Samuel M. F. Lo

Variable-temperature neutron diffraction studies of the short, strong hydrogen bonds in the crystal structure of pyridine-3,5-dicarboxylic acid

Pyridine-3,5-dicarboxylic acid has been studied by single-crystal neutron diffraction at 15 and 296 K. Pyridine-3,5-dicarboxylic acid, in which the carboxylic acid protons have been replaced by deuterons, has also been studied at 15, 150 and 296 K. The protonated structure contains a short N...H...O hydrogen bond [N...O 2.523 (2) Angstrom at 15 K]. Temperature-dependent proton migration occurs where the N--H distance in the hydrogen bond changes from 1.213 (4) Angstrom at 15 K to 1.308 (6) Angstrom at 300 K. In the deuterated structure the overall hydrogen-bond length increased [N...O 2.538 (3) Angstrom at 15 K] and the magnitude of the migration increased so that the N--D distance changes from 1.151 (3) Angstrom at 15 K to 1.457 (4) Angstrom at 300 K.

Hollow spheres based on mesostructured lead titanate with amorphous framework.

Hollow spheres of mesostructured lead titanate, denoted as PTM-1, have been prepared via a combined oil-in-water emulsion mediated and neutral amine supermolecular templated route. The variety of reaction temperatures and KOH concentrations indicates hollow spheres can be formed under a very critical condition. The structure and composition of the as-synthesized PTM-1 have been determined by powder X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), CHN (carbon-hydrogen-nitrogen) elemental analysis, and thermal analysis. Chemical extraction of organic templates by a cosolvent of weak acid and alcohol has resulted in the formation of a new mesoporous material of non-silica oxide with high porosity.

Barium terephthalate, a three-dimensional coordination polymer with 7 : 7 cation-anion connectivity

Barium terephthalate, [Ba{1,4-C6H4(COO)2}]n, forms a three-dimensional coordination network polymer with 7:7 connectivity between the Ba cations and terephthalate dianions. Each Ba is eight-coordinate and uses all eight oxygen lone pairs of the ligand.

Hydrothermal synthesis of [Ba3Cl2] [Sn3O4(OH)(8)], a compound with alternating ionic and covalent layers

Abstract [Ba3Cl2][Sn3O4(OH)8] (1), is formed through hydrothermal synthesis in the BaCl2/SnCl4 system. 1 is orthorhombic, Pnma, a=7.836(2), b=18.350(4), c=10.258(2) A, V=1475 A3 and composed of alternating layers of covalent stannate and ionic barium chloride components. The ‘covalent’ layers consist of hydroxy stannate trimers [Sn3O4(OH)8], connected through μ3-O to other units forming puckered 2-D sheets. These sheets are then intercalated by the barium and chloride ions, which have a complex set of ionic contacts.