Fig. 3: Minimum energy profiles (MEPs) for the photolysis of 1 producing the N-centered diradical 32 (np) and closed-shell singlet 12 (n2) along the reaction channels of the singlet and triplet states.
From: Generation and direct observation of a triplet arylnitrenium ion

The MEPs calculated at the CASPT2//CASSCF/PCM/cc-pVDZ level of theory, in which the line with red dots represents the SPP(1ππ*) state, the line with green dots represents the SCT(1πσ*) state, the line with orange dots represents the TNΣ(3nσ*) state and the line with black dots represents the S0 state. Selected stationary structures are given with their key bond (N–N) lengths in Å while the singly occupied molecular orbitals for the selective arylnitrenium ions are schematically provided. The value of 3.7 kcal/mol is the barrier required to be overcome to reach the CT(1ππ*/1πσ*) from the SPP(1ππ*)-Min, while the value of 4.2 kcal/mol is the barrier required to be overcome to arrive at the STC(3nσ*/S0) from 32 (np). The energy for each point in the MEPs and the structures for critical points are shown in the Supplementary Data File (FC Frank-Condon, STC singlet-triplet crossing; ISC intersystem crossing, CI = conical intersection).