In:
Chemical Science, Royal Society of Chemistry (RSC), Vol. 11, No. 13 ( 2020), p. 3441-3447
Abstract:
Nitrous oxide (N 2 O) contributes significantly to ozone layer depletion and is a potent greenhouse agent, motivating interest in the chemical details of biological N 2 O fixation by nitrous oxide reductase (N 2 OR) during bacterial denitrification. In this study, we report a combined experimental/computational study of a synthetic [4Cu:1S] cluster supported by N-donor ligands that can be considered the closest structural and functional mimic of the Cu Z catalytic site in N 2 OR reported to date. Quantitative N 2 measurements during synthetic N 2 O reduction were used to determine reaction stoichiometry, which in turn was used as the basis for density functional theory (DFT) modeling of hypothetical reaction intermediates. The mechanism for N 2 O reduction emerging from this computational modeling involves cooperative activation of N 2 O across a Cu/S cluster edge. Direct interaction of the μ 4 -S ligand with the N 2 O substrate during coordination and N–O bond cleavage represents an unconventional mechanistic paradigm to be considered for the chemistry of Cu Z and related metal–sulfur clusters. Consistent with hypothetical participation of the μ 4 -S unit in two-electron reduction of N 2 O, Cu K-edge and S K-edge X-ray absorption spectroscopy (XAS) reveal a high degree of participation by the μ 4 -S in redox changes, with approximately 21% S 3p contribution to the redox-active molecular orbital in the highly covalent [4Cu:1S] core, compared to approximately 14% Cu 3d contribution per copper. The XAS data included in this study represent the first spectroscopic interrogation of multiple redox levels of a [4Cu:1S] cluster and show high fidelity to the biological Cu Z site.
Type of Medium:
Online Resource
ISSN:
2041-6520
,
2041-6539
Language:
English
Publisher:
Royal Society of Chemistry (RSC)
Publication Date:
2020
detail.hit.zdb_id:
2559110-1
