The speciation of metal-ligand complexes influences metal bioavailability and transport. Ni(II) is particularly interesting because it has one of the slowest rates of exchange of +2 transition metals. Capillary electrophoresis is a powerful tool for interrogating Ni(II)-ligand speciation. We developed a CE method for monitoring ligand exchange reactions: NiL+Y?NiY+L, where L and Y are aminocarboxylates. By varying aminocarboxylate structure, we explored the role of ligand rigidity, Lewis Base connectivity, and steric hindrance on rates and pathways. Our results are explained by three general reaction pathways which differ by the extent of NiL dissociation prior to Ni(II) capture. Ligand structure influenced the dominant pathway: increasing rigidity of Y or increasing the steric hindrance of L increases the extent of NiL dissociation necessary for exchange. Our results have implications for predicting metal speciation in dynamic systems and the choice of probe ligands for �kinetic speciation� of metal complexes in environmental samples.

Influence of ligand rigidity, Lewis Base connectivity, and steric hindrance on rates and pathways of nickel capture

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.