Spectroscopic study of the interactions of alkali fluorides with D-xylose

The interactions of alkali fluorides with D-xylose have been studied by X-r ay diffraction (XRD), infrared spectroscopy (IR), nuclear magnetic resonanc e (NMR, H-1 and C-13) and atomic absorption spectrophotometry. KF and CsF f orm complexes with D-Xylose in a 1:1 molar ratio. These complexes can be ob tained by solid state milling the reactants in an agate mortar or from meth anolic solutions of the sugar and the salt. LiF and NaF do not form complex with D-xylose. IR and XRD prove the identical nature of the complexes obta ined by milling and from solution. IR spectra indicate strong perturbation of the OH stretching vibrations with considerable shifts to lower frequenci es, which must be caused by strong hydrogen bond formation to the fluorine anion. The perturbations of C-O bond are weak, indicating that cation bindi ng to the oxygen atoms is not the main interaction responsible for the comp lex formation. H-1 NMR spectra of the D-Xylose-KF complex dissolved in deut erium oxide is equal to that of pure D-xylose, indicating the destruction o f the complex in solution. The complex is stable in DMSO, and C-13 spectra of the complex in DMSO-d(6) and in solid state (CPMAS) spectra are in accor dance with the observed interactions in the IR spectra. As far as we know, this is the first report of a sugar-halide salt complex in which the anion instead of the cation provides the binding forces. (C) 2001 Elsevier Scienc e B.V. All rights reserved.