Copper(II) Hexaaza Macrocyclic Binuclear Complexes Obtained from the Reaction of Their Copper(I) Derivates and Molecular Dioxygen CostasMiquel RibasXavi PoaterAlbert López ValbuenaJosep Maria XifraRaül CompanyAnna DuranMiquel SolàMiquel LlobetAntoni CorbellaMontserrat UsónMiguel Angel MahíaJosé SolansXavier ShanXiaopeng Benet-BuchholzJordi 2006 Density functional theory (DFT) calculations have been carried out for a series of Cu<sup>I</sup> complexes bearing N-hexadentate macrocyclic dinucleating ligands and for their corresponding peroxo species (<b>1c</b>−<b>8c</b>) generated by their interaction with molecular O<sub>2</sub>. For complexes <b>1c</b>−<b>7c</b>, it has been found that the side-on peroxodicopper(II) is the favored structure with regard to the bis(μ-oxo)dicopper(III). For those complexes, the singlet state has also been shown to be more stable than the triplet state. In the case of <b>8c</b>, the most favored structure is the <i>trans-</i>1,2-peroxodicopper(II) because of the para substitution and the steric encumbrance produced by the methylation of the N atoms. Cu<sup>II</sup> complexes <b>4e</b>, <b>5e</b>, and <b>8e</b> have been obtained by O<sub>2</sub> oxidation of their corresponding Cu<sup>I</sup> complexes and structurally and magnetically characterized. X-ray single-crystal structures for those complexes have been solved, and they show three completely different types of Cu<sup>II</sup><sub>2</sub> structures:  (a) For <b>4e</b>, the Cu<sup>II</sup> centers are bridged by a phenolate group and an external hydroxide ligand. The phenolate group is generated from the evolution of <b>4c</b> via intramolecular arene hydroxylation. (b) For <b>5e</b>, the two Cu<sup>II</sup> centers are bridged by two hydroxide ligands. (c) For the <b>8e</b> case, the Cu<sup>II</sup> centers are ligated to terminally bound hydroxide ligands, rare because of its tendency to bridge. The evolution of complexes <b>1c</b>−<b>8c</b> toward their oxidized species has also been rationalized by DFT calculations based mainly on their structure and electrophilicity. The structural diversity of the oxidized species is also responsible for a variety of magnetic behavior:  (a) strong antiferromagnetic (AF) coupling with <i>J</i> = −482.0 cm<sup>-1</sup> (<i>g</i> = 2.30; ρ = 0.032; <i>R</i> = 5.6 × 10<sup>-3</sup>) for <b>4e</b>; (b) AF coupling with <i>J</i> = −286.3 cm<sup>-1</sup> (<i>g</i> = 2.07; ρ = 0.064; <i>R</i> = 2.6 × 10<sup>-3</sup>) for <b>5e</b>; (c) an uncoupled Cu<sup>II</sup><sub>2</sub> complex for <b>8e</b>.