Transition-metal-saccharide chemistry: synthesis and characterisation of D-galactose, D-fructose, D-glucose, D-xylose, D-ribose, and maltose complexes of Mn(II)

Monosaccharide (D-Gal, D-Fru, D-Glc, D-Xyl, D-Rib) and disaccharide (D-Mal) complexes of Mn(II) were synthesised from non-aqueous solutions using [NEt4]2[MnCl2Br2] and MnCl2 · 4H2O. The isolated and purified complexes were characterised by diffuse reflectance, FTIR, EPR, DTA, TGA, magnetic susceptibility, and cyclic voltammetry techniques. Synthesis from [NEt4]2[MnCl2Br2] yielded dimeric complexes 1–3 and 9, and from MnCl2 · 4H2O it yielded trimeric complexes 4–8. These water-soluble complexes were found to be anionic with a Mn-to-saccharide ratio of 1:1 for monosaccharide complexes 1–8 and 2:1 for disaccharide complex 9. The complexes were found to be hydrolytically stable in solution at higher concentrations (⩾ 4 mM), as studied by cyclic voltammetry.