| Abstract
| - The degree of lability of a given metal complex species is modified in the presence of a mixture of ligands.This modification is a consequence of the coupling of the association and dissociation processes of all of thecomplexes according to the competitive complexation reaction scheme. We show that, because of the mixtureeffect, the lability of a given complex usually increases when another more labile complex is added into thesystem, while it decreases upon addition of a less labile one. Typically, complexes tend to adapt to the globallability of the mixture. A quantitative evaluation of these effects for diffusion-limited conditions in a finitedomain by rigorous numerical simulation in a system with two complexes indicates that the lability degreeof a complex can change by more than 100% with respect to that in the single ligand system. The impact ofthe mixture effect on the metal flux depends at least on two main factors: the respective abundance of themetal species and the particular values of their lability degrees. Dominant complexes (i.e., those most abundantwhen these complexes have equal diffusion coefficients) undergo smaller changes in their own lability degree,but these changes have the greater impact on the overall metal flux. Partially labile complexes are moreeasily influenced by the mixture than labile or inert ones. Some mixture effects can be qualitatively predictedby an analytical expression for the lability index derived using the reaction layer approximation. For a mixtureof many complexes, the change in the lability degree of a complex due to the mixture effect can be understoodas a combination of the changes due to all of the complexes present.
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