Figure 6.

Structures (S) S1–S4 (see Table 2): the central portions of the optimized geometries after removing the H-bonding H₂O molecule from the Fe_a3^HS,3+–H₂O–Cu_B(a–d) structures (see Figure 4V–VIII). S5 is a constrained geometry optimized structure with a fixed Fe–O distance at 2.39 Å. (A) and (B) show the overlap of S1–S5 with the X-ray crystal structure 3S8G in two different viewing angles (see also Figure 7).