Planar chiral cyclophane chemistry: excellent circularly polarized luminescence (CPL) emitters
[2.2]Paracyclophane is a unique aromatic compound consisting of two stacked benzene rings in close proximity. Planar chirality, which arises from the proximally fixed benzene rings, is one of the interesting structural characteristics of the [2.2]paracyclophane skeleton. We reported practical methods for the optical resolution of planar chiral 4,12-disubstituted  and 4,7,12,15-tetrasubstituted [2.2]paracyclophanes .
We have synthesized and disclosed planar chiral [2.2]paracyclophane-based conjugated compounds. We reported the first observation of chiral luminescence “circularly polarized luminescence = CPL” from the planar chiral molecules in the world [1b].
CPL active molecules are the promising candidates for 3D light-emitting-devices, liquid crystals, dyes for forgery-prevention of documents, and so on. The representative examples of CPL emitters based on the planar chiral [2.2]paracyclophane skeletons are as follows…
１．Optically active conjugated molecules based on planar chiral di-substituted [2.2]paracyclophane
Optically active V-shaped, N-shaped, and M-shaped oligomers , triangle-shaped cyclic oligomers [1b,3], and zigzag-shaped polymers [1b,4] have been prepared by using planar chiral disubstituted [2.2]paracyclophanes as building blocks.
All molecules exhibited intense CPL; in particular, we reported the first CPL-emitting conjugated polymers in dilute solution [1b]. We suggest that higher-ordered structure of molecules in the excited state is important for CPL.
２．Optically active conjugated molecules based on planar chiral tetra-substituted [2.2]paracyclophane
We achieved the first optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane in the world  and synthesized propeller-shaped [2,5] and X-shaped molecules . The propeller-shaped cyclic compounds exhibited excellent CPL profiles. Thin films of the dendrimers  with a X-shaped core unit exhibited intense CPL by the light-harvesting effect of the dendrons and protecting effect of the core.
Very recently, we synthesized right- and left-handed double helical compounds consisting of two boomerang-shaped compounds stacked in proximity . The compounds emitted intense CPL as well.
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