Properties of Amine-Containing Ligands That Are Necessary for Visible-Light-Promoted Catalysis with Divalent Europium.

We describe a study of the influence of amine-containing ligands on the photoredox-relevant properties of Eu II toward the rational design of Eu II -containing catalysts for visible-light-promoted photoredox reactions. We report our observations of the effects of the degree of functionalization of amines, denticity, and macrocylic ligands on the absorbance of Eu II . Ligands that contain secondary amines bathochromically shift the absorbance of EuCl 2 relative to ligands that contain primary or tertiary amines. Similarly, ligands of larger denticity have a larger bathochromic shift of the absorbance than ligands of smaller denticity. We observed that macrocyclic ligands have a larger effect on the absorbance of EuCl 2 than nonmacrocyclic ligands. Also, we report the photoredox reactivity of four new Eu II -containing complexes. These observations are potentially influential in understanding the ligand properties that promote the use of Eu II in visible-light-promoted photoredox catalysis.