Absorption Spectra of Dianthracene Anion Radical and Anthracene Dimer Anion

Abstract

Dianthracene in γ‐irradiated rigid ethereal solutions at 77°K reacts with mobile electrons produced by ionization to give a pair of anthracene molecule and anion which interact weakly to constitute a dimer anion. The dimer anion exhibits spectral features of (i) an extra intermolecular charge resonance band in the near infrared region, (ii) hypochromism in comparison to the free anthracene molecule and anion. The observed spectrum of the dimer can be well accounted for by molecular orbital calculations with the assumption of a sandwich structure for the dimer. In contrast to the mobile electron the matrix‐trapped electron which has less kinetic energy reacts with dianthracene only to give dianthracene anion radicals which show doublet charge resonance bands in the near‐infrared region. The anion is unstable both thermally and optically, and splits to an anthracene molecule and an anion via the dimer anion.