Thus, the adiabatic electron affinity (EAa) of K[TDC] (with a redox-inactive K + ion at its core) turned out to be 1.9 eV, far higher than that of a typical electronically innocent metalloporphyrin, which typically hover around 1.2-1.3 eV. The electronic descriptions of the ionized states of Co[TDC] appear to much more straightforward relative to that for neutral state. The lowest-energy cation (denoted C1) is a straightforward low-spin Co(II) species with a dz2 1 electronic configuration, with a dp description, with the Ni(I) state about 1 eV higher in energy. In this respect, Ni[TDC] does not mimic cofactor F430 as well as ligands such as iaobacteriochlorin, oxaporphyrin, and thiaporphyrin, which stabilize the Ni(I) state. Remarkably, the B,Ctetradehydrocorrin ligand also appears to differ from Ni corrin and other Ni dehydrocorrins, which are thought stabilize an Ni(I) state. Our calculations also indicate unambiguous ligand-centered oxidation and reduction. Thus, the {Ni[TDC]} + cation is a straightforward, low-spin Ni(II) species, whereas the anion is clearly describable as Ni II -L 3-. For both ionized states, the triplet states are significantly higher in energy relative to the singlet ground states. Bottom right: canonical MO best described as SOMO.