The complexation of metal cations by d-galacturonic acid: a spectroscopic study

• Published in: Carbohydrate research Vol. 339; no. 14; pp. 2391 - 2405
• Main Authors: Synytsya, Andriy, Urbanová, Marie, Setnička, Vladimír, Tkadlecová, Marcela, Havlíček, Jaroslav, Raich, Ivan, Matějka, Pavel, Synytsya, Alla, Čopı́ková, Jana, Volka, Karel
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 04.10.2004
• Subjects: 1H and 13C NMR spectroscopy; Cations, Divalent - chemistry; Electronic spectroscopy; FT-IR and Raman spectroscopy; Galacturonic acid; Hexuronic Acids - chemistry; Magnetic Resonance Spectroscopy; Metal complexes; Metals, Heavy - chemistry; Molecular Structure; Solutions; Vibrational circular dichroism; 1H and 13C NMR spectroscopy; FT-IR and Raman spectroscopy; Galacturonic acid; Electronic spectroscopy; Metal complexes; Vibrational circular dichroism
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2004.07.008

M 2 + + OH - → M ( OH ) 2 ↓ n GalA + M ( OH ) 2 → M · ( GalA ) n M = Cu 2+, Co 2+, Ni 2+, VO 2+; n = 2 for Cu 2+, Co 2+, Ni 2+ and n = 1 for VO 2+. 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 α- and β-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 D 2O 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 D 2O and Me 2SO- d 6 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.