Molecular Photothermal Conversion Catalyst Promotes Photocontrolled Atom Transfer Radical Polymerization.

Photothermal conversion is a growing research area that promotes thermal transformations with visible light irradiation. However, few examples of dual photothermal conversion and catalysis limit the power of this phenomenon. Here, we take inspiration from nature's ability to use porphyrinic compounds for nonradiative relaxation to convert light into heat to facilitate thermal polymerization catalysis. We identify the photothermal conversion catalytic activity of a vitamin B12 derivative, heptamethyl ester cobyrinate (HME-Cob), to perform atom transfer radical polymerization (ATRP) under irradiation. Rapid polymerization are obtained under photothermal activation while maintaining good control over polymerization with the aid of a photoinitiator to enable light-induced catalyst regeneration. The catalyst exhibits exquisite temporal control in photocontrolled thermal polymerization. Ultimately, the activation of this complex is accessed across a broad range of wavelengths, including near-IR light, with excellent temporal control. This work showcases the potential of developing photothermal conversion catalysts.

Vitamin B12 Derivative Enables Cobalt-Catalyzed Atom Transfer Radical Polymerization.

Advances in controlled radical polymerizations by cobalt complexes have primarily taken advantage of the reactivity of cobalt as a persistent radical to reversibly deactivate propagating chains by forming a carbon-cobalt bond. However, cobalt-mediated radical polymerizations require stoichiometric ratios of a cobalt complex, deterring its utility in synthesizing well-defined polymers. Here, we developed a strategy to use cobalt as a catalyst to control radical polymerizations via halogen atom transfer with alkyl halide initiators. Using a modified, hydrophobic analogue of vitamin B12 (heptamethyl ester cobyrinate) as a cobalt precatalyst, we controlled the polymerization of acrylate monomers. The polymerization efficiency of the cobalt catalyst was significantly improved by additional bromide anions, which enhanced the deactivation of propagating radicals yielding polymers with dispersity values <1.2 using catalyst concentrations as low as 5 mol %. We anticipate that the development of cobalt catalysis in atom transfer radical polymerization will enable new opportunities in designing catalytic systems for the controlled synthesis of polymers.

Development and application of a high throughput assay system for the detection of Rieske dioxygenase activity.

Herein we report the development of a new periodate-based reactive assay system for the fluorescent detection of the cis-diol metabolites produced by Rieske dioxygenases. This sensitive and diastereoselective assay system successfully evaluates the substrate scope of Rieske dioxygenases and determines the relative activity of a rationally designed Rieske dioxygenase variant library. The high throughput capacity of the assay system enables rapid and efficient substrate scope investigations and screening of large dioxygenase variant libraries.