Issue 45, 2019

Theoretical study of aromatic hydroxylation of the [Cu2(H-XYL)O2]2+ complex mediated by a side-on peroxo dicopper core and Cu-ligand effects

Abstract

In this work, the aromatic hydroxylation mechanism of the [Cu2(H-XYL)O2]2+ complex mediated by a peroxo dicopper core and Cu-ligand effects are investigated by using hybrid density functional theory (DFT) and the broken symmetry B3LYP method. Based on the calculated free-energy profiles, we proposed two available mechanisms. The first reaction steps of both mechanisms involve concerted O–O bond cleavage and C–O bond formation and the second step involves the Wagner–Meerwein rearrangement of the substrate by a [1,2] H shift (HA shift from CA to CC) or (HA shift from CA to OA) across the phenyl ring to form stable dienone intermediates, and this is followed by the protonation of bridging oxygen atoms to produce the final hydroxylated dicopper(II) product. The HA shift from CA to CC mechanism is the energetically most favorable, in which the first reaction step is the rate-limiting reaction, with a calculated free-energy barrier of 19.0 kcal mol−1 and a deuterium kinetic isotope effect of 1.0, in agreement with experimental observations. The calculation also shows that the reaction started from the P-type species of [Cu2(H-XYL)O2]2+ which is capable of mediating the direct hydroxylation of aromatic substrates without the intermediacy of an O-type species. Finally, we designed some new complexes with different Cu-ligands and found the complex that computationally possesses a higher activity in mediating the hydroxylation of the ligand based aromatic substrate; here, Cu loses a pyridyl ligand donor by dissociation, compared to the [Cu2(H-XYL)O2]2+ complex.

Graphical abstract: Theoretical study of aromatic hydroxylation of the [Cu2(H-XYL)O2]2+ complex mediated by a side-on peroxo dicopper core and Cu-ligand effects

Supplementary files

Article information

Article type
Paper
Submitted
07 Jul 2019
Accepted
30 Sep 2019
First published
01 Oct 2019

Dalton Trans., 2019,48, 16882-16893

Theoretical study of aromatic hydroxylation of the [Cu2(H-XYL)O2]2+ complex mediated by a side-on peroxo dicopper core and Cu-ligand effects

Y. F. Liu, J. Shen, S. Chen, W. Qiao, S. Zhou and K. Hong, Dalton Trans., 2019, 48, 16882 DOI: 10.1039/C9DT02814E

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