Synthesis and properties of donor-acceptor linked fluorenone liquid crystals

Abstract

We synthesized bilateral symmetric and asymmetric donor-acceptor-type fluorenone derivatives by the Suzuki-Miyaura cross-coupling reaction to evaluate their liquid-crystalline (LC) and electronic properties. These two compounds exhibited thermotropic smectic LC phases including a ferroelectric chiral smectic C (SmC*) phase. In particular, the bilateral symmetric fluorenone derivative showed large spontaneous polarization of 220 nC/cm^2 estimated by the Sawyer-Tower method. Both donor-acceptor-type fluorenone derivatives exhibited ambipolar carrier transport properties in the SmC* phases. The hole and electron mobilities were on the order of 10^−5 cm^2/(V^1 s^1) in the SmC* phases of the fluorenone derivatives. In addition, the intramolecular charge transfer in these two compounds led to enhance the absorption property to the visible light in the thin film state.