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Title: Mechanochemical Reactivity of a Multimodal 2H-Bis-Naphthopyran Mechanophore
Multimodal mechanophores that react under mechanical force to produce discrete product states with uniquely coupled absorption properties are interesting targets for the design of force-sensing polymers. Herein, we investigate the reactivity of a 2H-bis-naphthopyran mechanophore that generates thermally persistent mono-merocyanine and bis-merocyanine products upon mechanical activation in solution using ultrasonication, distinct from the thermally reversible products generated photochemically. We demonstrate that a force-mediated ester C(O)–O bond scission reaction following ring opening establishes an intramolecular hydrogen bond, locking one merocyanine subunit in the open form. Model compound studies suggest that this locked subunit confers remarkable thermal stability to bis-merocyanine isomers possessing a trans exocyclic alkene on the other subunit, implicating the formation of an unusual trans merocyanine isomer as the product of mechanochemical activation. Density functional theory calculations unexpectedly predict a thermally reversible retro-cyclization reaction of the bis-merocyanine species that could explain the mechanochemical generation of the unusual trans merocyanine isomer.  more » « less
Award ID(s):
2145791
PAR ID:
10491097
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Royal Society of Chemistry
Date Published:
Journal Name:
Polymer Chemistry
Volume:
14
Issue:
22
ISSN:
1759-9954
Page Range / eLocation ID:
2717 to 2723
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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