Structural characterization and physical properties of new tetrabenzopentaphene mesogens

The synthesis, structural and mesomorphic properties of five tetrabenzopentaphene derivatives are presented. All the compounds exhibit columnar mesophases which have been characterized by optical microscopy, differential scanning calorimetry and X-ray diffraction. The thermogravimetric analysis of the ester derivatives reveals that they suffer a decomposition process to the anhydride derivative at temperatures above 200 degrees C. The influence of the length of the terminal alkyl chains on the mesomorphic behaviour of the compounds has been studied. The structural characterization of the compounds has been completed with the study of their aggregation in solution by means of NMR. The fluorescent properties of the compounds are reported as well as a preliminary study of the photoconductivity of one of them.