Homoleptic copper(II) and copper(I) complexes of 5,6-dihydro-5,6-epoxy-1,10-phenanthroline. Six-coordinate copper(I) in solution

► [CuL3]2+ where L is 5,6-dihydro-5,6-epoxy-1,10-phenanthroline characterized structurally. ► Its Cu(II/I) potential is 0.32 V vs NHE. ► [CuL2]+ has a Cu(II/I) potential of 0.68 V vs NHE. ► [CuL2]+ can bind another L to yield a six coordinate Cu(I) species in solution. ► NMR titration.