Dielectric Response of Difluorinated Sumanene Caused by the In-plane Motion

In this work, we designed and synthesized a new curved π-conjugated molecule difluorosumanene (1), which possesses two fluorine atoms on the same benzylic carbon on pristine sumanene to possess a large dipole moment along the in-plane direction. Thermal analyses, variable temperature X-ray diffraction and IR measurements indicated the 120° in-plane motion of 1 in the stacking columns, which did not cause any phase transition in the crystalline state. Indeed, the dielectric measurement using its both powder and single crystal showed that both real (ε1) and imaginary (ε2) parts of the dielectric constant were enhanced above ~360 K at 1 MHz with a Debye-type dielectric relaxation, confirming the pendulum fluctuation of 1 induced by the external electric field.