DFT Calculations. DFT geometry optimizations were performed without simplifications on full atomic models using TURBOMOLE 7.5.1, 26 coupled to the PQS Baker optimizer, via the BOpt package. All calculations were performed in the gas phase with convergence criteria (scfconv = 7) on a m4 grid and Grimme's version 3 zero-damping dispersion corrections to compensate for the underestimation of metal-ligand interactions from uncorrected DFT calculations. Geometry optimizations were performed at the ri-DFT BP86 31 /def2-TZVP 32 level of theory. All minima, without imaginary frequencies, were characterized by calculating the analytical Hessian matrix. Energy output generated in Hartree units was converted to kcal/mol by multiplication with 627.51. Graphical representations of orbitals are obtained using IboView 33 and visualization of spin densities using IQMol. Synthesis of [Co III (TPP)Cl]. [Co III (TPP)Cl] was synthesized according to a literature procedure. [Co II (TPP)] (300 mg, 0.44 mmol, 1 eq) was suspended in MeOH (300 mL) and HCl (3 mL, 12 M) was added dropwise. The purple suspension was stirred for 3 hours without a stopper on the flask. The red solution was filtered and the filtrate was concentrated in vacuo until a green precipitate was formed. It was filtered and washed with H2O (100 mL) and MeOH:H2O 1:1 (30 mL). The purple powder was dried over P2O5 overnight and stored in the glovebox immediately after. Purple powder (92%). 1 H NMR (300 MHz, Methylene Chloride-d2) δ 8.81 (br s, 8H), 8.23 (br s, 8H), 7.80 (br s, 12H). UV-Vis (CH2Cl2) λmax 405 nm and 543 nm.