Results obtained from gas phase calculations are shown in Table . When measuring the relative stabilities of the different clusters proposed, we find a tendency towards favouring clusters with a higher number of acetate ligands. This trend is related to the expected propensity to neutralize the charge in the gas phase. Interestingly though, the most stable clusters are not those with the highest possible number of acetates (i.e., four ligands). Instead, the most stable clusters contain three acetate ligands and a single imidazole (i.e., [Zn(Im) 1 (Ac) 3 ] -). This tendency is captured for tetrahedral and octahedral clusters, and agree with the results obtained by Dudev and Lim . In their work, they proposed the q + 1 rule, which states that the most stable coordination of a metal with a given charge q, is that formed by q + 1 monodentately bound Glu/Asp (in our case represented by the acetate moiety). Additionally, in Table we show results obtained when comparing relative stabilities between tetrahedral and octahedral geometries for each cluster. Results from the first coordination shell approach (FCS) and the alternative where we consider of two additional water molecules (FCS+2W, see Methods) point in different directions. On one hand, in the FCS approach, ∆∆H T/O energies show that octahedral coordination is favored, whereas ∆∆G T/O energies show that tetrahedral coordination is favored. However, after introducing the correction in ∆∆G T/O to obtain ∆∆G T/O 1/2 energies, the latter also show that octahedral geometries are favored for all clusters. We should replace this in the gas phase, with the exception of the [Zn(Im) 4 ] 2+ cluster. Conversely, if the FCS+2W approach is considered, both ∆∆H T/O and ∆∆G T/O energies point to tetrahedral coordination as the one favored in the gas phase. It is noteworthy that as mentioned, the FCS+2W approach overestabilizes tetra-hedral coordination. Nevertheless, if this overestabilization is calculated and energies are recalculated taking the overestabilization into consideration (see Table ), we see that both the ∆H and ∆G terms of the FCS and FCS+2W approaches are now extremely similar. The FCS+2W predicts a preference for tetrahedral arrangements in the gas phase, which is believed to be caused by the overestabilization introduced by the water molecules present in the second coordination shell.