Upon the addition of cations, the observed electrochemical behavior of crown ether compounds containing or bearing reducible functions sometimes exhibits two waves or sometimes a single wave that is shifted in position relative to the original redox couple. The type of electrochemical behavior observed depends upon the binding (stability) constant (KS) for the neutral ligand-cation interaction and the binding constant (KSE) for the reduced ligand-cation interaction. A computer-based, digital simulation scheme has been devised that leads one to the conclusion that two distinct waves will be observed only when the initial cation binding constant is large and that a shifted wave will result from weaker cation-macrocycle interactions. Of special significance is the fact that the cation binding enhancement (KSE/KS) calculated from the E° values measured from the two distinct waves will generally be in error for cases in which KS for the neutral ligand-cation interaction falls in the range 1-104. For ligands in this binding range, the digital simulation procedures reported here appear to be particularly useful for the analysis of the voltammetric data.
ASJC Scopus subject areas
- Analytical Chemistry