Novel Class of Ambipolar Columnar Liquid Crystals Based on Cyclic Dipeptide and Isatin Hybrids

A new class of cyclic dipeptide-isatin hybrids was synthesized using 2,5-diketopiperazine and various isatin derivatives bearing flexible chains and extended aromatic rings in a double Knoevenagel condensation process. These new series demonstrate high solubility and good thermal stability with decomposition temperatures exceeding 370 °C, especially the molecular design with efficient space-filling (CI5 and CI6) stabilized columnar liquid crystalline phase. The hole and electron carrier mobility of the CI5 compound, measured using the space charge limited current (SCLC) technique, were found to be 9.46×10 cm/V.s and 7.88×10 cm/V.s respectively. The stabilization of columnar self-assembly and observation of ambipolar charge carrier mobility in cyclic dipeptide-isatin hybrids make them a promising class of self-assembling organic semiconductors.