Self-assembly of a 2-D barium/thiodiacetate coordination polymer in aqueous solution

A polymeric thiodiacetate (tda) complex of Ba2+, {Ba[S(CH2COO)(2)(H2O)(3)] center dot 2H(2)O}(n), has been synthesized from aqueous solution in similar to 50% yield. The complex crystallizes in the monoclinic P2(1)/c space group with Z = 4 and the unit cell dimensions a = 13.069 angstrom, b = 7.350 angstrom, and c = 12.932 angstrom. Ba2+ is ten-coordinate, ligated to four tda (O and S) and three aqua ligands. Four distinct binding modes of tda to barium are observed. Each Ba2+ center is coordinated via a tda ligand to four equivalent adjacent Ba2+ centers, creating an extended 2-D polymeric layered structure, with alternate interstitial layers of water. The complex has also been characterized by elemental analysis, FT-IR spectroscopy, and thermogravimetric analysis. H-1 and C-13 NMR spectroscopic data suggest that the polymeric structure found in the solid state is not present in aqueous solution itself.