Interestingly, for the case of Zr 4+ -4HMS at distances less than 3.0 Å, the ion appears to be equally coordinated to four oxygen atoms from 4HMS and four oxygen atoms from surrounding water molecules (see a representative snapshot from simulations bottom right panel of Fig. )). Similar to DFO, the reduced coordination from the chelator hydroxamate groups originates from the fact that, unlike at 0-K, the oxygen atoms of the hydroxamate groups do not symmetrically coordinate the ion which subsequently leads to differences in the Zr 4+ -O-N and Zr 4+ -O-C angles. Beyond 3.0 Å, the coordination around the Zr 4+ increases from 4 to ∼8 originating solely from the oxygen atoms of the hydroxamate groups. Our results, therefore, suggest that the competition between the hydroxamate groups versus specific water molecules in fulfilling Zr 4+ coordination sphere can have non-trivial effects in either forming unstable (DFO) or stable complexes (4HMS).