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

Metal-containing ionic liquid crystals of N, N ‘-dialkylimidazolium salts of Pd II and Cu II ([(C n H 2 n +1 ) 2 -im][MCl 4 ], n = 8, 10, 12, 14, 16, and 18 for M = Pd II and n = 10, 12, 14, 16, and 18 for M = Cu II ) were prepared. Crystal structures of two compounds, [(C 12 H 25 ) 2 -im] 2 [PdCl 4 ] and [(C 12 H 25 ) 2 -im] 2 [CuCl 4 ]·H 2 O, 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 PdCl 4 2 - and distorted tetrahedral CuCl 4 2 - 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 Pd II series, decomposition generates palladium dicarbene and carbene-imidazole complexes. Ionic liquid crystals with different combinations of [(C 18 H 37 ) 2 -im] 2 [PdCl 4 ], [(C 18 H 37 ) 2 -im] 2 [CuCl 4 ]·H 2 O, and [(C 18 H 37 ) 2 -im]Cl·H 2 O are good candidates for Pd II /Cu II catalyzed reactions carried out under partially ordered environments of ionic liquids.