Rare-earth complexes of mesomorphic Schiff's base ligands

Rare-earth complexes of mesomorphicSchiff's bases, 4-[(alkylimino)methyl]-3 -hydroxyphenyl-4- alkyloxybenzoates, were synthesized. Whereas the ligands LH display a nematic and/or a smectic C phase, the metal complexes show a v iscous smectic A phase and decompose at the clearing point. The mesophase w as investigated by hot-stage polarizing optical microscopy, by differential scanning calorimetry and by high temperature X-ray diffraction. Two types of complex were found, [Ln(LH)(3)(NO3)(3)] and [Ln(LH)(2)L(NO3)(2)], depend ing on the ligand or the central metal ion. The first coordination sphere o f the rare-earth ion in these metallomesogens is comparable to that in the structure of complexes with 4- alkoxy-N-alkyl-2-hydroxybenzaldimine ligands .