Extended Data Fig. 1: Computational studies to estimate reorganization energy.
(a) Tanabe-Sugano diagram appropriate for [Co(pyrro-bpy)3](PF6)3 based on the ligand-field analysis described in ref. 29. The diagram was constructing using the experimentally determined Racah B and C parameter values of 480 cm-1 and 3430 cm-1, respectively. The vertical dashed line corresponds to the value of 10 Dq found for [Co(pyrro-bpy)3](PF6)3. It should be emphasized that these diagrams reflect vertical transition energies, not the zero-point energy of a given excited state that ultimately determines which state lies lowest in energy. Inset: An expanded view of the region near the crossing point between the 5T2 and 3T1 ligand-field excited states. (b) Comparison between time-resolved absorption spectra obtained from a singular value decomposition analysis of the experimental transient absorption data and TD-DFT-computed excited-state absorption spectra for the structurally relaxed, lowest-energy S=1 (3MC) excited state. Inset: Spin density associated with the 3MC ligand-field excited state derived from DFT calculations carried out at the optimized equilibrium geometry, showing localization of the spin density predominantly on the metal center. Positive (excess α) and negative (excess β) spin density contributions are shown as green and orange isosurfaces, respectively (isovalue = 0.003). (c) DFT-predicted 1A1→1ES (pink) and 1A1→3MC (blue) vertical transition energies compared with their experimentally determined values (dashed lines). The black triangles at the bottom of the plot correspond to the energy difference between triplet energy at singlet optimized geometry and triplet optimized geometry (black triangles) as a function of % HF exchange.
