Interestingly, for clusters with mIm -ligands, the situation is reversed, with the 4MR-SOD cluster being more stable than 4MR-zni (see Table ). This reversal in stability might be related to the repulsions between the methyl groups of the mIm -ligands, which in mIm-4MR-zni clusters are pointing in opposite directions, thus increasing the repulsions between the groups (see Figure ), with respect to the mIm-4MR-SOD cluster (Figure ). Note that in the Im-4MR-zni cluster, one imidazole group is rotated, to increase the distance between the H atoms (Figure ). This increase in H-H distance to reduce repulsions induces an increase in Zn-Zn distances, in both the mIm-based clusters and crystal structures, since the distance between first neighbor Zn atoms is 6.1 Å in both 4MR and 6MR mIm -clusters, which is similar to that of the SOD crystal structure, but larger than that of the Im-based zni crystal structure (5.85 Å). The dihedral angles in the 6MR clusters are ∼ 0 • (as in the SOD structure) for both Im -and mIm -clusters, explaining why both ligands can form ZIFs with 6MRs in their topologies.