As mentioned above, the binding mechanism of Zr 4+ to the chelators in water will naturally involve solvation and de-solvation processes. Several of the previous DFT-based calculations have shown, by the inclusion of a few coordinating water molecules, that specific interactions with the solvent can be an important determinant in binding. To understand the role of the solvent, we examined the water coordination around Zr 4+ for both the DFO and 4HMS chelation complex.