Building complexity in O2-binding copper complexes. Site-selective metalation and intermolecular O2-binding at dicopper and heterometallic complexes derived from an unsymmetric ligand.

A novel unsymmetric dinucleating ligand (L(N3N4)) combining a tridentate and a tetradentate binding sites linked through a m-xylyl spacer was synthesized as ligand scaffold for preparing homo- and dimetallic complexes, where the two metal ions are bound in two different coordination environments. Site-selective binding of different metal ions is demonstrated. L(N3N4) is able to discriminate between Cu(I) and a complementary metal (M' = Cu(I), Zn(II), Fe(II), Cu(II), or Ga(III)) so that pure heterodimetallic complexes with a general formula Cu(I)M'(L(N3N4)) are synthesized. Reaction of the dicopper(I) complex Cu(I)2(L(N3N4)) with O2 leads to the formation of two different copper-dioxygen (Cu2O2) intermolecular species (O and (T)P) between two copper atoms located in the same site from different complex molecules. Taking advantage of this feature, reaction of the heterodimetallic complexes CuM'(L(N3N4)) with O2 at low temperature is used as a tool to determine the final position of the Cu(I) center in the system because only one of the two Cu2O2 species is formed.