Solution-Phase Electrochemical Characterization of Acyclic Complexes of Divalent Europium

Lanthanides have useful electronic and magnetic properties that are often tuned through coordination chemistry using a variety of ligands, such as macrocyclic ligands or ligands with conjugated π-systems. Lanthanide complexes with acyclic ligands are especially difficult to study due to their labile nature and require techniques that enable monitoring of solution dynamics. Here, we report the use of cyclic voltammetry to study the solution dynamics of a Eu^II-containing complex with the acyclic ligand, tris[2-(2-methoxyethoxy)ethyl]amine, as a model system for the study of lanthanide complexes with acyclic ligands. We describe the use of cyclic voltammetry to gain insight into coordination chemistry in solution in the presence of different counterions, correlating different coordination species in solution to specific redox peaks. Using an acyclic europium complex, we detected anions of differing coordination strength in solution using cyclic voltammetry. The ability to detect specific anions in solution could enable the use of the complex as a sensor for other anions, cations, wastewater contaminants, or metabolites. Beyond Eu, these studies represent a template to enable the study of solution dynamics of other acyclic complexes of divalent lanthanides and are widely applicable to applications in sensing, biomedical imaging, and synthesis.