By focusing on the high-symmetry system with R = H, (Fig. ) these questions are addressed by partitioning free-base subporphyrin monoanion as the 𝒮 3 ℬ 1 class (Fig. ). The "subporphyrindiyl" fragment 5 (Fig. ), the monoanion without the inner hydrogen atom, exhibits the D3h symmetry point group from an atom-connectivity configuration perspective. Under the condition of non-dissociation to maintain a single molecular entity, a full connectivity permutation between the three sites (N-atoms) and the single bonder (H-atom) gives the seven species as shown in Fig. .