Influence of Copper Coordination Spheres on Nitrous Oxide Reductase (N₂Or) Activity of a Mixed-Valent Copper Complex Containing a {Cu₂S} Core

Abstract

A new mixed-valent dicopper complex [5] was generated from ligand exchange by dissolving a bis(CH 3 CN) precursor [3] in acetone. Introduction of a water molecule in place of an acetonitrile ligand was evidenced by base titration and the presence of a remaining coordinated CH 3 CN by IR, 19 F NMR, and theoretical methods. The proposed structure (CH 3 CN−Cu−(SR)−Cu−OH 2 ) was successfully DFT-optimized and the calculated parameters are in agreement with the experimental data. [5] has a unique temperature-dependence EPR behavior, with a localized valence from 10 to 120 K that undergoes delocalized at room temperature. The electrochemical signatures are in the line of the other aquo parent [2] and sensibly different from the rest of the series. Similar to the case of [2], [5] was finally capable of single turnover N 2 O reduction at room temperature. N 2 was detected by GC-MS, and the redox character was confirmed by EPR and ESI-MS. Kinetic data indicate a reaction rate order close to 1 and a rate 10 times faster compared to [2]. [5] is thus the second example of that kind and highlights not only the main role of the Cu−OH 2 motif, but also that the adjacent Cu-X partner (X = OTf − in [2] and CH 3 CN in [5]) is a new actor in the casting to establish structure/activity correlations.

Synthesis and Characterization of Cu(II) and Mixed-Valence Cu(I)Cu(II) Clusters Supported by Pyridylamide Ligands

“…In addition to the extensive spectroscopic and computational studies regarding these copper proteins, the assembly and construction of bioinspired small molecular models have also been the subject of vigorous research in order to better understand the functional mechanisms of the copper proteins and use the clusters as potential catalysts. − One of the major focuses of these research studies is the mixed-valence intermediate(s) involved in the these processes. For instance, recent reports on binuclear Cu II Cu III complexes postulated the presence of such a mixed-valence species in the oxidative process of Cu/O 2 chemistry. − In the activation chemistry of small molecules such as hydrocarbons, H 2 O, NO, N 2 O, − and CO 2 , , localized and delocalized mixed-valence copper complexes have also been identified as critical intermediate species during the oxidation/reduction process.…”

Impact of Electronic and Steric Changes of Ligands on the Assembly, Stability, and Redox Activity of Cu4(μ4-S) Model Compounds of the CuZ Active Site of Nitrous Oxide Reductase (N2OR)

“…In this context, there has been great interest within the bioinorganic community in modeling this unique Cu–S assembly, leading to new aspects of the N 2 O activation and reduction being discovered. − A diverse class of complexes − resulted from the attempts in synthesizing structural and/or functional model complexes of Cu Z , including notable work by the Tolman, , Murray, Torelli, , and Hilhouse , groups. While these compounds partially modeled aspects of Cu Z and brought new insights into Cu–S coordination chemistry and N 2 O activation, there are only a handful of compounds that structurally model the unique Cu 4 (μ 4 -S) core of Cu Z , ,− only two of which are reactive toward N 2 O. , The lack of tunable and predictable synthetic protocols giving control over Cu–S complexation hinders the application of synthetic model studies for mechanistic investigation of Cu Z .…”

Construction of eight mixed-valence pentanuclear CuI4CuII clusters using ligands with inhomogeneous electron density distribution: synthesis, characterization and photothermal properties

“…Mixed-valence polynuclear metal clusters with various structures and unique optical properties are significant for a variety of potential applications. [15][16][17][18] Owing to their distinctive intervalence charge transfer (IVCT) process, those compounds show unique optical absorption and are distinctly different from those single valence compounds. 19,20 Typically, mixedvalence W V /W VI tungsten oxides act as a deep-blue powder, which is quite distinct from the colorless single valence tungsten oxides.…”