Metal complexes, mesogenic properties

Finally, 4-pentyl-4 -cyanobiphenyl (CB), a compound with mesogenic properties, has been co-condensed with europium and samarium atoms. On the basis of matrix IR spectra and DFT calculations at the B3LYP level, it has been proposed that at low temperatures (below 30 K) mononuclear sandwich complexes [(CB)2Eu] and [(CB)2Sm] were obtained while with higher concentration of metal and at higher temperatures bimetallic sandwich complexes [(CB)2Eu2] and [(CB)2Sm2] were present, in which both phenyl rings of CB are coordinated to Eu or Sm (Vlasov et al., 2005). 

Thermotropic liquid crystalline polymers containing P-diketonato groups 11 give inter-chain complexation of the diketonato groups with Cu(II) and Ni(II) [27]. ESR indicates that square-planar coordination is present in the case of Cu(II), orientated parallel to the fiber axis. Too high a metal content suppresses the mesogenic properties owing to the insolubility and reduced mobility of the... 

Lateral monofluorination of the p-alkoxyphenyl isocyanide system [XAu (CNC6H40C H2 +i)] (X = C1, Br, I), in ortho-(3-F) (6a) and meta-(2-F) (6b) positions relative to the alkoxy chain was also studied [18]. None of the free fluorinated ligands is a LC, but their gold complexes display mesomorphic properties. This is a typical case of a promesogenic ligand which yields a mesogen upon coordination to a metal. 

Ordered (and partially ordered) arrays of metal sites and complexes enable the cooperation of their special electronic, magnetic and optical properties. Such materials have long been sought for their expected physical properties and applications in optics, electrooptics, superconductivity and sensors. The ordering can be by various mechanisms, such as adsorption on surfaces, intercalation into layered structures, formation of mesomorphic structures and liquid crystals, and adoption of specific crystal-packing motifs, all of which are supramolecular phenomena. Organic liquid crystals and their applications are now commonplace, and in recent years the incorporation of metal atoms into mesogenic molecules has demonstrated the occurrence of similar metallo-mesophases [20]. 

---