Use of CYCLAM to probe the influence of surfaces on ligand exchange

Ligand exchange reactions greatly influence the bioavailability, fate, and transport of metal ions and pollutants in natural aqueous systems. Surfaces in these systems have been shown to influence these reactions, but the pathway by which this influence occurs is not well known. This research employs the macrocyclic ligand CYCLAM and its linear analog, which have very different interactions with surfaces, to probe the mechanism of influence. The ligand exchange reaction of Ni(II) from CYCLAM or its linear analog to CDTA was monitored using capillary zone electrophoresis and UV-vis detection. A kinetic model for the NiCYCLAM-CDTA exchange system is proposed and tested in the absence of a metal oxide surface. Further tests are needed to draw conclusions about the mechanism of surface influence on ligand exchange.