|Title: ||Phenanthrolines as versatile ligands for the design of liquid-crystalline metal complexes|
|Authors: ||Binnemans, Koen|
Donnio, Bertrand #
|Issue Date: ||2005 |
|Conference: ||XLVIII. Meeting of the Polish Chemical Society location:Poznan (Poland) date:18-22 September 2005|
|Abstract: ||Although 1,10-phenanthrolines have been very often used as ligands for metal complexes and although these complexes have interesting photophysical properties, only very few examples of metal-containing liquid crystals with 1,10-phenanthroline ligands have been described in the literature. Moreover, only 3,8- and 2,9-disubstituted 1,10-phenanthrolines have been used as precursors for liquid crystals. We explored different routes to liquid-crystalline 1,10-phenanthrolines disubstituted in either the 5-position and/or the 6-position. Imidazo[4,5-f]1,10-phenanthrolines are very versatile phenanthrolines derivatives that can be prepared by condensation of 1,10-phenanthroline-5,6-dione and a substituted benzaldehyde in the presence of ammonium acetate, and with acetic acid as the solvent. The approach can lead to a whole class of liquid crystals, by a proper choice of the aldehyde.
Liquid-crystalline complexes of rhenium(I), yttrium(III), lanthanum(III), neodymium(III), samarium(III), europium(III), erbium(III) and ytterbium(III) were obtained by coupling mesogenic 4-cyanobiphenyl groups with a long alkyl spacer to a substituted imidazo[4,5-f]1,10-phenanthroline, which acts as the coordinating group. In the case of the rare-earth complexes, 2-thenoyltrifluoroacetonate was used as the co-ligand. The rhenium(I) complexes contain the bromotricarbonylrhenium(I) moiety. All the rare-earth complexes exhibit a nematic phase, whereas the rhenium(I) complexes show a nematic, a smectic C, or a lamello-columnar phase, and the imidazole-bearing phenanthroline ligands a nematic or a smectic phase, depending on the number of attached mesogenic groups. Several of the rare-earth complexes show intense photoluminescence, either in the visible or in the near-infrared region. The rhenium(I) complexes are luminescent as well.
Besides trivalent rare-earth ions and rhenium(I), complexes of the following metal ions were prepared: iron(II), ruthenium(II), nickel(II), palladium(II), platinum(II) and uranyl. The first examples of ten-coordinate liquid-crystalline metal complexes will be presented.
|Description: ||invited lecture|
|Publication status: ||published|
|KU Leuven publication type: ||AMa|
|Appears in Collections:||Molecular Design and Synthesis|