Figure 11.

Computed excited state activation energies (TD-DFT, top; CASSCF/QD-NEVPT2, bottom) for 1A–5D plotted against experimental ln(k_obs,1) obtained using 390 nm excitation. Note that for 1A, k_1,obs is approximated by k_2,obs. The activation energies are estimated from the surface crossing between the high-energy ¹MLCT [d(yz) → π*(2)] PES and the ‘one-photon, two-electron’ triplet repulsive surface, ³(MLCT+LMCT) (more details can be found in Supporting Information Section S2.2; see Figure S66 for an analogous plot with the ‘one-photon, one-electron’ triplet repulsive surface). Additionally, we have found an activation energy of ~2.2 kcal mol⁻¹ for 1B–Br complex, which is in an excellent agreement with the experimental ΔH^‡.