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VO2+ complexation by bioligands showing keto–enol tautomerism: a potentiometric, spectroscopic, and computational study

Sanna, Daniele and Varnágy, Katalin and Timári, Sarolta and Micera, Giovanni and Garribba, Eugenio (2011) VO2+ complexation by bioligands showing keto–enol tautomerism: a potentiometric, spectroscopic, and computational study. Inorganic Chemistry, Vol. 50 (20), p. 10328-10341. eISSN 1520-510X. Article.

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DOI: 10.1021/ic201392d


The interaction of VO2+ ion with ligands of biological interest that are present in important metabolic pathways—2-oxopropanoic acid (pyruvic acid, pyrH), 3-hydroxy-2-oxopropanoic acid (3-hydroxypyruvic acid, hydpyrH), oxobutanedioic acid (oxalacetic acid, oxalH2), (S)-hydroxybutanedioic acid (l-malic acid, malH2), and 2,3-dihydroxy-(E)-butanedioic acid (dihydroxyfumaric acid, dhfH2)—was described. Their complexing capability was compared with that of similar ligands: 3-hydroxy-2-butanone (hydbut) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, squarH2). All of these ligands (except l-malic acid) exhibit keto–enol tautomerism, and the presence of a metal ion can influence such an equilibrium. The different systems were studied with electron paramagnetic resonance (EPR) and UV–vis spectroscopies and with pH potentiometry. Density functional theory (DFT) methods provide valuable information on the relative energy of the enol and keto forms of the ligands both in the gas phase and in aqueous solution, on the geometry of the complexes, and on EPR and electronic absorption parameters. The results show that most of the ligands behave like α-hydroxycarboxylates, forming mono- and bis-chelated species with (COO, O) coordination, demonstrating that the metal ion is able to stabilize the enolate form of some ligands. With dihydroxyfumaric acid, the formation of a non-oxidovanadium(IV) complex, because of rearrangement of dihydroxyfumaric to dihydroxymaleic acid (dhmH2), can be observed. With 3-hydroxy-2-butanone and 3,4-dihydroxy-3-cyclobutene-1,2-dione, complexation of VO2+ does not take place and the reason for this behavior is explained by chemical considerations and computational calculations.

Item Type:Article
ID Code:6848
Uncontrolled Keywords:VO2+, electron paramagnetic resonance (EPR), pH potentiometry, density functional theory (DFT)
Subjects:Area 03 - Scienze chimiche > CHIM/03 Chimica generale e inorganica
Divisions:001 Università di Sassari > 02 Centri > Centro di eccellenza interdisc. sviluppo ricerca biotecnologica e studio biodiversità della Sardegna e dell'area mediterranea
001 Università di Sassari > 01 Dipartimenti > Chimica
002 Altri enti e centri di ricerca del Nord Sardegna > CNR-Consiglio Nazionale delle Ricerche > Istituto di chimica biomolecolare, Sassari
Publisher:American Chemical Society
Deposited On:19 Dec 2011 09:45

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