Synthesis and characterization of nickel(II) complexes containing ligands derived from disaccharides and 1,3-diaminopropane

Abstract

The reaction of [Ni(tn)3]2+ ions (tn = 1,3-diaminopropane) with disaccharides having a glucose reducing terminal, i.e. maltose, lactose, cellobiose, and melibiose, in the presence of a catalytic amount of ammonium chloride gave blue, paramagnetic bis(N-D-aldosylpropane-1,3-diamine)nickel(II) complexes. The complexes were characterized by elemental analysis, magnetic susceptibilities, electronic absorption and circular dichroism spectroscopies, X-ray absorption and crystallographic analyses. The complex bis[N-(4-O-α-D-glucopyranosylglucosyl)propane-1,3-diamine]nickel(II) bromide dihydrate crystallizes in the hexagonal space group P6422, with a= 22.125(8), c= 21.464(9)A, and Z= 6. The structure was solved by Patterson methods and refined by full-matrix least-squares techniques to R= 0.080 and R′= 0.094. The complex cation has C2 symmetry and the central nickel atom is octahedrally co-ordinated by two tridentate glycosylamine ligands formed from maltose and tn. Each ligand is bonded through the oxygen atom of the hydroxyl group at C2 of maltose and through the two nitrogen atoms of the diamine in a meridional mode. The co-ordination behaviour of the glucose unit in the octahedral nickel(II) complexes has been established. In the crystal packing, the complex cation exists in a novel dimeric form supported by intermolecular hydrogen bonds, which might provide some fundamental information concerning sugar–sugar interactions in biological systems.