Dimethylsulfoxide as a kinetic booster for the chemical generation of singlet oxygen in methanol

The kinetic booster effect of dimethylsulfoxide on the chemical generation of singlet oxygen, 1O2, from the disproportionation of hydrogen peroxide catalyzed by molybdate ions in methanol has been evidenced by detection of the IR luminescence of 1O2 at 1270 nm and by 95Mo NMR spectroscopy. DMSO interacts rapidly, through a direct oxygen transfer with the stable tetraperoxomolybdate Mo(O2)42-, leading to DMSO2 and to the unstable triperoxomolybdate Mo(O2)32-, which releases 1O2. The procedure was applied to accelerate the dark singlet oxygenation of β-citronellol and α-terpinene.