Synthesis, mesomorphic and photophysical properties of novel triads and pentads of perylene liquid crystals with cholesterol units at the bay-position

Series of triads and pentads of perylene derivatives with two cholesterol units at the bay-position or four cholesterol units on both bay-position and imide position were designed and synthesized in yields of 55–65%. The influence of the different number and position of cholesterol substituents on mesomorphic properties and photophysical properties was studied. The results suggested that, in comparison with similar perylene derivatives with alkyl units at the imide position, the perylene liquid crystals with alkyl units at the bay-positions not only maintained excellent mesomorphic properties but also enhanced the fluorescence greatly. More cholesterol units resulted in a lower mesophase temperature, wider phase transfer temperature range, and higher fluorescence. A long spacer between perylene and cholesterol units led to more excellent mesomorphic properties and higher fluorescence.