US EPA

1577430 

Journal Article 

The interaction of D-galactonic acid with Cr-VI and Cr-III. Structure, stability and physical properties of Cr-III-aldonate complexes 

Signorella, S; Santoro, M; Frutos, A; Escandar, G; Salas-Peregrin, JM; Moreno, V; Gonzalez-Sierra, M; Sala, LF 

1999 

Yes 

Journal of Inorganic Biochemistry
ISSN: 0162-0134
EISSN: 1873-3344 

73 

1-2 

93-100 

WOS:000079589800011 

The redox reaction between D-galactonic acid and potassium
chromate yields {((lyxonateH(-1)) (galactonateH(-1)) Cr(OH2))K . H2O}(n), with both aldonate
molecules acting as bidentate ligands with the carboxylate and one alkoxo function as the donor
sites. The shift of the CO2- stretching vibration towards lower frequencies upon coordination and
the high value of av indicate that the carboxylate acts as a monodentate donor site. Magnetic
susceptibility data for the compound in the temperature range 3-300 K exhibit a drop in the
effective magnetic moment with temperature below 70 K, which is indicative of antiferromagnetic
interactions between the Cr-III centres. The molar magnetic susceptibility versus temperature
plot could be fitted with the Fisher Hamiltonian for the case of infinite chains, equation-
modified for the presence of monomeric species. The EPR and W-Vis spectroscopic studies reveal
that, in solution, the complex retains the distorted octahedral local coordination geometry. The
{((lyxonateH(-1))(galactonateH(-1))Cr(OH2))K}(n) dissociates slowly in aqueous solution but
faster at high [H+], because of the rapid protonation of the alkoxo bridges linking the monomeric
units. The potentiometric evaluation of the closely related binary system Cr-III-D-galactonate
shows that the (Cr(galactonateH(-n))(2))(1-2n) complexes are the major species in the 4-12 pH
range, when a 1:2 Cr-III:ligand ratio is used. C-13 NMR reveals that the CO2- group is one of the
coordination sites of the ligand. (C) 1999 Elsevier Science Inc. All rights reserved. 

galactonate; chromium(III)-aldonate complexes; stability; structures