Dehalogenation reaction photocatalyzed by homoleptic copper(i) complexes associated with strongly reductive sacrificial donors

Abstract

In order to perform challenging reduction reactions with light, at low cost and low toxicity, we aim at using for the first time a reductive quenching cycle with a simple, strongly colored homoleptic copper(I) complex [Cu(dipp)₂]⁺ (dipp = 2,9-diisopropyl-1,10-phenanthroline). Complexes of this family being weak photo-oxidants, we specifically designed and synthesized powerful, recyclable sacrificial electron donors D. We demonstrate that, during irradiation with LED light in the presence of D, the strong reductant [Cu(dipp)₂]⁰ is efficiently photo-generated. Further, we present the first photochemical reaction using photo-generated [Cu(dipp)₂]⁰ and evidence that the kinetics of the overall reaction are strongly affected by the oxidation potential of the sacrificial donor E(D⁺/D). Adapting the thermodynamics of sacrificial donors D and [Cu(dipp)₂]⁺ has thus allowed us to unlock a brand new concept, giving access to cheap, non-toxic solar light-generated very strong reductive power.