Overall, the bond lengths at all HF exchange fractions are either in very good or at least acceptable agreement with experiment except in select outlier cases. Following our analysis of bond lengths, we studied adiabatic spin splitting energies, (i.e., the differences in energy of DFT-optimized HS and LS states), as determined from the electronic energies, DEH-L, and with thermodynamically-corrected, Gibbs free energies, DGH-L (Figure ). ). We assign a prediction from a DFA as correct if it predicts the HS-LS splitting of a complex to be between -5.5 and +5.5 kcal/mol as all of these complexes have experimentally observed SCO behavior. Analysis of DEH-L values obtained at different levels of aHF reveals that modB3LYP with aHF = 0.15 correctly predicts 97% of the systems (i.e., 92 out of 95) to be SCO complexes based on this criterion (Supporting Information Figures S9-S10 and Table ). However, when the more experimentally relevant DGH-L is considered, the modB3LYP functional with a lower aHF (0.10) correctly predicts the highest number, 93% of the systems (i.e., 88 out of 95), to be SCO compounds, at odds with some earlier work on representative SCO complexes 108,154 that favored a higher aHF = 0.15 value (Figure and Supporting Information Figure and Table ). The computed DGH-L values for the SCOs exhibit a few consistent outliers at all values of aHF (refcodes: ECODIM 155 , WIHQIQ 156 , YAGYUB 157 , and ZERDOS 158 ) of which some (refcodes: WIHQIQ and YAGYUB) have a slightly stronger preference for HS states while the others (refcodes: ECODIM and ZERDOS) tend to prefer LS states (Figure and Supporting Information Figure ). However, experimental SCO behavior was reported for crystal structures of all these identified outliers . It is worth noting the diverse chemical composition of these outliers: the homoleptic SCO WIHQIQ has six Fe-S bonds and the ligands of homoleptic YAGYUB contain iodine, while both heteroleptic ECODIM and ZERDOS complexes contain boron (Supporting Information Figure ). These more varied compositions could cause these predictions to benefit less from error cancellation in HF-exchangetuned functionals in comparison to more conventional Fe(II)/N complexes. The bin width in these plots is 2.5 kcal/mol. The solid gray lines represent zeroaxes in all the plots. A representative SCO complex (REFCODE: ACAHUJ) is shown in the inset and the bin that contains its property value is marked with a red star in each pane. Hydrogen, carbon, nitrogen, oxygen, and iron are shown in white, gray, blue, red, and brown, respectively.