Sodium dirubidium citrate, NaRb2C6H5O7, and sodium dirubidium citrate dihydrate, NaRb2C6H5O7(H2O)2

Abstract

The crystal structures of sodium dirubidium citrate {poly[μ-citrato-dirubidium(I)sodium(I)], [NaRb2(C6H5O7)] n } and sodium dirubidium citrate dihydrate {poly[diaqua(μ-citrato)dirubidium(I)sodium(I)], [NaRb2(C6H5O7)(H2O)2] n } have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. Both structures contain Na chains and Rb layers, which link to form different three-dimensional frameworks. In each structure, the citrate triply chelates to the Na+ cation. Each citrate also chelates to Rb+ cations. In the dihydrate structure, the water molecules are bonded to the Rb+ cations; the Na+ cation is coordinated only to citrate O atoms. Both structures contain an intramolecular O—H...O hydrogen bond between the hydroxy group and one of the terminal carboxylate groups. In the structure of the dihydrate, each hydrogen atom of the water molecules participates in a hydrogen bond to an ionized carboxylate group.