title: Exceptional affinity of nanostructured organic-inorganic hybrid materials towards dioxygen: confinement effect of copper complexes.
abstract: We report the exceptional reactivity towards dioxygen of a nanostructured organic-inorganic hybrid material due to the confinement of copper cyclam within a silica matrix. The key step is the metalation reaction of the ligand, which can occur before or after xerogel formation through the sol-gel process. The incorporation of a Cu(II) center into the material after xerogel formation leads to a bridged Cu(I)/Cu(II) mixed-valence dinuclear species. This complex exhibits a very high affinity towards dioxygen, attributable to auto-organization of the active species in the solid. The remarkable properties of these copper complexes in the silica matrix demonstrate a high cooperative effect for O(2) adsorption; this is induced by close confinement of the two copper ions leading to end-on mu-eta(1):eta(1)-peroxodicopper(II) complexes. The anisotropic packing of the tetraazamacrocycle in a lamellar structure induces an exceptional reactivity of these copper complexes. We show for the first time that the organic-inorganic environment of copper complexes in a silica matrix fully model the protecting role of protein in metalloenzymes. For the first time an oxygenated dicopper(II) complex can be isolated in a stable form at room temperature, and the reduced Cu(2) (I,I) species can be regenerated after several adsorption-desorption cycles. These data also demonstrate that the coordination scheme and reactivity of the copper cyclams within the solid are quite different from that observed in solution.
authors.affiliation: LIMSAG, UMR 5633, Université de Bourgogne, UFR Sciences et Techniques, 9 avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Brandès
authors.forename: Gabriel
authors.initials: G
authors.lastname: David
authors.forename: Clément
authors.initials: C
authors.lastname: Suspène
authors.forename: Robert J P
authors.initials: RJ
authors.lastname: Corriu
authors.forename: Roger
authors.initials: R
authors.lastname: Guilard
mesh_terms: D000327:Adsorption; D016880:Anisotropy; D001665:Binding Sites; D002413:Cations, Divalent; D003300:Copper / Q000737:chemistry*; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism; D005782:Gels / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008024:Ligands; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D049329:Nanostructures / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D002413:Cations, Divalent; D004798:Enzymes; D005782:Gels; D006571:Heterocyclic Compounds; D008024:Ligands; D046912:Multiprotein Complexes; D009942:Organometallic Compounds; D010545:Peroxides; C024560:cyclam; D012822:Silicon Dioxide; D003300:Copper; D010100:Oxygen