Visible-light photocatalysis promoted by solid- and liquid-phase immobilized transition metal complexes in organic synthesis

• Recovery and reuse of photocatalysts. • Immobilization of photoredox catalysts on solid support. • Conception of homogeneous reusable catalysts for visible light-driven organic reactions. • Positive effects of solid supports on photocatalytic reaction. • Continuous flow photoreactions in the presence of reusable photocatalysts. This review summarizes synthetic approaches to reusable photocatalytic systems based on visible light-active transition metal complexes with chelating ligands containing pyridyl residues such as 2,2′-bipyridines, 1,10-phenanthrolines, 2,2′:6′,2′′-terpyridines and related ligands. The use of these materials in organic synthesis is then discussed focusing on 1) most active systems exhibiting a synergy effect between photophysical properties of immobilized complexes and photoactive solid supports and 2) reusability of the developed catalytic system.