Synthesis and Properties of Organic Hexahalocerate(III) Salts.

A series of hexahalocerate(III) salts with the general formula [cation]₃[CeHal₆] have been prepared by dissolving anhydrous cerium trihalides in imidazolium halide ionic liquids. Complexes with different anions, [CeCl₆]^3-, [CeBr₆]^3- and [CeBr₃Cl₃]^3-, were synthesized and their cationic alkyl chains were varied. To confirm the structures of the prepared salts, X-ray crystallography was used to characterize [BMIM]₃[CeCl₆]. Two different crystal structures were found: [BMIM]₃[CeCl₆] and the linear coordination polymer [BMIM] _x[Ce(µ-Cl)₂Cl₂(EtOH)₂] _x containing coordinated solvent. All the synthesized compounds were characterized by DSC and TGA. The influence of the cationic and anionic structures on the melting points and decomposition temperatures is discussed. Furthermore, the Ce-containing salts [BMIM]₃[CeHal₆] show interesting photoluminescence properties: intense Ce³⁺-based 5d-4f-centred emission from the soft UV-B region to the border of visible light is observed that is driven both by direct excitation of Ce³⁺ as well as by a sensitizer effect of the [BMIM]⁺ cation. [ABSTRACT FROM AUTHOR]