Columnar to nematic mesophase transition in mixtures of rhodium or copper soaps with hydrocarbon solvents

This paper describes observations of the mesomorphic behaviour of mixtures of rhodium eicosanoate or copper dodecanoate with solvents such as toluene, decahydronaphthalene, and (+) camphene. The mesophase found with these compounds at high temperatures turns from columnar to nematic when the weight fraction of the solvent (toluene, decahydronaphthalene is increased beyond a value of about 50 %. The binary phase diagram of the copper compound with toluene was experimentally determined using polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. The novel feature of the nematic phase is that the basic physical object which align parallel to the nematic director are not individual molecules, but columns of molecules (one-dimensional supramolecular assemblies) which have lost the long-range lateral positional order characteristic of the columnar mesophase. These observations are discussed on the grounds of recent theoretical calculations. Cholesteric-like textures are observed for mixtures of rhodium eicosanoate with the chiral solvent (+) camphene

The structures of the crystalline phase and columnar mesophase of rhodium (II) heptanoate and of its binary mixture with copper (II) heptanoate probed by EXAFS

EXAFS was used to investigate the local structure of the polar spines of rhodium (II) soaps in the columnar liquid crystalline state. It was also used to ascertain the degree of blending of the cores in binary mixtures of rhodium (II) and copper (II) soaps. For the pure rhodium soaps, the columns are shown to result from the stacking of binuclear metal-metal bonded dirhodium tetracarboxylate units bonded to one another by apical ligation of the metal atom of each complex with one of the oxygen atoms of the adjacent molecule. Mixtures of rhodium (II) and copper (II) soaps give a hexagonal columnar mesophase in which pure rhodium and pure copper columns are randomly distributed

Copper K edge EXAFS spectroscopy of the crystalline and columnar phases of copper (II) carboxylates

EXAFS spectra were obtained at the copper-K edge for a series of binuclear copper (II) complexes of fatty acids with 6,12,18 and 22 carbon atoms, in both their crystalline phase and their columnar mesophase. Curve-fitting analysis, using backscattering phases and amplitudes obtained from the structurally characterized copper (II) acetate and copper (II) propionate, gave comparative information on the coordination spheres of copper in both phases. It appeals that the binuclear structure of the complexes and the five-coordination of copper are maintained in the columnar mesophase, with insignificant changes in bond lengths of the binuclear core