where CN is the coordination number of a given complex, d(M -A i ) represents the distance between a metal center (M) and a coordinating atom (A i ), and r M and r A i are covalent radii of M and A i , respectively. Covalent radii values were taken from a previous analysis of experimental crystal structures (Table in the SI). Figure shows the distribution of relative metal radii and their corresponding ground state spins for Fe(II) complexes depending on the coordination geometry. Across different coordination geometries, Fe(II) complexes in the HS state typically possess longer relative metal radii compared to those in the LS or IS states. In general, we observe a biased distribution toward HS states with longer relative metal radii. In particular, the relative metal radii of octahedral Fe(II) complexes show a binomial distribution, separating LS and HS. Interestingly, two tetrahedral Fe(II) complexes with LS state exhibit very short relative metal radii, which deviate from the overall distribution of relative metal radii in tetrahedral complexes. This suggests that relative metal radius serves to identify outliers exhibiting uncommon ground state spins. Moreover, there is a systematic increase in relative metal radius as the coordination number increases. This pattern is especially evident in HS complexes, which display a linear increase, as shown in Figure in the SI.