STRUCTURAL-PROPERTIES OF SILVER(I) AND MERCURY(II) COMPLEXES OF D-LACTOBIONATE - SELF-ASSEMBLED COORDINATION POLYMERS

Single crystals of silver(I) and mercury(II) D-lactobionates (LBA) gro wn from aqueous solutions were subjected to X-ray analysis. Both compo unds crystallize in the monoclinic space group C2 (No. 5) with unit ce ll dimensions a = 29.621(5) Angstrom, b = 7.392(2) Angstrom, c = 7.430 (2) Angstrom, and beta = 90.75(2)degrees for Ag[LBA]. H2O and a = 29.0 84(3) Angstrom, b = 7.4066(11) Angstrom, c = 7.4761(9) Angstrom, and = 90.718(9)degrees for Hg[LBA](2). 2H(2)O, Final solutions of both crys tal structures reveal that both sugar acid-metal complexes form novel metal-bridged polysaccharides having similar structures achieved by co ordination of alcoholic oxygens O(3) and O(6') in LBA to the metals, a lthough both complexes have different local geometries around metal io ns: distorted trigonal bipyramidal for Ag[LBA]. H2O and octahedral for Hg[LBA](2). 2H(2)O. Intermolecular interactions were observed through hydrogen bondings of O(4') in the galactosyl unit with O(5) and O(6) in the gluconic acid moieties of the upper polymeric unit, which is pr esumed to be an important factor inducing the formation of polymeric s tructures. In addition, a carbohydrate-carbohydrate interaction was al so observed through hydrogen bondings between O(2') and O(3') of neigh boring galactosyl units. Silver(I) and mercury(II) complexes lose thei r polymeric nature in water in different manners: the silver(I) comple x is fully dissociated, but the mercury(II) complex exists as a monome ric neutral form.