complex, V-HEDTA1, include in the coordination the alkoxy group. The formation constants and the b values of both V-HEDTA complexes were calculated for the future use for speciation considerations in biological and environmental studies.

Multinuclear 51V NMR studies of aqueous vanadium-HEDTA complexes

251st National Meeting (2016)

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