Sodium dirubidium citrate, NaRbCHO, and sodium dirubidium citrate dihydrate, NaRbCHO(HO).

The crystal structures of sodium dirubidium citrate {poly[μ-citrato-dirubi-dium(I)sodium(I)], [NaRb(CHO)] } and sodium dirubidium citrate dihydrate {poly[di-aqua-(μ-citrato)dirubidium(I)sodium(I)], [NaRb(CHO)(HO)] } 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 mol-ecules are bonded to the Rb cations; the Na cation is coordinated only to citrate O atoms. Both structures contain an intra-molecular O-H⋯O hydrogen bond between the hy-droxy group and one of the terminal carboxyl-ate groups. In the structure of the dihydrate, each hydrogen atom of the water mol-ecules participates in a hydrogen bond to an ionized carboxyl-ate group.