Figure 3.

4.2 K Mössbauer spectra of the H200C–HPCA complex recorded in parallel applied fields indicated. Simulated spectra of two unknown Fe^III contaminants, shown in Figure S1 and representing ≈ 15% of the Fe, were subtracted from the raw data. The red lines, representing 85% of total Fe, are spectral simulations based on eqs 1 and 2 using the parameters listed in Table 1. Simulations were performed in the slow relaxation limit of the electronic spin.