Rare-earth-containing metallomesogens with 4-alkoxy-N-alkyl-2-hydroxybenzaldimine ligands are reported. The stoichiometry of the complexes is [Ln(LH) 3 (NO 3 ) 3 ], where Ln is the trivalent rare-earth ion (Y, La, and Pr to Lu, except Pm) and LH is the Schiff base. The Schiff base ligands are in the zwitterionic form and coordinate through the phenolic oxygen only. The three nitrate groups coordinate in a bidentate fashion. The X-ray single-crystal structures of the nonmesogenic homologous complexes [Ln(LH) 3 (NO 3 ) 3 ], where Ln ) Nd(III), Tb(III), and Dy(III) and LH ) CH 3 OC 6 H 3 (2-OH)CHdNC 4 H 9 , are described. Although the Schiff base ligands do not exhibit a mesophase, the metal complexes do (SmA phase). The mesogenic rare-earth complexes were studied by NMR, IR, EPR, magnetic susceptibility measurements, X-ray diffraction, and molecular modeling. The metal complexes in the mesophase have a very large magnetic anisotropy, so that these magnetic liquid crystals can easily be aligned by an external magnetic field.

Lanthanide complexes of the Schiff base ligand 4-dodecyloxy-N-hexadecyl-2-hydroxybenzaldimine and with perfluorinated alkyl sulfate counterions were synthesised. All of the metal complexes show a smectic A mesophase. The viscosity of this mesophase is much lower than that of analogous compounds with nitrate or alkyl sulfate counterions. The behaviour of these new highly anisotropic molecular magnetic materials was studied using high-temperature X-ray measurements in an external magnetic field and temperature-dependent magnetic susceptibility measurements. The mu(eff)-versus-temperature curve is more comparable with those expected for nematic phases than for smectic phases. The luminescence spectrum of a EuIII compound shows that the values of the second rank crystal field parameters are very large. The huge magnetic anisotropy can be related to this strong crystal-field perturbation.

Lanthanide complexes of the Schiff base ligand 4-dodecyloxy-N-hexa-decyl-2-hydroxybenzaldimine and with perfluorinated alkyl sulfate counterions were synthesised. All of the metal complexes show a smectic A mesophase. The viscosity of this mesophase is much lower than that of analogous compounds with nitrate or alkyl sulfate counterions. The behaviour of these new highly anisotropic molecular magnetic materials was studied using high-temperature X-ray measurements in an external magnetic field and temperature-dependent magnetic susceptibility measurements. The m eff-versus-temperature curve is more comparable with those expected for nematic phases than for smectic phases. The luminescence spectrum of a Eu III compound shows that the values of the second rank crystal field parameters are very large. The huge magnetic anisotropy can be related to this strong crystal-field perturbation.

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1995): Correlation between magnetic properties and molecular structure of some metallo-mesogens, Liquid Crystals, 18:2, 231-237To link to this article: http://dx.

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