Dibenzodiazapyracylenes: Doubly N-Doped Cyclopenta-Fused Polycyclic Molecules That Exhibit High Carrier Mobility.

Pyracylene is a unique cyclopenta-fused polycyclic aromatic hydrocarbon (CP-PAH) that exhibits dual aromatic characteristics. Herein we report the synthesis of doubly N-doped benzannulated pyracylenes, namely dibenzodiazapyracylenes, by oxidative N-N linking reaction of [2.2](2,5)pyrrolophane-type precursors. Dibenzodiazapyracylenes displayed well-ordered π-stacked molecular packing in the solid state, which were feasible for effective hole-transporting along the stacking direction. High carrier mobility was estimated by microwave conductivity measurements as compared to dibenzoullazine. The high HOMO level of dibenzodiazapyracylene was verified by electrochemistry and its persistent radical cation species has been detected.

Probing a microviscosity change at the nematic-isotropic liquid crystal phase transition by a ratiometric flapping fluorophore.

Understanding the microviscosity of soft condensed matter is important to clarify the mechanisms of chemical, physical or biological events occurring at the nanoscale. Here, we report that flapping fluorophores (FLAP) can serve as microviscosity probes capable of detecting small changes. By the ratiometric fluorescence analysis, one of the FLAP probes detects a macroscopic viscosity change of a few cP, occurring at the thermal phase transition of a nematic liquid crystal. We discuss the impact of the chemical structure on the detection capability, and the orientation of the FLAP molecules in the ground and excited states. This work contributes to experimentally providing a molecular picture of liquid crystals, which are often viewed as a continuum.