Metal Ion Interactions with Sugars: Crystal Structure and FT-IR Study of the EuCl3-Ribose Complex

Abstract

A single-crystal of EuCl3·C5H10O5·5H2O was obtained from methanol-water solution and its structure determined by x-ray analysis. Two configurations of the complex, as a pair of anomers, were found in the single crystal in a disordered state, which is different from that reported previously.[ 16 , 17 ] The ligand of one of the isomers is α-D-ribopyranose in the 4C1 conformation, and the ligand of the other is β-D-ribopyranose in the 1C4 conformation. The α:β anomeric ratio is 52:48. Both ligands of the two isomers provide three hydroxyl groups in ax-eq-ax orientation for coordination. The Eu3+ ion is nine-coordinated with five Eu-O bonds from water molecules, three Eu-O bonds from hydroxyl groups of the D-ribopyranose, and one Eu-Cl bond from chloride ion. The hydroxyl groups, water molecules, and chloride ions form an extensive hydrogen-bond network. The IR spectral C-C,O-H,C-O and C-O-H vibrations were observed to be shifted in the complex and the IR results are in accord with those of x-ray diffraction.