Metal-ion interactions with sugars.Crystal structure and FT-IR study of PrCl_3-D-ribose complex

摘要

A single-crystal of PrCl_3 centre dot D-ribose centre dot 5H_2O was obtained from a methanol-water solution and its structure determined by X-ray crystallography.Two configurations of the complex,as a pair of isomers,were found in the single-crystal in a disordered state,which differs from that reported previously.The ligand of one of the complexes is alpha-D-ribopyranose in the ~4C_1 conformation,and the ligand of the other is beta-D-ribopyranose in the ~1C_4 conformation.The alpha:beta anomeric ratio is 54:46.Both ligands of the two isomers provide three hydroxyl groups in an axial-equatorial-axial orientation for coordination.The Pr~(3+) ion is nine-coordinated,with five Pr-O bonds from water molecules,three Pr-O bonds from the hydroxyl groups of the D-ribopyranose and one Pr-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 are shifted in the complex,compared to those in D-ribose,and the IR results are in accord with those obtained from the X-ray diffraction study.