Nanosecond laser flash photolysis of 5-hydroxy-1,4-naphthoquinone (Juglone)

Abstract

The triplet properties of juglone, a monohydroxyquinone, were thoroughly investigated in cyclohexane, acetonitrile, methanol and isopropanol, by the technique of nanosecond laser flash photolysis. While the triplets absorb at about 285, 325 and 370 nm, the decay product, which absorbs at about 370 nm, is shown to be a neutral semiquinone free radical of juglone. The extinction coefficient for T-T absorption and the quantum yields of both triplet formation and semiquinone formation are estimated, and all the kinetic parameters associated with the triplet decay are evaluated. The effect of juglone concentration, laser intensity and the presence of triplet scavengers on the triplet properties were studied.