Figure 10.

Two plausible excited state mechanisms of Ni(II)─C bond homolysis. Initial ¹(d-d) or ¹MLCT excitation (blue or orange boxes, respectively) is followed by ISC and ³LMCT formation. On the right, this surface hopping mechanism is exemplified with the shaded purple circles connecting the ¹(d-d) excited-state surface (purple line) to the one-electron triplet repulsive ³LMCT surface (green line), or ¹MLCT excited-state surface (blue line) to the two-electron triplet repulsive ³(MLCT+LMCT) surface (red line). Corresponding plots computed at the TD-DFT and CASSCF/QD-NEVPT2 levels are provided in Figures S68-69. For clarity, exchange splitting between α and β orbitals is neglected. Illustrative orbital energies and ordering on the left are provided from the ground state and are held constant through steps 1-4; right panel gives a more accurate depiction of relative state energies, reflecting a small thermal barrier relative to the excitation energy.