Tricaesium tris(oxalato-κ2O1,O2)chromate(III) dihydrate

The title compound, Cs-3[Cr(C2O4)(3)]center dot 2H(2)O, has been synthesized for the first time and the spatial arrangement of the cations and anions is compared with those of the other members of the alkali metal series. The structure is built up of alternating layers of either the d or l enantiomers of [Cr(oxalate)(3)](3-). Of note is that the distribution of the [Cr(oxalate)(3)](3-) enantiomers in the Li+, K+ and Rb+ tris(oxalato)chromates differs from those of the Na+ and Cs+ tris(oxalato) chromates, and also differs within the corresponding BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene] conducting salts. The use of tris(oxalato) chromate anions in the crystal engineering of BEDT-TTF salts is discussed, wherein the salts can be paramagnetic superconductors, semiconductors or metallic proton conductors, depending on whether the counter-cation is NH4+, H3O+, Li+, Na+, K+, Rb+ or Cs+. These materials can also be superconducting or semiconducting, depending on the spatial distribution of the d and l enantiomers of [Cr(oxalate)(3)](3-).