Η2-peroxo Dicopper Complex Research Articles

Synthesis, structure, and greatly improved reversible O2 binding in a structurally modulated micro-eta 2:eta 2-peroxodicopper(II) complex with room-temperature stability.

Facile O2 release from an oxyhemocyanin model has been achieved for the first time, with the new room-temperature-stable μ-η2:η2-peroxodicopper complex [Cu2O2(L2)]2+ (1). X-ray structural and spectroscopic studies on 1 show that elongation of the CuO bonds, induced by the bridgehead methyl groups of L2, is responsible for the ease of O2 release. CO/O2 binding by 1, monitored by UV/Vis spectroscopy (see picture), is completely reversible.

Theoretical Evidence of Electrophilic Superoxides in Models of Oxyhemocyanin/Oxytyrosinase Active Sites. Influence of the Ligand's Arrangement

The most widely accepted mechanism for the molecular dioxygen bioactivation by dicopper monooxidases, or their biomimetic models, in arene oxidation relies on a direct electrophilic oxygen transfer from an intermediate μ-η2:η2 peroxo dicopper complex into a substrate C−H bond. However, the electrophilic character of the activated form of dioxygen in such complexes has never been established. Extended Huckel calculations on a set of (Cu+(Im-H)3)2−O2 complexes, taken as model of oxyhemocyanin and oxytyrosinase active sites, are reported for both eclipsed and staggered arrangements of the imidazole ligands. The results obtained indicate such two conformations to be isoenergetic. In both situations, the molecular electrostatic potential maps show two striking features: (i) the plane perpendicular to the O−O bond and containing the two metal ions exhibit, as previously shown for the staggered situation, two nucleophilic potential wells; (ii) two strongly positive regions extend from the oxygens along the O−O ...