Indigo chemiluminescence

Indigotin in basic solutions of polar aprotic solvents reacts with atmospheric oxygen yielding isatin. The reaction is accompanied by emission of light with a quantum yield equal to 2.6×10^?4 Einstein/mol. The spectral distribution of the indigotin chemiluminescence is that of the isatin fluorescence. Addition of equimolar amounts of isatin to the reaction mixture raises the chemiluminescence quantum yield to 5.3×10^?4 Einstein/mol. A mechanism involving the intermediate formation of indigotin dioxetan is proposed.