Optical absorptions of new blue-light emitting oligoquinolines bearing pyrenyl and triphenyl endgroups investigated with time-dependent density functional theory

The optical absorption spectra of a family of four n-type conjugated oligomers, oligoquinolines, which can be commercially used to develop high-performance light-emitting diodes for their many desirable properties, have been recently calculated from time-depedent density functional theory (TDDFT) within the adiabatic approximation for the dynamical exchangecorrelation potential. In this work, we investigate the optical absorption of two new family members of the blue-light emitting oligoquinolines bearing pyrenyl and triphenyl endgroups in gas phase and chloroform (CHCl3) solution employing the adiabatic TDDFT. The ionization potentials and electron affinities of these two oligoquinoline molecules are also calculated with the groundstate DFT, from which the adiabatic dynamical exchange-correlation potential is constructed. We show that the calculated optical absorptions are in good agreement with experiments. The ionization potentials obtained with the DFT methods agree well with the experimental estimates, while the electron affinities are significantly underestimated in comparison with experiments. A natural transition orbital analysis for selected excited states with the largest oscillator strengths shows that the electronic charge is slightly redistributed in the process of electronic excitations.