Excitation Energies of Azulene and Naphthacene Triplets

Abstract

The high‐frequency phosphorescence emission previously attributed to naphthacene is found to be due to 5,12‐naphthacenequinone. Naphthacene triplets are not quenched by azulene although the latter is a good quencher for anthracene triplets. Consequently, we infer that the excitation energy of azulene triplets lies between 31 and 39 kcal/mole (11 000–14 000 cm⁻¹).