Salvador José, Garcés José Luis, Companys Encarnació, Cecilia Joan, Galceran Josep, Puy Jaume, Town Raewyn M
Departament de Química, Universitat de Lleida, Rovira Roure 191, 25198 Lleida, Spain.
J Phys Chem A. 2007 May 24;111(20):4304-11. doi: 10.1021/jp0707844. Epub 2007 May 1.
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 the complexes according to the competitive complexation reaction scheme. We show that, because of the mixture effect, the lability of a given complex usually increases when another more labile complex is added into the system, while it decreases upon addition of a less labile one. Typically, complexes tend to adapt to the global lability of the mixture. A quantitative evaluation of these effects for diffusion-limited conditions in a finite domain by rigorous numerical simulation in a system with two complexes indicates that the lability degree of a complex can change by more than 100% with respect to that in the single ligand system. The impact of the mixture effect on the metal flux depends at least on two main factors: the respective abundance of the metal species and the particular values of their lability degrees. Dominant complexes (i.e., those most abundant when 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 more easily influenced by the mixture than labile or inert ones. Some mixture effects can be qualitatively predicted by an analytical expression for the lability index derived using the reaction layer approximation. For a mixture of many complexes, the change in the lability degree of a complex due to the mixture effect can be understood as a combination of the changes due to all of the complexes present.
在配体混合物存在的情况下，给定金属络合物物种的不稳定程度会发生改变。这种改变是所有络合物根据竞争络合反应方案进行缔合和解离过程耦合的结果。我们表明，由于混合效应，当向系统中加入另一种更不稳定的络合物时，给定络合物的不稳定程度通常会增加，而加入较稳定的络合物时则会降低。通常，络合物倾向于适应混合物的整体不稳定程度。通过在具有两种络合物的系统中进行严格的数值模拟，对有限域中扩散受限条件下这些效应的定量评估表明，络合物的不稳定程度相对于单配体系统中的不稳定程度可能会变化超过100%。混合效应对金属通量的影响至少取决于两个主要因素：金属物种的各自丰度及其不稳定程度的特定值。占主导地位的络合物（即当这些络合物具有相等扩散系数时最丰富的那些络合物）自身不稳定程度的变化较小，但这些变化对整体金属通量的影响更大。部分不稳定的络合物比不稳定或惰性的络合物更容易受到混合物的影响。一些混合效应可以通过使用反应层近似法导出的不稳定指数的解析表达式进行定性预测。对于许多络合物的混合物，由于混合效应导致的络合物不稳定程度的变化可以理解为由于存在的所有络合物导致的变化的组合。
