In 2010, Tian et al. examined the performance of global hybrids (PBE0, B3LYP, M06, M06-2X, M06HF) and long-range corrected (LC) hybrid functionals (ωB97X-D, ωB97X, ωB97, LC-ωPBE and CAM-B3LYP) in TD-DFT calculations to predict the spectral properties of PP analogues. Among the many functionals tested, the LC functional ωB97X-D results in an error of 0.05 eV for Qy band. Moreover, they concluded that the results are robust with respect to subtle geometry changes resulting from the functional choice for geometry optimization and showed that diffuse functions have only a minor effect on calculated absorption spectra.