Table . Electronic energy differences, binding enthalpies, binding Gibbs free energies, and interatomic distances for various M I M II 4Cl3(bta)6 cluster models. The M I -H2 distances were measured between M I atom and a point in the middle of the H2 bond. The M II atom refers to the central metal ion, and the M I atom refers to the peripheral metal ion. With the obtained optimized geometry, we then performed H2 binding enthalpy estimations. We found that the choice of the peripheral M I ion can cause a drastic change in the adsorption enthalpy for a given central M II ion, whereas the choice of the central M II can further tune the adsorption enthalpy for a given peripheral M I site. As expected from comparison of Cu I M4Cl3(bta)6 clusters, a larger central M II generally leads to weaker H2 adsorption enthalpy, although the magnitude of tunability varies depending on the peripheral M I ion. The degree of enthalpy change saturation with the change of the central ion is also highly dependent on the identity of the M I atom. Thus, Cu I and Ag I show greater tunability with high magnitudes of enthalpy variation when transitioning from Mn II to Cd II central atoms, while Co I and Ni I demonstrate lesser changes in enthalpy. Faster saturation for the Ni I case could also be inferred from the degree of π-backdonation, as can be seen from the H-H bond activation. A large H-H bond change of 7 pm is observed when the ionic radius of the central atom changes from 74 pm for Zn II to 83 pm for Mn II , while the transition from 83 pm for Mn II to 95 pm for Cd II led only to a marginal change of 2 pm in the H-H bond.