Azulenium cations. An experimental and theoretical study of the cations derived from hydrocarbon derivatives of azulene

Abstract

The ambient temperature ultraviolet absorption and the 77 K luminescence spectra of a series of four hydrocarbon derivatives of azulene in sulfuric acid solution are presented and discussed in detail. CNDO/S calculations have been carried out and the calculational results are compared with the experimental results. The phosphorescences of these cationic species are reported for the first time. The present results suggest that an inversion in the order of electronic states is perhaps responsible for the normal emissions of the protonated species and the anomalous emissions of the parent molecules.