Sucrose interaction with alkaline earth metal ions. Synthesis, spectroscopic and structural characterization of sucrose adducts with the Mg(II) and Ca(

Abstract

Crystalline sucrose interacts with hydrous alkaline earth metal ions to give adducts of the type Mg(sucrose)Cl 2.4H 2O, Mg(sucrose) 2Br 2.4H 2O, Ca(sucrose)Cl 2.2H 2O, and Ca(sucrose) 2Br 2.2H 2O. These adducts are characterized by means of elemental analysis, FT-IR spectroscopy. X-ray powder diffraction, and molar conductivity measurements. Due to the marked spectral similarities with those of the structurally known Na(sucrose)Br.2H 2O and other Na-sucrose adducts in the 1:1 metal sugar compounds, the Mg(II) ion is possibly six-coordinate, binding to two sucrose molecules via O(4), O(6) of the first sugar and O(6') of the second molecule and to three H 2O, whereas in the 1:2 metal-sugar adducts, magnesium ion binds to two sugar molecules through O(4), O(6) and to two H 2O, resulting in a six-coordination geometry around the Mg(II) ion. The Ca(II) ion is possibly seven-coordinate in the 1:1 metal-sugar compound, binding to two sucrose molecules through O(4), O(6) of the first and O(6') of the second sugar and to two H 2O molecules as well as to two halide anions, while in the 1:2 metal-sugar adduct it could be bonded to four sugar molecules via O(4), O(6) of the two and O(6') of the other two molecules and to two H 2O, resulting in an eight-coordination geometry around the Ca(II) ion. Upon metal adduct formation, the strong sugar hydrogen bonding network is rearranged to that of the sucrose-OH ... H 2O ... halide ... OH-sucrose system.