| Autor: |
Kirsch KE; Department of Chemistry, American University, 4400 Massachusetts Ave NW, Washington, DC, 20016, USA. stoledo@american.edu., Little ME; Department of Chemistry, St Edward's University, 3001 South Congress Ave, Austin, Texas 78704, USA., Cundari TR; Department of Chemistry, University of North Texas, 1155 Union Cir, Denton, Texas 76203, USA., El-Shaer E; Department of Chemistry, St Edward's University, 3001 South Congress Ave, Austin, Texas 78704, USA., Barone G; Department of Chemistry, St Edward's University, 3001 South Congress Ave, Austin, Texas 78704, USA., Lynch VM; Department of Chemistry, The University of Texas at Austin, 120 Inner Campus Dr Stop G2500, Austin, Texas 78712, USA., Toledo SA; Department of Chemistry, American University, 4400 Massachusetts Ave NW, Washington, DC, 20016, USA. stoledo@american.edu. |
| Abstrakt: |
A new biomimetic model complex of the active site of acireductone dioxygenase (ARD) was synthesized and crystallographically characterized ( [Ni( ii )( N -(ethyl- N 'Me 2 )(Py)(2- t -ButPhOH))(OTf)]- 1). 1 displays carbon-carbon oxidative cleavage activity in the presence of O 2 towards the substrate 2-hydroxyacetophenone. This reactivity was monitored via UV-Visible and NMR spectroscopy. We postulate that the reactivity of 1 with O 2 leads to the formation of a putative Ni(III)-superoxo transient species resulting from the direct activation of O 2 via the nickel center during the oxidative reaction. This proposed intermediate and reaction mechanism were studied in detail using DFT calculations. 1 and its substrate bound derivatives display reactivity toward mild outer sphere oxidants, suggesting ease of access to high valent Ni coordination complexes, consistent with our calculations. If confirmed, the direct activation of O 2 at a nickel center could have implications for the mechanism of action of ARD and other nickel-based dioxygenases and their respective non-traditional, enzymatic moonlighting functions, as well as contribute to a general understanding of direct oxidation of nickel(II) coordination complexes by O 2 . |
