Non‐Symmetrical Sterically Challenged Phenanthroline Ligands and Their Homoleptic Copper(I) Complexes with Improved Excited‐State Properties
Léa Gimeno, Errol Blart, Jean‐Noël Rebilly, Marina Coupeau, Magali Allain, Thierry Roisnel, Alexis Quarré de Verneuil, Christophe Gourlaouen, Chantal Daniel, Yann Pellegrin
Abstract
Abstract A strategy is presented to improve the excited state reactivity of homoleptic copper–bis(diimine) complexes CuL 2 + by increasing the steric bulk around Cu I whereas preserving their stability. Substituting the phenanthroline at the 2‐position by a phenyl group allows the implementation of stabilizing intramolecular π stacking within the copper complex, whereas tethering a branched alkyl chain at the 9‐position provides enough steric bulk to rise the excited state energy E 00 . Two novel complexes are studied and compared to symmetrical models. The impact of breaking the symmetry of phenanthroline ligands on the photophysical properties of the complexes is analyzed and rationalized thanks to a combined theoretical and experimental study. The importance of fine‐tuning the steric bulk of the N–N chelate in order to stabilize the coordination sphere is demonstrated. Importantly, the excited state reactivity of the newly developed complexes is improved as demonstrated in the frame of a reductive quenching step, evidencing the relevance of our strategy.