Covalent Immobilization of (-)-Riboflavin on Polymer Functionalized Silica Particles: Application in the Photocatalytic E→Z Isomerization of Polarized Alkenes.

The covalent immobilization of the biomimetic, photo-organocatalyst (-)-riboflavin on silica micro- and nanoparticles via atom transfer radical polymerization (ATRP) is disclosed. Given the effectiveness of (-)-riboflavin as a versatile, environmentally benign photocatalyst, an immobilization strategy based on acrylate-linker modification of the catalyst core and controlled polymerization on initiator pre-functionalized silica particles has been developed. Validation of this approach is demonstrated in the E→Z isomerization of a benchmark cinnamonitrile (Z/E up to 88:12) with 0.97 mol % catalyst loading. Characterization of the immobilized photocatalyst supports covalent embedding of the catalyst in the polymeric brushes on the silica particle surface.

Self-assembly of colloidal molecules that respond to light and a magnetic field.

This communication reports a novel method to prepare Janus particles with light-responsive arylazopyrazole (AAP) polymer caps, which can be reversibly cross-linked to chain-like colloidal oligomers in the presence of cyclodextrin (CD) functionalized superparamagnetic nanoparticles. The resulting colloidal molecules are light-responsive and can be controlled by an external magnetic field.