Diffuse reflectance laser photolytic studies of pyrene included in zeolites - Formation of pyrene anion radicals via excited-state electron transfer between guest molecules

The formation of pyrene radical anions was observed on photo-excitation of pyrene as a result of electron transfer between pyrene molecules in the excited state and those in the ground state. This conclusion is based on the observation of concentration-dependent quenching of pyrene monomer fluorescence accompanied by a concomitant rise in the transient absorption bands of pyrene radical cation and pyrene radical anion. The present observation is significantly different in mechanism from a previous investigation in which the radical anion was found to be produced by the photo-electron transfer from host alkali metal-exchanged zeolites to excited pyrene.