Overlay plot of the isostructural Co, Ni, and Zn complexes (Amel'chenkova et al., 2006) with respect to the Fe complex (I). The coordinates of the Ni and Zn complexes have been inverted for this comparison. Hydrogen atoms are omitted for clarity. The quaternion fit algorithm (Mackay, 1984) as implemented in PLATON (Spek, 2009) was used for the preparation of the plot. Color scheme: Fe complex (blue),Co complex (green), Ni complex (red), and Zn complex (black).