Jean-Claude Bunzli - Molecular control of macroscopic cubic, columnar, and lamellar organizations in luminescent lanthanide-containing thermotropic liquid crystals

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  Terazzi,E., Torelli,S., Bernardinelli,G., Rivera,J.P.,   Benech,J.M., Bourgogne,C., Donnio,B., Guillon,D., Imbert,D.,   Bunzli,J.C.G., Pinto,A., Jeannerat,D., Piguet,C. Journal of   the American Chemical Society 2005  127 (3) 888-903

  Abstract: The connection of lipophilic gallic   acid derivatives at the 5,5'- or 6,6'-positions of the rigid   2,6bis(1-ethyl-benzimidazol-2-yl)pyridine core provides two   pro-mesogenic tridentate ligands L10 and L12, whose molecular   shapes, anisometries, and directional intermolecular pi-stacking   can be tuned. X-ray diffraction data in the crystalline state,   combined with solution H-1 NMR measurements, show that   complexation with trivalent lanthanides, Ln(III), produces the   neutral hemi-disklike complexes [Ln(Li)(NO3)(3)] (i = 10, 12),   which dimerize to give the rodlike bimetallic complexes   [Ln(2)(Li)(2)(NO3)(6)] at lower temperature. The relevant   thermodynamic parameters for the latter process depend on the   nature of the ligand, the size of the metal ion, and the strength   of the intermolecular interactions involved in the condensed   phase. These three-dimensional models obtained for the complexes   in the crystals and in solution are eventually confronted with   small-angle XRD profiles recorded in the intermediate   thermotropic liquid crystalline phase, in which the rigidity of   the packed polyaromatic cores is maintained, while the alkyl   chains are molten. According to the specific geometries and   nuclearities of the molecular complexes, three types of   mesophases (lamellar, columnar, and cubic) can be induced, which   provides a direct correlation between the microscopic   arrangements and the macroscopic ordering in   lanthanicle-containing metallomesogens

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