Crystal structures of 2,3,6,7,10,11-oxytriphenylenes. Implications for columnar discotic mesophases

The structures of the oxysubstituted triphenylene premesogens, 2,3,6,7,10,11-hexahydroxy-triphenylene (4), 2,3,6,7,10,11-hexamethoxytriphenylene (5), 2,3,6,7,10,11-hexaethoxytriphenylene (6), and 2,3,6,7,10,11-hexapropoxytriphenylene (7) were determined, and the structural results were investigated in the aim that a detailed structural knowledge of the discotic premesogens could be used to infer detailed structural knowledge with respect to known liquid crystal mesogens where little detailed structural knowledge is available. It was found that the crystal structures of the discotic premesogens were very different from the structures expected for discotic columnar behavior. These differences allowed us to shed some light on the structural forces that gives rise to the mesophasic behavior observed in such systems as being not due to stacking of the planar aromatic core as inferred hitherto but rather governed by the alkyl groups.