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Record Broken: A Copper Peroxide Complex with Enhanced Stability and Faster Hydroxylation Catalysis
Author(s) -
Liebhäuser Patricia,
Keisers Kristina,
Hoffmann Alexander,
Schnappinger Thomas,
Sommer Isabella,
Thoma Anne,
Wilfer Claudia,
Schoch Roland,
Stührenberg Kai,
Bauer Matthias,
Dürr Maximilian,
IvanovićBurmazović Ivana,
HerresPawlis Sonja
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201700887
Subject(s) - chemistry , substituent , catalysis , hydroxylation , reactivity (psychology) , nucleophile , steric effects , electrophile , ligand (biochemistry) , tyrosinase , medicinal chemistry , copper , electrophilic substitution , peroxide , combinatorial chemistry , stereochemistry , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology , enzyme
Tyrosinase model systems pinpoint pathways to translating Nature's synthetic abilities for useful synthetic catalysts. Mostly, they use N‐donor ligands which mimic the histidine residues coordinating the two copper centres. Copper complexes with bis(pyrazolyl)methanes with pyridinyl or imidazolyl moieties are already reported as excellent tyrosinase models. Substitution of the pyridinyl donor results in the new ligand HC(3‐ t BuPz) 2 (4‐CO 2 MePy) which stabilises a room‐temperature stable μ‐η 2 :η 2 ‐peroxide dicopper(II) species upon oxygenation. It reveals highly efficient catalytic activity as it hydroxylates 8‐hydroxyquinoline in high yields (TONs of up to 20) and much faster than all other model systems (max. conversion within 7.5 min). Stoichiometric reactions with para ‐substituted sodium phenolates show saturation kinetics which are nearly linear for electron‐rich substrates. The resulting Hammett correlation proves the electrophilic aromatic substitution mechanism. Furthermore, density functional theory (DFT) calculations elucidate the influence of the substituent at the pyridinyl donor: the carboxymethyl group adjusts the basicity and nucleophilicity without additional steric demand. This substitution opens up new pathways in reactivity tuning.