Light-Induced Polymeric Frustrated Radical Pairs as Building Blocks for Materials and Photocatalysts

Abstract

Polymeric frustrated Lewis pairs, or poly­(FLP)­s, have served to bridge the gap between functional polymer science and main group catalysis, pairing the uniqueness of sterically frustrated Lewis acids and bases with a polymer scaffold to create self-healing gels and recyclable catalysts. However, their utilization in radical chemistry is unprecedented. In this paper, we disclose the synthesis of polymeric frustrated radical pairs, or poly­(FRP)­s, by in situ photoinduction of FLP moieties, where their Lewis acidic and basic centers are tuned to promote single electron transfer (SET). Through systematic manipulation of the chemical structure, we demonstrate that inclusion of ortho-methyl groups on phosphine monomers is crucial to enable SET. The generation of radicals is evidenced by monitoring the stable polymeric phosphine radical cations via UV/vis and EPR spectroscopy. These new poly­(FRP)­s enable both catalytic hydrogenation and radical-mediated photocatalytic perfluoroalkylations. These polymeric radical systems open new avenues to design novel functional polymers for catalysis and photoelectrical chemistry.

p-Diarylboryl Halothiophenols as Multifunctional Catalysts via Photoactive Intramolecular Frustrated Lewis Pairs

“…This mode of SET, in principle, generates a radical pair consisting of a Lewis base radical cation and Lewis acid radical anion, which can engage in a chemical transformation. Accordingly, in parallel with the understanding of the SET process, the distinct reactivity and selectivity of radical pairs have garnered increasing attention and have gradually been applied in synthetic chemistry for the generation of reactive radical intermediates to promote molecular transformations using stoichiometric amounts of Lewis pairs . Under these circumstances, we demonstrated the ability of tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) to act as a redox catalyst spontaneously or under light irradiation for carbon–carbon bond-forming reactions .…”

Synthesis and Properties of Cyclic π-Conjugated Molecules and Their Dication and Monoradical Cation

“…Radical species are important intermediates of various organic reactions, such as dimerization, cationic polymerization, azo formation, nucleophilic substitution, and proton transfer reactions, , and functional materials, owing to their unique electronic properties . However, radical species are generally unstable, their lifetime is short, and they can be coupled with other radical species, and thus it is necessary to stabilize them for practical use.…”