A₂[MX₄] Copper(II) Pyridinium Salts. From Ionic Liquids to Layered Solids to Liquid Crystals

Abstract

The synthesis and characterization of a novel series of tetrachlorocuprate salts, based on N-alkylpyridinium cations ([Cn−Py]+), are described. The [Cn−Py]2[CuCl4] salts (n = 6, 9−18) were found to be crystalline solids except for the short-chain homologues (n = 6, 9, 10), which were obtained as viscous liquids. X-ray powder diffraction measurements showed that in the crystalline state the ionic species give rise to layered structures. An X-ray crystal structure study of [C15−Py]2[CuCl4] also confirmed the lamellar packing and revealed the monolayer type of organization with strong interdigitation and canting of N-alkyl chains. Most solid salts (n ≥ 12) are thermotropic liquid crystals, with hexagonal columnar, cubic, and smectic phases appearing in the order of increasing chain length and/or temperature. This unique phase behavior has been undoubtedly proved by optical, calorimetric, and diffractometric techniques. The details of the structural organization in both the columnar and cubic phases are not entirely defined yet.

Photoreduction of a crystalline Au(III) complex: A solidstate approach to metallic nanostructures

“…36 degrees with respect to the layer normal, similar to 3d metal ILCs. [5][6][7][8] The smaller layer spacing in our complex (15.5 Å vs. 17.2 Å in the Cu analog) is assigned to the fact that the corresponding Cu complex contains two ligand molecules per formula unit, 8 X-ray pattern of 1 with the most prominent reflections. Inset: estimation of the length of the fully stretched ligand molecule DSC traces of 1 exhibit an intense exothermic peak between 55 and 120°C on first heating.…”

“…Gold platelet precursor Structurally, the complex 1 is an Au(III) analog of the many 3d and 4d metal alkylpyridinium complexes reported in the literature [4][5][6][7][8]18 which are crystalline at room temperature and show thermotropic liquid crystal behavior. Like these compounds, 1 is crystalline at room temperature.…”

“…2,3 Moreover, the pyridinium and imidazolium cations of ILs can coordinate to MX 4 2-(M = Co, Ni, Cu, Zn, Cd, Pd and X = Cl, Br) complex ions and form ionic liquid crystals (ILCs). [4][5][6][7][8][9][10][11] Because these ILCs contain a metal center and have a high degree of order, they are prime candidates for the synthesis of inorganic nanostructures. As the first example, our group has recently fabricated a macroporous network of CuCl platelets from a Cu-containing ILC.…”

Piperidinium, Piperazinium and Morpholinium Ionic Liquid Crystals

“…These cations were combined with several types of anions, namely bromide, tetrafluoroborate, hexafluorophosphate, dodecylsulfate, bis(trifluoromethylsulfonyl)imide, dioctylsulfosuccinate, dicyclohexylsulfosuccinate, and dihexylsulfosuccinate. For the bromide salts of piperidinium containing one alkyl chain, the chain length was varied, ranging from 8 to 18 carbon atoms (n ) 8, 10,12,14,16,18). The compounds show a rich mesomorphic behavior.…”

Supramolecular Structures in the Presence of Ionic Liquids

“…The ionic conductivities and LC structures of the obtained 1-methylimidazolium ILs could be conveniently adjusted by anions, which would potentially be used as an on-off switch of ions ( Figure 17) (Yazaki et al, 2008b). Besides imidazolium ionic LCs, other thermotropic ionic LCs based on pyridinium (Bowlas et al, 1996;Cruz et al, 2000;Cui et al, 2002;Gordon et al, 1998;Neve et al, 2000;Neve et al, 2001;Taubert, 2004), quaternary ammonium (Alami et al, 1993;Arkas et al, 1999;Lu et al, 1997;Pott & Meleard, 2009;Tittarelli et al, 1997), quaternary phosphonium (Abdallah et al, 2000;Chen et al, 2002;Gowda et al, 2004), pyrrolidinium (Goossens et al, 2009), dithiolium (Artzner et al, 1997) and guanidinium ILs (Kim et al, 2005;Mathevet et al, 2005;Sauer et al, 2008) have also been explored. Two important phenomena should be especially noticed.…”