Extended Conjugation Attenuates the Quenching of Aggregation‐Induced Emitters by Photocyclization Pathways

Herein, we expose how the antagonistic relationship between solid‐state luminescence and photocyclization of oligoaryl alkene chromophores is modulated by the conjugation length of their alkenyl backbones. Heptaaryl cycloheptatriene molecular rotors exhibit aggregation‐induced emission characteristi...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2022-06, Vol.61 (24), p.e202202193-n/a
Main Authors: Turley, Andrew T., Saha, Promeet K., Danos, Andrew, Bismillah, Aisha N., Monkman, Andrew P., Yufit, Dmitry S., Curchod, Basile F. E., Etherington, Marc K., McGonigal, Paul R.
Format: Article
Language:English
Subjects:
Agglomeration
Aggregation-Induced Emission
Alkenes
Carbocycles
Chromophores
Conjugation
Emissions
Emissions control
Emitters
Fluorescence
Molecular Rotors
Photochemistry
Photoluminescence
Photons
Polycyclic aromatic hydrocarbons
Quenching
Rotors
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Summary:Herein, we expose how the antagonistic relationship between solid‐state luminescence and photocyclization of oligoaryl alkene chromophores is modulated by the conjugation length of their alkenyl backbones. Heptaaryl cycloheptatriene molecular rotors exhibit aggregation‐induced emission characteristics. We show that their emission is turned off upon breaking the conjugation of the cycloheptatriene by epoxide formation. While this modification is deleterious to photoluminescence, it enables formation of extended polycyclic frameworks by Mallory reactions. We exploit this dichotomy (i) to manipulate emission properties in a controlled manner and (ii) as a synthetic tool to link together pairs of phenyl rings in a specific sequence. This method to alter the tendency of oligoaryl alkenes to undergo photocyclization can inform the design of solid‐state emitters that avoid this quenching mechanism, while also allowing selective cyclization in syntheses of polycyclic aromatic hydrocarbons. Reactions to shorten and lengthen the conjugation between oligoaryl alkene units of aggregation‐induced emitters toggle between rapid photocyclization and efficient photoluminescence properties. Trienes are resistant to photocyclization, giving them higher photoluminescence quantum yields, whereas nonconjugated aryl alkene units cyclize readily to form extended polycyclic frameworks.
ISSN:1433-7851
1521-3773
1521-3773
DOI:10.1002/anie.202202193