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)Å, 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.