Oxidation of copper(I) hexaaza macrocyclic dinuclear complexes.

DFT calculations give insight into the formation of peroxo intermediates 1-8 from a series of Cu(I) complexes bearing N-hexadentated macrocyclic dinucleating ligands, suffering an oxidation by their interaction with molecular oxygen. The discussion is thus based on the side-on peroxo cores, omitting the case of complex 8 for which the most favored structure is the trans-peroxo due to para substitution and the steric encumbrance produced by the methylation of the aminic N atoms. The frontier molecular orbital theory explains deeply the O2 binding to the Cu(I) complexes, giving key relationships between the energy of particular orbitals of the copper complex before the O2 binding and the corresponding ones for the free O2. On the other hand, tools such as the energy decomposition analysis and Mayer bond orders reveal the slight differences due to the different types of ligands.