intermediate was also altered by the supporting ligand. Namely, oxygenation of copper(I) complex 2R at a low temperature gave a (μ-η2:η2-peroxo)dicopper(II) complex as in the case of 1Phe, but its O–O bond was relatively weakened as compared to the peroxo complex derived from 1Phe, and a small amount of a bis(μ-oxo)dicopper(III) complex co-existed. These results can be attributed to the higher electron-donor