The excited state calculations show that the calculated average ΔELE-CT of DAAPC/2-PPT (68 meV) is much smaller than that of DAAPC/2.8-PPT (255 meV) and DDATA/2.8-PPT (492 meV) (Fig. , Supplementary Table ). This is consistent with the experimental evidence that DAAPC/2,8-PPT has a small ΔELUMO. The natural transition orbitals of all systems show that the lowest singlet excited state (S1) can be identified predominantly as the PPT, owing to hybridization between CT and LE states in the S1 states (Fig. and Supplementary Table ).