Photochemical and sonochemical reactions of norharmane

In this work, a study on the photochemical and sonochemical behaviour of norharmane in halomethane media (dichloromethane, chloroform, carbon tetrachloride and dibromomethane) is presented. When solutions of norharmane in these media are irradiated with UV light or sonicated with ultrasound at 20 or 50 kHz, the cationic species of norharmane appears in solution. In order to explain the formation of this species by a UV radiation effect, a exciplex (charge transfer complex) between norharmane and halomethane has been proposed. The formation rate constants of the exciplex were calculated using fluorescence quantum yields and lifetime values. The sonochemical formation of cationic species does not occur by formation of a charge transfer complex between norharmane and halomethane. In this paper, we report that an initially neutral medium can quickly develop acidity in a few minutes of exposure in a conventional bath to ultrasound.