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

Metternich J, Sagebiel S, Lückener A, Lamping S, Ravoo BJ, Gilmour R

Abstract

Abstract 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.