Reversible Scavenging of Dioxygen from Air by a Copper Complex

We report that exposing the dipyrrin complex ( EMind L)Cu(N 2 ) to air affords rapid, quantitative uptake of O 2 in either solution or the solid-state to yield ( EMind L)Cu(O 2 ). The air and thermal stability of ( EMind L)Cu(O 2 ) is unparalleled in molecular copper-dioxygen coordination chemistry, attributable to the ligand flanking groups which preclude the [Cu(O 2 )] 1+ core from degradation. Despite the apparent stability of ( EMind L)Cu(O 2 ), dioxygen binding is reversible over multiple cycles with competitive solvent exchange, thermal cycling, and redox manipulations. Additionally, rapid, catalytic oxidation of 1,2-diphenylhydrazine to azoarene with the generation of hydrogen peroxide is observed, through the intermittency of an observable ( EMind L)Cu(H 2 O 2 ) adduct. The design principles gleaned from this study can provide insight for the formation of new materials capable of reversible scavenging of O 2 from air under ambient conditions with low-coordinate Cu I sorbents.