Synthesis, Structure, and Thermotropic Mesomorphism of Layered N-Alkylpyridinium Tetrahalopalladate(II) Salts

Abstract

Two homologous series of N-alkylpyridinium salts, [Cn-Py] 2 [PdX 4 ] (n ) 12, 14, 16, 18; X ) Cl, Br), have been synthesized, and their thermal behavior has been studied by differential scanning calorimetry and hot-stage polarizing optical microscopy. Except for the substances with n ) 12, all the materials show thermotropic polymorphism. The crystal structures of, and [C16-Py] 2 [PdBr 4 ] have been solved. All three complex salts crystallize in the triclinic space group P1 h. Crystal packing reveals layered structures with alternating polar and apolar sublayers, where each [PdX 4 ] 2anion is sandwiched between two antiparallel pyridinium cations. Alkyl chains are highly interdigitated and tilted with respect to the layer normal. The structural characterization of the [Cn-Py] 2 -[PdX 4 ] (n ) 16, 18; X ) Cl, Br) salts has been achieved also through variable-temperature powder X-ray diffraction. The [PdCl 4 ] 2salts undergo transitions to a second crystalline phase and then to an ordered and a disordered smectic phase. The latter are assigned to single-layered smectic-E and partially bilayered smectic-A d phases, respectively. On warming, the [PdBr 4 ] 2analogues only show the smectic-A d phase, preceded by a crystalline phase very similar to the room-temperature solid phase. The relative importance of hydrogen bonding throughout the sequence of structural changes is briefly addressed.

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.…”

Tetrahalidocuprates(ii)—structure and EPR spectroscopy. Part 1: Tetrabromidocuprates(ii)

“…[34][35][36] Reports on tetrahalidometalate-based ILCs and their transformation into inorganic materials are, however, relatively rare. [30][31][32][33][37][38][39][40][41][42][43][44][45][46][47] This is somewhat surprising because metal containing ILs and ILCs may open the door towards a new valuable branch of IL research, which derives its importance from the additional properties such as colour, geometry, or magnetism, which are brought about the material by the metal ion.…”

Palladate Salts from Chiral Pyridinium Ionic Liquids: Synthesis and Crystal Structures

“…Therefore, the solubilities both of organic compounds and of metal salts in ILs are important with regard to chemical synthesis and catalytic processes [4]. The ammonium, phosphonium, 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 to form ionic liquid crystals (ILCs) [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These ILCs contain a metal center, and so have been used as catalyst or catalyst precursors [5].…”