Manipulations of Chiroptical Properties in Belt‐Persistent Cycloarylenes via Desymmetrization with Heteroatom Doping

A desymmetrization strategy has been devised in the design of molecular cylinders to maximize the dissymmetry factor relevant to circularly polarized light. Although the highest dissymmetry factor of organic molecules was previously achieved with a chiral belt‐persistent cycloarylene having magnetic...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2021-08, Vol.60 (35), p.19097-19101
Main Authors: Fukunaga, Toshiya M., Sawabe, Chizuru, Matsuno, Taisuke, Takeya, Jun, Okamoto, Toshihiro, Isobe, Hiroyuki
Format: Article
Language:English
Subjects:
Belts
chirality
circular dichroism
Circular polarization
Coupling (molecular)
Cross coupling
cylinders
Dipole moments
macrocycles
nanotubes
Organic chemistry
Polarized light
Stereoselectivity
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Summary:A desymmetrization strategy has been devised in the design of molecular cylinders to maximize the dissymmetry factor relevant to circularly polarized light. Although the highest dissymmetry factor of organic molecules was previously achieved with a chiral belt‐persistent cycloarylene having magnetic and electric transition dipole moments in parallel, we noticed that an unbalanced magnitude of two moments was detrimental for higher dissymmetry factors. In this study, a molecular cylinder was desymmetrized by arraying doped and undoped panels via stereoselective cross‐coupling macrocyclization. The desymmetrization succeeded in balancing two moments by reducing the electric transition moment at the global minimum but failed to maximize the dissymmetry factor. Structural studies revealed that the dissymmetry factor is sensitive to subtle structural fluctuations, while the rotatory strength is not affected. This study is important for the development of chiroptical materials. Desymmetrization of chiral cylindrical cycloarylenes ought to be beneficial to maximize the dissymmetry factor g via reduction of the electric dipole moment μ. An ideal D2 molecule has been synthesized by cross‐coupling macrocyclization of two different arylene panels. Twists in biaryl linkages, however, enlarged an orthogonal component of μ, and the inclined and enlarged μ moment resulted in a much smaller g than expected.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.202106992