Calix[6]tren and copper(II): a third generation of funnel complexes on the way to redox calix-zymes.
Mono-copper enzymes play an important role in biology and their functionality is based on Cu(II)/Cu(I) redox processes. Modeling a mono-nuclear site remains a challenge for a better understanding of its intrinsic reactivity. The first member of a third generation of calixarene-based mono-copper "funnel" complexes is described. The ligand is a calix[6]arene capped by a tren unit, hence presenting a N(4) coordination site confined in a cavity. Its Cu(II) complexes were characterized by electronic and EPR spectroscopies. The x-ray structure of one of them shows a five-coordinated metal ion in a slightly distorted trigonal bipyramidal geometry thanks to its coordination to a guest ligand L (ethanol). The latter sits in the heart of the hydrophobic calixarene cone that mimics the active site chamber and the hydrophobic access channel of enzymes. Competitive binding experiments showed a preference order dimethylformamide > ethanol > MeCN for L binding at the single exchangeable metal site. Cyclic voltammetry studies showed irreversible redox processes in CH(2)Cl(2) when L is an oxygen donor caused by the redox-driven ejection of the guest at the Cu(I) level. In the presence of MeCN, a pseudoreversible process was obtained, owing to a fast equilibrium between a four and a five-coordinate Cu(I) species. Finally, a redox-driven ligand interchange of dimethylformamide for MeCN at the Cu(I) state allowed the trapping of the thermodynamically less stable Cu(II)-MeCN adduct. Hence, this work represents an important step toward the elaboration of a functional supramolecular model for redox mono-copper enzymes, named redox calix-zymes.
Izzet
Guillaume
G
Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8601, Université René Descartes, 45 Rue des Saints-Pères, 75270 Paris Cedex 06, France.
Douziech
Bénédicte
B
Prangé
Thierry
T
Tomas
Alain
A
Jabin
Ivan
I
Le Mest
Yves
Y
Reinaud
Olivia
O
D001665:Binding Sites; D001952:Bridged-Ring Compounds / Q000737:chemistry*; D047250:Calixarenes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004126:Dimethylformamide / Q000737:chemistry; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D004583:Electrons; D005029:Ethylenediamines / Q000737:chemistry*; D008024:Ligands; D046911:Macromolecular Substances / Q000737:chemistry; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010636:Phenols / Q000737:chemistry*; D011485:Protein Binding; D013053:Spectrophotometry; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction
D001952:Bridged-Ring Compounds; D005029:Ethylenediamines; D008024:Ligands; D046911:Macromolecular Substances; D010636:Phenols; C476540:calix(6)arene; C502430:calix(6)tren; D047250:Calixarenes; D003300:Copper; D004126:Dimethylformamide; D010100:Oxygen