Auto-tandem PET and EnT photocatalysis by crude chlorophyll under visible light towards the oxidative functionalization of indoles

Chlorophyll is the most abundant photocatalytic pigment that enables plants to absorb solar energy and convert it to energy storage molecules. Herein, we report a tandem photocatalytic approach utilizing the natural pigment chlorophyll in crude form to achieve photoinduced electron transfer (PET) and energy transfer (EnT) towards the oxidative functionalization of indoles. Redox potentials, ESR, fluorescence quenching and UV experiments have evidenced the dual catalytic activity of chlorophyll. The highlight of the study is the auto-tandem photocatalytic role of chlorophyll to enable the green oxidation of indoles using molecular oxygen as the oxidant, water as the reaction medium, and photochemical energy from the visible region of the spectrum. A greener approach towards oxidative functionalization of indoles under visible light employing the PET and EnT capabilities of crude Chl, air as oxidant and water as solvent has been developed.