Figure 5.

The correlations between (a) $\left|{\sigma }_p\right|$ and the excitation energies of the S₁ and T₁ states, (b) $\left|{\sigma }_p\right|$ and S₁-2T₁ energy gap and HOMO-LUMO gap, and (c) ${\sigma }_p$ and HOMO and LUMO energies. We took the corresponding energies or energy gaps of PEN (E_PEN or ΔE_PEN) as the standards, and we plotted E_PEN − E in (a,c), whereas ΔE − ΔE_PEN in (b) for clarity. The dotted approximate line shows the general trends of ${\sigma }_p$ and several energies.