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Indirect photometry and multinuclear 13C and 183W NMR study of tungstate complexes of sugar acids: Stabilities and structures

Paper ID Volume ID Publish Year Pages File Format Full-Text
28826 44094 2008 11 PDF Available
Title
Indirect photometry and multinuclear 13C and 183W NMR study of tungstate complexes of sugar acids: Stabilities and structures
Abstract

The tungstate complexes of the sugar acids, meso-tartaric and l-gulonic acids, have been studied in aqueous solutions. Indirect photometry has been used to determine the stability constants and the stoichiometry of these colourless complexes. Multinuclear 13C and 183W NMR spectroscopies have been used to specify the structures of the complexes and the sites of chelation of the ligand. For meso-tartaric acid, complexes of the lactic type with a mononuclear and with a dinuclear tungsten core have been identified. In these type lactic complexes, only the hydroxyl groups of the carboxyl function and the atom carbon in α position belong to the site of chelation of the tungstate complexes. Both α-hydroxyacid moieties of the meso-tartaric acid are involved in the chelation.For l-gulonic acid, lactic type complexes with a mononuclear and a dinuclear tungsten core have been observed at acidic pH. Upon increasing the pH, the lactic complexes disappear: first the mononuclear, then the dinuclear complexes. In pH range 4–8, for gulonic acid, dual lactic, threo (tetradentate) type complexes occur, the dual lactic, erythro and lactic, threo complexes exist. At pH 10, for gulonic acid, a single complex has been identified in which the ligand is pentadentate. In this complex, all carbon atoms of the ligand are involved in the site of chelation except the carboxyl atom.

Keywords
Tungstate complexes; Indirect photometry; Multinuclear 13C and 183W NMR; Site of chelation; Lactic type complexes; Erythro and threo type complexes
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Indirect photometry and multinuclear 13C and 183W NMR study of tungstate complexes of sugar acids: Stabilities and structures
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 194, Issue 1, 5 February 2008, Pages 81–91
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us