Electrochemiluminescence of Energy‐Deficient Systems II. The Role of Excimer Formation in the Pure Perylene System

Abstract

AbstractThe reaction enthalpy Δ H of the chemiluminescent electron‐transfer reaction between perylene radical cations and anions has been estimated from electrochemical measurements. The comparison of H with the energies of the excited states of perylene leads to the conclusion that excited singlet molecules, the emission of which is observed, cannot be formed directly; rather excited triplets are produced in the electron‐transfer reaction which yield excited singulets via triplet‐triplet annihilation. This mechanism is confirmed by the analysis of the ecl intensity‐time curves. The long‐wavelength component occuring in the ecl spectrum of perylene is ascribed to excimer emission in agreement with the experimental results. These suggest the assumption that the intensity ratio of the long‐wavelength component to the fluorescent component is determined by the fact that perylene triplets—dependent on electrolysis time ‐ are quenched by excess radical ions in the reaction zone; the excimers, however, are not.