Dynamic Motion of Twisted π System-Induced Temperature-Dependent Dielectric Response in the Neat Liquid State

Abstract

Molecular assemblies of twisted π molecules of tetraphenylene with long alkoxy chains (1) and tetra[2,3]thienylene with long alkylamide chains (2) or long alkoxy chains (3) and their dielectric properties were investigated. Different degrees of intermolecular interaction of 1–3 afforded different molecular assemblies, including an ordered columnar structure, disordered columnar, and lamellar structures. The introduction of long alkyl chains enabled us to create thermally stable liquid crystalline or liquid states. Temperature-dependent dielectric measurement revealed that the dynamic flipping motion of the tetra[2,3]thienylene core of 3 induced a temperature- and frequency-dependent dielectric anomaly in the neat liquid phase. This flipping motion of the central tetra[2,3]thienylene π core occurred relatively easily in the liquid state with a high degree of freedom of molecular motion.