ABSTRACT
This study presents the coordination modes and crystal organization of a calcium-potassium coordination polymer, poly[hexaaquabis(mu4-4-carboxybenzenesulfonato-kappa4O1:O1':O1'':O4)bis(mu3-4-carboxybenzenesulfonato-kappa2O1:O1')calcium(II)dipotassium(I)], [CaK2(C7H5O5S)4(H2O)6]n, displaying a novel two-dimensional framework. The potassium ion is seven-coordinated by four sulfonate and one carboxyl O atom located on five different acid ligands, two of which are unique, and by two symmetry-independent water O atoms. A pair of close potassium ions share two inversion-related sulfonate O-atom sites to form a dimeric K2O12 unit, which is extended into a one-dimensional array along the a-axis direction. The six-coordinate Ca2+ ion occupies a special position (1) at (0, 1/2, 1/2) and is surrounded by four sulfonate O atoms from two inversion-related pairs of unique acid monoanions and by two O atoms from aqua ligands. The compound displays a layered structure, with K2O12 and CaO6 polyhedra in the layers and aromatic linkers between the layers. The three-dimensional scaffold is open, with nano-sized channels along the c axis.
ABSTRACT
This study presents the coordination modes and two-dimensional network of a novel strontium(II) coordination polymer, [Sr(C(7)H(5)O(5)S)(2)(H(2)O)(3)](n). The eight-coordinate Sr(2+) ion is in a distorted bis-disphenoidal coordination environment, surrounded by four sulfonate and one carboxyl O atom from five benzenesulfonate ligands, two of which are symmetry unique, and by three O atoms from three independent aqua ligands. The compound exhibits a monolayer structure with coordination bonds within and hydrogen bonds between the layers. The mu(4) acid ligand bridges the metal ions in two dimensions to form a thick undulating monolayer with a hydrophobic interior and hydrophilic surfaces. A second independent monoanion is arranged outward from both sides of the monolayer and serves to link adjacent monolayers via carboxyl-water and water-carboxyl hydrogen bonds.
ABSTRACT
The crystal structure of the title compound, C(12)H(12)O(6)P(2), displays two different regions alternating along the a axis: a hydrogen-bonded region encompassing the end-positioned phosphonic acid groups and a hydrophobic region formed by the aromatic spacers. The asymmetric unit contains only half of the biphenyl-4,4'-diphosphonic acid (4,4'-bpdp) molecule, which is symmetric with an inversion centre imposed at the mid-point between the two aromatic rings. The periodic organization of the molecules is controlled by two strong O-H...O interactions between the phosphonic acid sites. Weak C-H...pi interactions are established in the aromatic regions.
