Novel supramolecular columnar liquid crystals based on thiosemicarbazides

Abstract

Novel liquid crystal materials based on 3,4-di-n-alkoxybenzoylthiosemicarbazides (3a–h, n = 5–10, 12, 14) were synthesised. The mesomorphic properties of these compounds were characterised and studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. Compound 3a did not show mesomorphic properties; 3b shows a monotropic hexagonal columnar (Col_h) phase. Compounds 3c–h display an enantiotropic Col_h phase. The mesomorphic properties were found to be dependent on the length of alkoxy side chains. In N,N-dimethylformamide solution, all the compounds displayed a room temperature emission with λ_max at 361–332 nm. A thermogravimetric analysis also was performed.

Keywords:

• thiosemicarbazides
• columnar liquid crystals
• mesomorphism

Acknowledgements

This work was supported by FONDECYT (1100140), CONICYT, FULLBRIGHT, ‘Dirección de Investigación’ of the University of Concepción. We thank Dr David King for his help in measuring the mass spectra in the laboratory in the Department of Molecular and Cell Biology and Department of Chemical and Biomolecular Engineering, ‘Howard Hughes Medical Institute’, University of California and Miguel Modestino for his collaboration in the measurements of physical parameters in the Department of Chemical and Biomolecular Engineering of the University of California, Berkeley. J.B. thanks the Spanish project CTQ2009-09030.