Electronic spectroscopy of highly polar aromatics. XI. Luminescence of the cyanoanilines

The absorption and emission spectra of the three isomeric cyanoanilines have been investigated. Quantum yields and decay lifetimes are reported for both fluorescence and phosphorescence processes. It is shown that the lowest energy absorption band of p-cyanoaniline consists of two distinct electronic transitions of the ¹π^*←¹π type, whereas, in the o- and m-cyanoanilines, the lowest energy absorption band consists of a single electronic transition of the ¹π^*←¹π type. These conditions are consistent with absorption data, emission data and kinetic analyses. The largest ?_P/?_F ratio is exhibited by the p-cyanoaniline and this observation is rationalized.