Laser-induced formation of pyrenyloxy radical from 1-hydoxypyrene and further oxidation: Micellar effects

Laser photolysis of POH was investigated in aqueous ethanol, three organic solvents with different polarity, SDS micellar and AOT reverse micellar solutions. The analysis of the laser-induced transient absorption (TA) spectra showed that the pyrenyloxy radical (PO) was formed via a prompt deprotonation from the cation radical (POH)+. The observed micellar effects on the formation of the pyrenyloxy radical were consistent with this mechanism of formation. Based on the shift as well as the intensity of the TA peak attributable to the pyrenyloxy radical, information on the microenvironment surrounding POH (i.e., hydrophobic or hydrophilic, contact or no contact with water phase) was obtained. The secondary photochemical reaction after laser irradiation was investigated with UV/vis absorption spectroscopy. 1,6- and 1,8-pyrenediones were found to be produced as the main photoproducts.