Lanthanide-Containing Metallomesogens with Low Transition Temperatures

Lanthanide-containing liquid crystals exhibiting a mesophase close to room temperature were obtained by adduct formation between a long-chain salicylaldimine Schiff base and tris(2-thenoyltrifluoroacetonato)lanthanide(III) complexes or tris(benzoyltrifluoroacetonato)lanthanide(III) complexes. The mesophase was identified as a smectic A phase. The temperature range of the mesophase was found to decrease over the lanthanide series, and no mesophase was observed for the complexes of the smallest lanthanide ions. The photoluminescence of the europium(III), samarium(III), neodymium(III), and erbium(III) complexes was studied. It is shown that the clearing point can be detected by monitoring the luminescence decay time as a function of the temperature.