| Abstract
| - The connection of lipophilic gallic acid derivatives at the 5,5‘- or 6,6‘-positions of the rigid 2,6-bis(1-ethyl-benzimidazol-2-yl)pyridine core provides two pro-mesogenic tridentate ligands L10 and L12,whose molecular shapes, anisometries, and directional intermolecular π-stacking can be tuned. X-raydiffraction data in the crystalline state, combined with solution 1H NMR measurements, show thatcomplexation 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 [Ln2(Li)2(NO3)6] at lower temperature.The relevant thermodynamic parameters for the latter process depend on the nature of the ligand, the sizeof the metal ion, and the strength of the intermolecular interactions involved in the condensed phase. Thesethree-dimensional models obtained for the complexes in the crystals and in solution are eventually confrontedwith small-angle XRD profiles recorded in the intermediate thermotropic liquid crystalline phase, in whichthe rigidity of the packed polyaromatic cores is maintained, while the alkyl chains are molten. According tothe 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 microscopicarrangements and the macroscopic ordering in lanthanide-containing metallomesogens.
|
