On the reported mesomorphism of lanthanide complexes containing the hemicyanine structural unit

Close examination of the thermal behaviour of the (E)-N-hexadecyl-4-N', N'-dimethylaminostilbazolium tetrakis(1-phenyl-3-methyl-4-benzoyl-5-pyrazolonato)lanthanide(III) complexes has revealed that these compounds are not mesomorphic, in contradiction to an earlier report in the literature (K. Z. Wang et al., 1995, Solid State Commun. 95, 223). By replacing the bromide of the hemicyanine precursor (see the scheme) by a tetrakis(beta-diketonato)lanthanide(III) anion, new complexes were synthesized, but none shows a mesophase. Reasons for the absence of mesomorphism are discussed. Transition temperatures for the mesomorphic hemicyanine bromides are reported.