DFT study of two-photon absorption of octupolar molecules

The two-photon absorption (TPA) properties of octupolar molecules based on a triphenyl-isocyanurate cyclotrimer, a 1,3,5-triphenyl-benzene or a triphenyl-triazine core were theoretically investigated using DFT and TD-DFT computations. These compounds are very promising regarding their potential application, especially for optical limitation. These systems, which exhibit a threefold axis, contain three arms with a terminal electron-donating group linked in 1, 3 and 5 positions to the central C3N3O3 isocyanurate, benzene or triazine ring. The SAOP functional and a DZP basis set were selected for the TPA computations. The so-computed TPA energies and cross sections are in good agreement with the observed data. Increasing the strength of the donor terminal group enhances the TPA cross section values. The compound with triazine core presents the highest two-photon cross section value compared to the values found for the isocyanurate or the 1,3,5-phenyl core as central ring. Furthermore, this study brings to light a cooperative enhancement of the TPA property between the three arms attached to the isocyanurate ring.