Energy of Excimer Luminescence. V. Excimer Fluorescence of Naphthalene and Methylnaphthalenes

Abstract

The interpretation of the energies of excimer luminescence of naphthalene and 12 of its alkyl derivatives is considered, and it is shown (i) that there is considerable configuration interaction between molecular-exciton and charge-resonance states and (ii) that the energy of excimer fluorescence may not be interpreted without invoking this configuration interaction. Excimer-fluorescence energies are calculated for the substituted naphthalenes using a four-electron MO treatment of the interaction and as a function of Z, the Slater orbital effective charge exponent, and of the interplanar distance D. Agreement with excimer-luminescence energies is obtained for values of Z=3.18 and values of D between 3.4 and 3.7 Å, with the largest intermolecular distance D being obtained for those compounds in which steric hindrance is expected to be largest.