Figure 9.

Computational models for the NO-ligated nonheme Fe_B site in ⁵⁷Fe^IINO-Fe_BMb1(Zn^II) using differing functionals yield quantitative predictions for the iron VDOS. Comparison with the experimental VDOS for ⁵⁷Fe^IINO-Fe_BMb1(Zn^II) in the presence of excess NO is consistent with a substantial contribution from NO-ligated iron. The red trace indicates the contribution from iron motion along the Fe–NO bond direction and highlights the variability of the predicted Fe–NO stretching frequency, which shifts from 376 cm^–1 using B3LYP to 454 cm^–1 using M06L. The image excludes hydrogen atoms.