Journal article

Authors list: Becker, M; Schindler, S; Karlin, KD; Kaden, TA; Kaderli, S; Palanché, T; Zuberbühler, AD

Publication year: 1999

Pages: 1989-1995

Journal: Inorganic Chemistry

Volume number: 38

Issue number: 9

ISSN: 0020-1669

DOI Link: https://doi.org/10.1021/ic981066m

Publisher: American Chemical Society

Abstract: 
We provide a mechanistic study of a monooxygenase model system and detail low-temperature stopped-flow kinetics studies in acetone as solvent, employing both the use of rapid-scanning diode-array observation and variable high-pressure (20-100 MPa) techniques. The dicopper(I) complex employed is [Cu(2)(H-XYL-H)](2+) (1), with the H-XYL-H ligand wherein a m-xylyl group links two bis[2-(2-pyridyl)ethyl]amine units. This reacts with O(2) reversibly (k(1)/k(-)(1)) giving a peroxo-dicopper(II) intermediate [Cu(2)(H-XYL-H)(O(2))](2+) (2), which thereupon irreversibly (k(2)) reacts by oxygen atom insertion (i.e., hydroxylation) of the xylyl group, producing [Cu(2)(H-XYL-O(-))(OH)](2+) (3). Activation parameters are as follows: k(1), DeltaH() = 2.1 +/- 0.7 kJ/mol, DeltaS() = -174 +/- 3 J/(K mol); k(-)(1), DeltaH() = 80.3 +/- 0.8 kJ/mol, DeltaS() = 77 +/- 3 J/(K mol); k(2), DeltaH() = 58.2 +/- 0.2 kJ/mol, DeltaS() = -5.8 +/- 0.9 J/(K mol). These values are similar to values obtained in a previous study in dichloromethane. At low temperatures and higher concentrations, the situation in acetone is complicated by a pre-equilibrium of 1 to an isomer form. The present study provides the first determination of activation volumes for individual steps in copper monooxygenase reactions. The data and analysis provide that DeltaV()(k(1)) = -15 +/- 2.5 cm(3)/mol and DeltaV()(k(-)(1)) = +4.4 +/- 0.5 cm(3)/mol for formation and dissociation of 2, respectively, while DeltaV()(k(2)) = -4.1 +/- 0.7 cm(3)/mol; a volume profile for the overall reaction has been constructed. The significance of the findings in the present study is described, and the results are compared to those for other systems.

Harvard Citation style: Becker, M., Schindler, S., Karlin, K., Kaden, T., Kaderli, S., Palanché, T., et al. (1999) Intramolecular Ligand Hydroxylation : Mechanistic High-Pressure Studies on the Reaction of a Dinuclear Copper(I) Complex with Dioxygen, Inorganic Chemistry, 38(9), pp. 1989-1995. https://doi.org/10.1021/ic981066m

APA Citation style: Becker, M., Schindler, S., Karlin, K., Kaden, T., Kaderli, S., Palanché, T., & Zuberbühler, A. (1999). Intramolecular Ligand Hydroxylation : Mechanistic High-Pressure Studies on the Reaction of a Dinuclear Copper(I) Complex with Dioxygen. Inorganic Chemistry. 38(9), 1989-1995. https://doi.org/10.1021/ic981066m