title: Efficient Biomimetic Hydroxylation Catalysis with a Bis(pyrazolyl)imidazolylmethane Copper Peroxide Complex.
abstract: Bis(pyrazolyl)methane ligands are excellent components of model complexes used to investigate the activity of the enzyme tyrosinase. Combining the N donors 3-tert-butylpyrazole and 1-methylimidazole results in a ligand that is capable of stabilising a (μ-η(2) :η(2) )-dicopper(II) core that resembles the active centre of tyrosinase. UV/Vis spectroscopy shows blueshifted UV bands in comparison to other known peroxo complexes, due to donor competition from different ligand substituents. This effect was investigated with the help of theoretical calculations, including DFT and natural transition orbital analysis. The peroxo complex acts as a catalyst capable of hydroxylating a variety of phenols by using oxygen. Catalytic conversion with the non-biological phenolic substrate 8-hydroxyquinoline resulted in remarkable turnover numbers. In stoichiometric reactions, substrate-binding kinetics was observed and the intrinsic hydroxylation constant, kox , was determined for five phenolates. It was found to be the fastest hydroxylation model system determined so far, reaching almost biological activity. Furthermore, Hammett analysis proved the electrophilic character of the reaction. This sheds light on the subtle role of donor strength and its influence on hydroxylation activity.
authors.affiliation: Department für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 München (Germany).|Institut für Anorganische Chemie, Rheinisch-Westfälische Technische Hochschule Aachen, Landoltweg 1, 52074 Aachen (Germany).
authors.forename: Claudia
authors.initials: C
authors.lastname: Wilfer
authors.affiliation: Institut für Anorganische Chemie, Rheinisch-Westfälische Technische Hochschule Aachen, Landoltweg 1, 52074 Aachen (Germany).
authors.forename: Patricia
authors.initials: P
authors.lastname: Liebhäuser
authors.affiliation: Institut für Anorganische Chemie, Rheinisch-Westfälische Technische Hochschule Aachen, Landoltweg 1, 52074 Aachen (Germany).
authors.forename: Alexander
authors.initials: A
authors.lastname: Hoffmann
authors.affiliation: Department für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 München (Germany).
authors.forename: Hannes
authors.initials: H
authors.lastname: Erdmann
authors.affiliation: Department für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 München (Germany).
authors.forename: Oleg
authors.initials: O
authors.lastname: Grossmann
authors.affiliation: Department für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 München (Germany).
authors.forename: Leander
authors.initials: L
authors.lastname: Runtsch
authors.affiliation: Institut für Anorganische Chemie, Rheinisch-Westfälische Technische Hochschule Aachen, Landoltweg 1, 52074 Aachen (Germany).
authors.forename: Eva
authors.initials: E
authors.lastname: Paffenholz
authors.affiliation: Department Chemie, Universität Paderborn, Warburger Straße 100, 33098 Paderborn (Germany).
authors.forename: Rahel
authors.initials: R
authors.lastname: Schepper
authors.affiliation: Department Chemie, Universität Paderborn, Warburger Straße 100, 33098 Paderborn (Germany).
authors.forename: Regina
authors.initials: R
authors.lastname: Dick
authors.affiliation: Department Chemie, Universität Paderborn, Warburger Straße 100, 33098 Paderborn (Germany).
authors.forename: Matthias
authors.initials: M
authors.lastname: Bauer
authors.affiliation: Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen (Germany).
authors.forename: Maximilian
authors.initials: M
authors.lastname: Dürr
authors.affiliation: Department Chemie und Pharmazie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen (Germany).
authors.forename: Ivana
authors.initials: I
authors.lastname: Ivanović-Burmazović
authors.affiliation: Department für Chemie und Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 München (Germany). sonja.herres-pawlis@ac.rwth-aachen.de.|Institut für Anorganische Chemie, Rheinisch-Westfälische Technische Hochschule Aachen, Landoltweg 1, 52074 Aachen (Germany). sonja.herres-pawlis@ac.rwth-aachen.de.
authors.forename: Sonja
authors.initials: S
authors.lastname: Herres-Pawlis
mesh_terms: D001686:Biological Phenomena; D032701:Biomimetics; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D006900:Hydroxylation; D007093:Imidazoles / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism; D015125:Oxyquinoline / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D011720:Pyrazoles / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D008024:Ligands; D011720:Pyrazoles; C000608155:bis(pyrazolyl)imidazolylmethane; D015125:Oxyquinoline; D003300:Copper; D014442:Monophenol Monooxygenase; C018100:1-methylimidazole
keywords: N ligands; biomimetic synthesis; copper; kinetics; structure-activity relationships