Polycyclic aromatic hydrocarbons (PAHs) are promising for materials science because of their high thermal and chemical stability, electron mobility, and unique photophysical properties. However, flat PAHs have limited applications owing to the low processability of their solutions, which originates from the strong π–π interaction between the aromatic rings. Herein, we report an effective method to suppress the π–π stacking of flat and large PAHs through steric hindrance. A 2,6-dimethylphenyl group, which is referred to as the “picket-fence” (PF) group based on its fence-like shape, was introduced on the edge of hexa-peri-hexabenzocoronene (HBC) through a bottom-up synthetic process. The PF group enhanced the solubility of HBC, while the unique photophysical properties of the core structure were preserved even in the solid state. The steric effect of the PF group is also demonstrated with other flat PAHs, which show excellent solid-state photophysical properties after functionalization with the PF group. Experimental and theoretical results indicate that the picket size plays a critical role in adjusting the PF effect. Furthermore, we fabricated the first organic light-emitting diode (OLED) that uses an HBC-based emitter, and the solid-state emission spectrum of the device is almost the same as that of the emitter in solution. This is possibly due to the maintenance of their morphology without aggregation due to the PF effect. Moreover, the full width at half maximum of the electroluminescence band was very narrow at only 20 nm.

Bone diseases may not be imminently life-threatening or a leading cause of death such as heart diseases or cancers. However, as aging population grows in almost every part of the world, they surely impose significant socioeconomic burden on the society, not to mention the patients and their families. Osteoporosis is the most common type of bone disease, which frequently develops in seniors, especially in postmenopausal women. Although currently several anti-osteoclastic drugs designed to suppress excessive osteoclast activation, a major cause of osteoporosis, are commercially available, accompanying adverse effects ranging from mild to severe have been reported as well. Natural products have become increasingly popular because of their effectiveness with fewer side effects. Isoliquiritigenin (ILG), a natural flavonoid from licorice, has been reported to suppress osteoclast differentiation and activation. In the present study, newly synthesized ILG derivatives were screened for their anti-osteoporotic activity as more potent substitute candidates to ILG. Out of the 12 ILG derivatives tested, two compounds demonstrated significantly improved bone loss in vitro by inhibiting both osteoclastogenesis and osteoclast activity. The results of the present study indicate that these compounds may serve as a potential drug for osteoporosis and warrant further studies to evaluate their in vivo efficacy.