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Supramolecular Assembly with Calix[6]arene and Copper Ions − Formation of a Novel Tetranuclear Core Exhibiting Unusual Redox Properties and Catecholase Activity
Author(s) -
Sénèque Olivier,
Campion Morgan,
Douziech Bénédicte,
Giorgi Michel,
Rivière Eric,
Journaux Yves,
Mest Yves Le,
Reinaud Olivia
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200208)2002:8<2007::aid-ejic2007>3.0.co;2-z
Subject(s) - chemistry , calixarene , supramolecular chemistry , acetonitrile , electron paramagnetic resonance , redox , bioinorganic chemistry , copper , crystallography , stereochemistry , imidazole , polymer chemistry , photochemistry , inorganic chemistry , molecule , crystal structure , organic chemistry , physics , nuclear magnetic resonance
The supramolecular biomimetic chemistry based on calix[6]arene N‐ligands has been further explored. A tris(imidazole)Cu I complex was treated with 1 mol‐equiv. of cuprous ion under dioxygen to produce a tetranuclear cupric species. X‐ray structural determination of this novel Cu 4 complex revealed that the self‐inclusion of an imidazolyl coordinating arm into the hydrophobic calixarene cavity provides the base of coordination for a {ClImCu(OH) 2 CuIm 2 } 2 assembly. The Cu 4 core is maintained in solution and is stable even in a coordinating solvent such as acetonitrile. Magnetic susceptibility measurements evidenced a strong antiferromagnetic coupling in each Cu(OH) 2 Cu subunit with J = −408 cm −1 . The complex displayed catecholase activity in the presence of 3,5‐di‐ tert ‐butylcatechol behaving as a four‐electron hole with, however, a sluggish Cu I 4 ⇄ Cu II 4 regeneration through O 2 autooxidation. Finally, electrochemical studies revealed two oxidative reversible processes that successively gave rise to a {Cu II Cu III }{Cu II 2 } and a {Cu II Cu III } 2 mixed‐valence species that could be characterized by UV/Vis and EPR spectroscopy. The overall structure and behavior of this tetranuclear complex is reminiscent of multicopper enzymes. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)