and). The DFT MAE on the test set with outliers removed is highest at 512 K for TPSSh and lowest for M06-L at 162 K (Figure and Supporting Information Table ). Despite this better overall performance of M06-L, the larger spread in values from the modB3LYP (aHF = 0.10) and TPSSh functionals leads to them exhibiting a better Pearson's r and Spearman's r relative to M06-L, i.e., ca. 0.50 for TPSSh or B3LYP vs 0.25 for M06-L (Figure and Supporting Information Table ). Further examination reveals that modB3LYP (aHF = 0.10) and TPSSh predictions have extreme outliers (refcodes: OSABOB 131 and UXOHEW 127 ) resulting in very large MAE values (Figure ). While the DFA-predicted T1/2 values show MAE of up to ca. 500 K vs an MAE of 40 K observed for best-performing ML models, their