Combination of its convenience for non-invasive application and high spatial resolution make Magnetic Resonance Imaging (MRI) one of the leading imaging modalities.
Intramolecular coordination of a linear copolymer precursor yields single chain nanoparticles (SCNP's) consisting of Pd(ii)-NHC2 crosslinks and showing a beneficial SCNP effect when used for the Suzuki coupling in water.
The intrinsic advantages of poly(ionic liquid)s (PILs), based on their high chemical activity and flexible structure, have been harnessed by exploring their applicability as catalytic single chain nanoparticles (SCNPs).
Owing to their broad modularity, polymeric versions of ionic liquids, referred to as poly(ionic liquids) (PILs), have attracted increasing attention as recyclable polymer-supported (pre)catalysts for various chemical transformations. Herein, an imidazolium-based statistical copolymer based on PIL (= coPIL) is specifically designed by free-radical copolymerization of styrene and 4-vinylbenzylethyl(benz)imidazolium chloride. A selective ion-exchange reaction can be subsequently achieved to incorporate bio-sourced difunctional sebacate-type counter-anions, causing the physical crosslinking of the coPIL precursor via electrostatic interactions between pendant imidazolium moieties and sebacate dianions. The as-obtained gel-type precursor exhibits a thermally latent behavior in THF, proving advantageous for a facile manipulation and practical use for organocatalysis. Upon heating, typically at 80 ºC, interaction between the sebacate dianion and the proton in C2-position of the imidazolium moieties generates polymer-supported N-heterocyclic carbene units that act as catalytic active species towards NHC-organocatalyzed reactions, namely, benzoin condensation, transesterification and cyanosilylation. The PIL-based gel precursors can be restored, recycled and reused by simply cooling down, i.e. with no need of an external chemical reagent, due to the shift of the intramolecular equilibrium towards the formation of imidazolium sebacatetype units. Overall, this novel gel-type copolymeric platform shows a thermo-responsive behaviour, and proves particularly versatile for heterogeneous organocatalysis.
The need for efficient, tailor‐made catalysts has inspired chemists to design synthetic macromolecular architectures for selective catalysis. To this purpose, herein the synthesis and in‐depth characterization of Ag(I)‐crosslinked single‐chain nanoparticles (SCNPs) is reported and their application as catalysts is demonstrated. Specifically, a copolymer of styrenic benzimidazolium chloride is synthesized as a linear precursor via reversible addition‐fragmentation chain‐transfer polymerization. Metalation of the benzimidazolium moieties by Ag(I) resulted in the intramolecular cross‐linking of single chains via the formation of silver‐N‐heterocyclic carbene (Ag‐NHC) linkages under dilute conditions. The successful formation of well‐defined, robust SCNPs is evidenced by size‐exclusion chromatography, dynamic light scattering, nuclear magnetic resonance spectroscopy, and transmission electron microscopy. Finally, it is demonstrated that the Ag‐SCNPs can be used as NHC pre‐catalysts, by first indirectly evidencing the formation of the corresponding unfolded NHC‐CS2 polybetaine and then organocatalysing a benzoin condensation reaction.
Front Cover: In article number 1900071, Rachel K. O'Reilly, Daniel Taton, Andrew P. Dove, and co‐workers report an intriguing, new type of single chain nanoparticle (SCNP) by the addition of silver atoms to linear precursors. Their subsequent catalytic performance as versatile nanoreactors could be easily switched on or off by inserting different anions or varying the temperature.
A self-catalysed folding strategy to form single chain nanoparticles (SCNPs) was developed via an intramolecular N-heterocyclic carbene (NHC)-mediated benzoin condensation.
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