The complexation of metal cations by D-galacturonic acid: a spectroscopic study |
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Authors: | Synytsya Andriy Urbanová Marie Setnicka Vladimír Tkadlecová Marcela Havlícek Jaroslav Raich Ivan Matejka Pavel Synytsya Alla Copiková Jana Volka Karel |
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Institution: | Department of Carbohydrate Chemistry and Technology, Institute of Chemical Technology, Technická 3/5, 166 28 Prague 6, Czech Republic. sinicaa@vscht.cz |
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Abstract: | Solid complexes of D-galacturonic acid (GalA) with cobalt(II), copper(II), nickel(II) and oxovanadium(IV) (1-4) were prepared and characterised. The metal-to-ligand molar ratio was 1:2 for complexes 1-3 and 1:1 for complex 4. The alpha- and beta-anomers of GalA were detected in all the complexes in solid state and in solutions. An addition of small amounts of the paramagnetic complexes to the D2O solution of pure ligand led to NMR line broadening of some 1H and 13C nuclei. This broadening was sensitive to the anomeric state of GalA in the case of complexes 1 and 4. NMR and vibrational spectroscopic data indicate the formation of carboxylate complexes of all the cations, while noncarboxylic oxygens are also involved into the metal bonding in some cases. VCD spectra of complexes 1-4 in D2O and Me2SO-d6 solutions confirm that GalA carboxylic group may participate in the formation of optically active species around the metal cation. Possible ways of GalA coordination by metal cations of this study were proposed and discussed. |
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Keywords: | Galacturonic acid Metal complexes Electronic spectroscopy 1H and 13C NMR spectroscopy FT-IR and Raman spectroscopy Vibrational circular dichroism |
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