Synthesis, Mesomorphism, and Unusual Magnetic Behaviour of Lanthanide Complexes with Perfluorinated Counterions

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 μeff ‐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. Anisotropic molecular magnetic materials were obtained by reaction between lanthanide(III) perfluoroalkyl sulfates and a salicylaldimine Schiff base. The compounds exhibit smectic mesomorphism and the viscosity of the mesophase is much lower than for corresponding metal complexes with nitrate counterions. A huge magnetic anisotropy was observed for the compounds of the heavy lanthanides by temperature‐dependent magnetic susceptibility measurements (see picture).