Visible-light-mediated Diels-Alder reactions under single-chain polymer confinement: investigating the role of the crosslinking moiety on catalyst activity

Macromolecular scaffolds are rapidly emerging in catalysis owing to the ability to control catalyst placement at precise locations. This spatial proximity allows for enhanced catalyst activity that may not be observed using small molecules. Herein, we describe a triphenylpyrylium (TPT)-based visible...

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Published in:Polymer chemistry 2024-05, Vol.15 (18), p.1833-1838
Main Authors: Spicuzza, Michael, Gaikwad, Shweta Prakesh, Huss, Steven, Lee, Annemarie A, Craescu, Cristina V, Griggs, Anna, Joseph, Joshmi, Puthenpurayil, Mark, Lin, Wilson, Matarazzo, Christopher, Baldwin, Stanley, Perez, Victoria, Rodriguez-Acevedo, Diego Alejandro, Swierk, John R, Elacqua, Elizabeth
Format: Article
Language:English
Subjects:
Catalysis
Catalysts
Catalytic activity
Cations
Chains (polymeric)
Chemistry
Confinement
Crosslinking
Cycloaddition
Diels-Alder reactions
Naphthalene
Photoredox catalysis
Polymers
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Summary:Macromolecular scaffolds are rapidly emerging in catalysis owing to the ability to control catalyst placement at precise locations. This spatial proximity allows for enhanced catalyst activity that may not be observed using small molecules. Herein, we describe a triphenylpyrylium (TPT)-based visible-light active single-chain polymer nanoparticle (SCNP) that facilitates the radical cation [4 + 2]-cycloaddition. We find that the catalytic activity is highly dependent on the styrylarene comonomer used, wherein it can act as a redox mediator under confinement, increasing the catalytic turnover (TON) by up to 30 times in comparison to free TPT in solution. Mechanistic studies indicate that TPT excited states are quenched by the acene, with the resultant radical cation formed from naphthalene-based SCNPs able to proceed in oxidizing the dienophile in the elementary step of the reaction, while leading to near quantitative yields of the cycloadduct. The TPT-SCNP demonstrates enhanced photocatalyst efficiency compared to molecular TPT, and is able to be recycled and reused in three iterations of the reaction prior to decreased performance from photobleaching. Our results overall suggest that the confined nature of the SCNP and spatial proximity of acene-based pendants enforces their participation as cocatalytic redox mediators that impart enhanced photoredox catalysis under confinement. Single-chain polymer nanoparticle photoredox catalysts are designed wherein spatial proximity enables the crosslinking acene to act as a redox mediator, thus achieving up to 30-fold enhancement of catalyst activity in the model Diels-Alder reaction.
ISSN:1759-9954
1759-9962
DOI:10.1039/d4py00282b