Skeletal or concave polyhedral crystals appear in a variety of synthetic processes and natural environments. However, their morphology, size, and orientation are difficult to control because of their highly kinetic growth character. We report a methodology to achieve synchronous, uniaxial, and stepwise growth of micrometer-scale skeletal single crystals from planar-chiral double-decker molecules. Upon drop-casting of a heated ethanol solution onto a quartz substrate, the molecules spontaneously assemble into standing vessel-shaped single crystals uniaxially and synchronously over the wide area of the substrate, with small size polydispersity. The crystal edge is active even after consumption of the molecules and resumes stereoselective growth with successive feeding. The resultant morphology can be packed into polycyclic aromatic hydrocarbon–like microarchitectures and behaves as a microscopic container.
Both enantiomers of a one-handed helical molecule consisting of an o-arylene-ethynylene skeleton were prepared using a planar chiral [2.2]paracyclophane. The helicity of the molecule was controlled by its planar chirality. Excellent chiroptical properties were observed; in particular, the molecule emitted intense circularly polarized luminescence with a high |glum| value of the order of 10−2.
Chiral π-stacked molecules were prepared from planar chiral bis-(para)-pseudo-meta-type [2.2]paracyclophane. π-Electron systems were stacked to form a V-shaped structure with an angle of 120°. Optical and chiroptical properties were experimentally and theoretically investigated and compared with those of the V-shaped molecules comprising the same π-electron systems based on bis-(para)-pseudo-ortho-type [2.2]paracyclophane with an angle of 60°.
The correlation between the orientation of the two π-electron systems and the chiroptical properties was investigated using two types of optically active X-shaped molecules consisting of planar chiral [2.2]paracyclophanes. The X-shaped molecules exhibited high photoluminescence quantum efficiencies and good circularly polarized luminescence properties with relatively high anisotropy factors of the order of 10 À 3 . It was experimentally and theoretically elucidated that the chiroptical properties of the two molecules were almost identical, regardless of the orientation of the stacked π-electron systems.
Two kinds of optically active V‐shaped molecules were synthesized from enantiopure disubstituted and tetrasubstituted [2.2]paracyclophane as chiral building blocks. The p‐arylene‐ethynylene‐type π‐electron systems in these species were stacked at an angle of 60°, and although the two molecules consisted of the same π‐electron system, the orientations of these systems were different. In addition, their optical properties were almost identical, while in contrast, significant differences were observed between their chiroptical properties. It was therefore suggested that circularly polarized luminescence behavior could be controlled by adjusting the orientation of the stacked π‐electron systems.
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