Möbius ZnII‐Hexaphyrins Bearing a Chiral Coordinating Arm: A Chiroptical Switch Featuring P/M Twist Inversion Controlled by Achiral Effectors

By their conformational flexibility, Möbius aromatic hexaphyrins provide a dynamic chirality attractive to develop stimuli responsive systems such as chiroptical switches. A regular [28]hexaphyrin has been equipped with a chiral coordinating arm to achieve transfer of chirality from a fix stereogeni...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2022-02, Vol.61 (6), p.e202113844-n/a
Main Authors: Ruffin, Hervé, Fihey, Arnaud, Boitrel, Bernard, Le Gac, Stéphane
Format: Article
Language:English
Subjects:
Chirality
chiroptical properties
Circular dichroism
Coordination compounds
Dichroism
dynamic chirality
Effectors
Ligands
molecular recognition
Möbius aromaticity
porphyrinoids
Stereoselectivity
Switches
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Summary:By their conformational flexibility, Möbius aromatic hexaphyrins provide a dynamic chirality attractive to develop stimuli responsive systems such as chiroptical switches. A regular [28]hexaphyrin has been equipped with a chiral coordinating arm to achieve transfer of chirality from a fix stereogenic element to the dynamic Möbius one. The arm allows straightforward formation of labile monometallic ZnII complexes with an exogenous ligand, either a carboxylato or an amino with opposite inwards/outwards orientations relative to the Möbius ring. As a corollary, the chiral coordinating arm is constrained over the ring or laterally, inducing opposite P and M Möbius configurations with unprecedented high stereoselectivity (diast. excess greater than 95 %). By tuning the transfer of chirality, these achiral effectors generate electronic circular dichroism spectra with bisignate Cotton effect of opposite signs. Switching between distinct chiroptical states was ultimately achieved in mild conditions owing to ligand exchange, with high robustness (10 cycles). How far can the dynamic chirality of Möbius hexaphyrins be controlled lies firstly on the capacity of an attached source of chirality to explore the Möbius ring environment, which depends on several convoluted dynamic processes; secondly on the responsiveness of the system, making this exploration tunable and multi‐reversible; and thirdly on the unwavering optimism of the experimenter.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.202113844