Structure determination of a twinned Rb(H2NC10H6SO3) center dot H2O crystal and comparison to related alkali metal aminonaphthalenesulfonates

Rb(H2NC10H6SO3) . H2O crystallizes in space group P2(1) with two formula un its in the asymmetric unit, the crystal being twinned by a 180 degrees rota tion about [1 0 0]. The structure was determined from X-ray diffraction dat a, and refined, based on two twin components, to yield a final R value of 0 .0557 for 2754 reflections. The structure consists of alternating layers of aminonaphthalenesulfonate and rubidium ions. There are two distinct rubidi um environments, the metal ions linked by the sulfonate groups and bridging water molecules into an infinite sheet. The sulfonate groups are bidentate , monodentate and bridging, all oxygen atoms being bound to at least one me tal. The amino groups do not participate in coordination to the metal. Arom atic moieties from neighboring hydrophile metallo-layers interleave to form the hydrophobic layers. There is some similarity to the analogous sodium a nd potassium structures, however the rubidium compound is distinguished by an infinite cationic layer, rather than columns observed for the other two structures.