Room-temperature discotic liquid-crystalline coronene diimides exhibiting high charge-carrier mobility in air

Six N,N',5,11-tetrasubstituted coronene-2,3,8,9-tetracarboxydiimides have been synthesised incorporating 3,4,5-tri(n-dodecyloxy) phenyl or 2-(n-decyl)-n-tetradecyl groups in various positions. Differential scanning calorimetry, polarised optical microscopy, and X-ray diffraction indicate that all form columnar discotic mesophases from around room temperature to around 200 degrees C. Charge-carrier mobility values, which energetic considerations suggest are electron mobility values, have been determined in non-aligned samples cooled from the isotropic melt using the space-charge-limited current technique. The highest mobility, 6.7 cm(2) V-1 s(-1), was found in N,N'-bis(n-2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecylfluorooctyl)-5,11-bis(3-[{3,4,5-tri(n-dodecyloxy)phenyl} carbonyloxy]-n-propyl) coronene-2,3,8,9-tetracarboxydiimide, which X-ray diffraction suggests is the most highly ordered of the materials examined.