Solvent-Free Production of Singlet Oxygen at the Gas-Solid Interface: Visible Light Activated Organic-Inorganic Hybrid Microreactors Including New Cyanoaromatic Photosensitizers

We synthesized new cyanoaromatics, benzo[b]triphenylene-9,14-dicarbonitrile (DBTP) 1a and a graftable derivative, 9,14-dicyanobenzo[b]triphenylene-3-carboxylic acid (DBTP-COOH) 1b, easily prepared from commercial reagents. Their photosensitizing properties were investigated. Hybrid porous silica monoliths loaded with encapsulated la or grafted 1b were prepared, and their adsorption, spectroscopic and photosensitizing properties, as well as stability, were compared. Solvent-free, efficient oxidation of dimethylsulfide (DMS) was observed at the gas-solid interface Under visible light irradiation. Quantum yields of formation of O-1(2) inside the porous monoliths are comparable to those of phenalenone. Singlet oxygen lifetimes (similar to 25 mu s) were found to be longer in silica monoliths than in usual polar solvents such as methanol or ethanol. This new class of hybrid materials work as porous, transparent, and highly efficient microreactors for oxidation reactions under visible light.