A comparative study of the electronic structure and spectra of tetraoxa[8]circulene and octathio[8]circulene

Abstract

The electronic structure and spectra of two highly symmetric molecules of circulenes, namely, tetraoxa[8]circulene and octathio[8]circulene, which belong to the symmetry point groups D4h and D8h, respectively, have been investigated by the density functional theory (DFT) method using the hybrid functional B3LYP in the 6–31G(d) basis set. The infrared (IR) spectra of these molecules in the ground and excited triplet states have been compared. The comparison of the electronic absorption spectra of both molecules has revealed that the first electronic transition is forbidden and determined by the electronic-vibrational interaction due to the degenerate eu modes. The ability of the studied circulenes to fluoresce and phosphoresce has been analyzed, because these compounds are of interest as promising materials for organic light-emitting diodes.