Kinetic stabilities of bis-terpyridine complexes with iron(ii) and cobalt(ii) in organic solvent environments

Abstract

Though 2,2′:6′,2′′-terpyridine is commonly used as a ligand for forming metallo-supramolecular assemblies in a variety of solvent environments, little is known about how the properties of the medium influence its behavior. We have studied the kinetic stabilities of bis terpyridine complexes with iron(II) and cobalt(II), and found variations in decay rate between commonly employed solvents of more than five orders of magnitude for iron, and thirty-fold for cobalt. While numerous factors likely contribute to these effects, a clear correlation between the decay rates of the iron complexes and the solubility of terpyridine suggests that favorable solvent–ligand interactions may lower the activation barrier for dissociation by stabilizing the transition state. These results illustrate the importance of solvent selection when designing metallo-supramolecular assemblies based on terpyridine, and also provide insights for further tuning the dynamic properties of these complexes.