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The unique reactivity of molecules under force commands an understanding of structure–mechanochemical activity relationships. While conceptual frameworks for understanding force transduction in many systems are established, systematic investigations into force-coupled molecular torsions are limited. Here, we describe a novel fluorenyl naphthopyran mechanophore for which mechanical force is uniquely coupled to the torsional motions associated with the overall chemical transformation as a result of the conformational rigidity imposed by the fluorene group. Using a combined experimental and theoretical approach, we demonstrate that variation in the pulling geometry on the fluorene subunit results in significant differences in mechanochemical activity due to pronounced changes in how force is coupled to distinct torsional motions and their coherence with the nuclear motions that accompany the force-free ring-opening reaction. Notably, subtle changes in polymer attachment position lead to a >50% difference in the rate of mechanochemical activation in ultrasonication experiments. Our results offer new insights into the structural and geometric factors that influence mechanochemical reactivity by describing how mechanical force is coupled to a reaction that principally involves torsional motions.
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Allosteric control of olefin isomerization kinetics via remote metal binding and its mechanochemical analysis
Abstract Allosteric control of reaction thermodynamics is well understood, but the mechanisms by which changes in local geometries of receptor sites lower activation reaction barriers in electronically uncoupled, remote reaction moieties remain relatively unexplored. Here we report a molecular scaffold in which the rate of thermal E-to-Z isomerization of an alkene increases by a factor of as much as 10 4 in response to fast binding of a metal ion to a remote receptor site. A mechanochemical model of the olefin coupled to a compressive harmonic spring reproduces the observed acceleration quantitatively, adding the studied isomerization to the very few reactions demonstrated to be sensitive to extrinsic compressive force. The work validates experimentally the generalization of mechanochemical kinetics to compressive loads and demonstrates that the formalism of force-coupled reactivity offers a productive framework for the quantitative analysis of the molecular basis of allosteric control of reaction kinetics. Important differences in the effects of compressive vs. tensile force on the kinetic stabilities of molecules are discussed.
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- Award ID(s):
- 1808518
- PAR ID:
- 10466093
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41467-023-40842-5
