Jean-Claude Bunzli - Lanthanide luminescent mesomorphic complexes with macrocycles derived from diaza-18-crown-6

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      Suarez,S., Mamula,O., Scopelliti,R., Donnio,B., Guillon,D.,   Terazzi,E., Piguet,C., Bunzli,J.C.G. New Journal of   Chemistry 2005 29 (10) 1323-1334

      Abstract: Four tetracatenar (L1-L4) and one   hexacatenar (L5) ligands, derived from the diaza-18-crown-6   framework, are synthesized and characterized. In these ligands,   the amine functions are fitted with benzoyloxybenzyl linker   groups, attached either with a carbonyl function (L1) or a   methylene bridge (L2-L5) and bearing alkoxy chains, R, of various   lengths: R = OCH3 for L2, OC10H21 for L3 and L5, OC12H25 for L1,   and OC16H33 for L4. The non-mesomorphic ligands L1 and L3-L5   react with various lanthanide salts to give complexes forming   thermotropic hexagonal columnar phases, as ascertained by   thermal, optical and small-angle X-ray diffraction methods. The   length of the alkoxy chains (L3 and U) does not much influence   the mesogenic behaviour, irrespective of the linker function, the   number of alkoxy chains, the counterion or the lanthanide ion.   The best systems proved to be the nitrato lanthanide complexes   with U, which present a Col(h) phase over 100 degrees C (up to   147 degrees C for La) with melting transition temperatures   between 58 (La) and 86 (Tb) degrees C. In the case of   [Eu(NO3)(3)L3], chosen as a representative example of all the   complexes in this analysis, the inter-column separation of 29.2   angstrom agrees well with the packing of cylindrical columns   resulting from an alternated stacking of the molecules, in which   the two mesogenic arms extend on the same side, i.e. stacking the   molecules in a bent conformation. The liquid crystalline phases   containing Eu and Tb display metal-centred emission, meaning that   these complexes are interesting building blocks for the design of   luminescent liquid crystalline materials

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