Room-temperature blue-light-emitting liquid crystalline materials based on phenanthroimidazole-substituted carbazole derivatives

Abstract

A new class of highly efficient blue emitters consisting of phenanthroimidazole–carbazole hybrid disc-shaped molecules with two Schiff base units have been designed and well characterized. All the prepared materials exhibited a columnar hexagonal phase (Colh) over a broad temperature range and a stabilized mesophase at room temperature with good thermal stability. Their electrochemical, thermal and photophysical behavior was extensively evaluated using cyclic voltammetry (CV), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized optical microscopy (POM) and UV-visible spectrophotometry. The synthesized compounds exhibited blue-light emission in the solid thin film as well as in the solution state. The number of alkoxy side chains (–OR) substituted at terminal positions inbuilt with Schiff base groups on the phenanthroimidazole-substituted carbazole core showed an influence on the thermal behavior and stability of the mesophase. These types of materials are promising due to their wide range of columnar hexagonal phases, self-assembly and blue-light emission in solution as well as solid state.