Correlations between photoelectron and phosphorescence spectra of polycyclic hydrocarbons

Comparison of the first IP's obtained from the photoelectron spectra of polycyclic hydrocarbons with the phosphorescence bands and the p-, α- and β-bands in the absorption spectra shows that only the first IP's, the first p-bands and the first phosphorescence bands are related to each other. The first triplet level T can be calculated from the difference IP₁ ? E_t = T, where E_t is the energy of the first phosphorescence band. The first triplet level T approaches 4.9 eV which is the vertical IP of graphite. Any deviation from this value is strictly related to the number of aromatic sextets in polycyclic systems. This applies to kata- and peri-condensed hydrocarbons. The asymmetric annellation effects reported in earlier work are again supported by the phosphorescence spectra. Contrary to the observations with the α-, β- and p-bands, there is considerable interaction with the third branch in linear benzologues of triphenylene (starphenes) when the t-bands are formed, and the T level shifts towards higher energies (lower eV values).