Liquid Crystals ofN,N‘-Dialkylimidazolium Salts Comprising Palladium(II) and Copper(II) Ions

Metal-containing ionic liquid crystals of N,N‘-dialkylimidazolium salts of PdII and CuII ([(CnH2n+1)2-im][MCl4], n = 8, 10, 12, 14, 16, and 18 for M = PdII and n = 10, 12, 14, 16, and 18 for M = CuII) were prepared. Crystal structures of two compounds, [(C12H25)2-im]2[PdCl4] and [(C12H25)2-im]2[CuCl4]·H2O, have been characterized by single crystal X-ray diffraction. The cations of these two compounds adopt a U-shaped conformation and are packed in a highly interdigitated bilayer fashion. The square planar PdCl42- and distorted tetrahedral CuCl42- are sandwiched between the cationic bilayers individually. Both series of compounds exhibit a wide temperature range of SmA mesophase. Thermal decompositions are observed near the clearing tempertures. For the PdII series, decomposition generates palladium dicarbene and carbene-imidazole complexes. Ionic liquid crystals with different combinations of [(C18H37)2-im]2[PdCl4], [(C18H37)2-im]2[CuCl4]·H2O, and [(C18H37)2-im]Cl·H2O are good candidates for PdII/CuII catalyzed reactions carried out under partially ordered environments of ionic liquids.