Mixed valence copper-sulfur clusters of highest nuclearity: a Cu8 wheel and a Cu16 nanoball

A high-nuclearity CuI/CuII nanocluster catalyst for phenol degradation

Herein, we report a 54-nuclei copper nanocluster, [Cu₅₄S₁₃O₆(^tBuS)₂₀(^tBuSO₃)₁₂] (Cu₅₄), which is the largest atom-precise Cu^I/Cu^II mix-valent cluster reported. The Cu₅₄ nanoclusters supported by TiO₂ exhibit decent photocatalytic activity for phenol degradation under visible light. This work provides a platform to explore the catalytic behaviors of Cu^I/Cu^II nanosystems.

Bis(μ-thiolato)-dicopper Containing Fully Spin Delocalized Mixed Valence Copper-Sulfur Clusters and Their Electronic Structural Properties with Relevance to the CuA Site

With aromatic and aliphatic thiol-S donor Schiff base ligands, the copper-sulfur clusters, [(L1)₈Cu^I₆Cu^II₂](ClO₄)₂·DMF·0.5CH₃OH (1) and [(L2)₁₂Cu^I₅Cu^II₁₁(μ₄-S)(μ₄-O)₆](ClO₄)·4H₂O, respectively, have been reported ( Chem. Commun. 2017, 53, 3334); HL1/HL2 are 2-(((3-methylthiophen-2-yl)methylene)amino)benzene/ethanethiol). Complex 1 comprises a wheel shaped Cu₈S₈ framework, made up of interlinked Cu₂{μ-S(R)}₂ units. To understand the properties with relevance to the Cu_A site and to check whether self-assembly generates similar type clusters to 1, three complexes, [(L3)₈Cu^I₆Cu^II₂](ClO₄)₂·(C₂H₅)₂O·2.5H₂O (2), [(L3^Cl)₈Cu^I₆Cu^II₂](ClO₄)₂·1.25(C₂H₅)₂O·1.25CH₃OH·2H₂O (3), and [(L3^CF3)₈Cu^I₆Cu^II₂](ClO₄)₂·2(C₂H₅)₂O·H₂O (4) have been synthesized with supporting ligands HL3^X (HL3 = 2-((furan-2-ylmethylene)amino)benzenethiol when X = -H; X = -Cl or -CF₃ para to thiol-S are HL3^Cl and HL3^CF3 ligands, respectively). The X-ray structures of 3 and 4 feature a similar Cu₈S₈ architecture to 1. The spectroscopic properties and the X-ray structures revealed that 2-4 are fully spin delocalized mixed valence (MV) of class-III type clusters. The structural parameters of the N₂Cu₂{μ-S(R)}₂ units of 3 and 4 closely resemble those of the MV binuclear Cu_A site. With the aid of UV-vis-NIR, EPR, and spectroelectrochemical studies, the electronic properties of these complexes have been described in comparison with the MV model complexes and Cu_A site.

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)

Model compounds have been widely utilized in understanding the structure and function of the unusual Cu₄(μ₄-S) active site (Cu_Z) of nitrous oxide reductase (N₂OR). However, only a limited number of model compounds that mimic both structural and functional features of Cu_Z are available, limiting insights about Cu_Z that can be gained from model studies. Our aim has been to construct Cu₄(μ₄-S) clusters with tailored redox activity and chemical reactivity via modulating the ligand environment. Our synthetic approach uses dicopper(I) precursor complexes (Cu₂L₂) that assemble into a Cu₄(μ₄-S)L₄ cluster with the addition of an appropriate sulfur source. Here, we summarize the features of the ligands L that stabilize precursor and Cu₄(μ₄-S) clusters, along with the alternative products that form with inappropriate ligands. The precursors are more likely to rearrange to Cu₄(μ₄-S) clusters when the Cu(I) ions are supported by bidentate ligands with 3-atom bridges, but steric and electronic features of the ligand also play crucial roles. Neutral phosphine donors have been found to stabilize Cu₄(μ₄-S) clusters in the 4Cu(I) oxidation state, while neutral nitrogen donors could not stabilize Cu₄(μ₄-S) clusters. Anionic formamidinate ligands have been found to stabilize Cu₄(μ₄-S) clusters in the 2Cu(I):2Cu(II) and 3Cu(I):1Cu(II) states, with both the formation of the dicopper(I) precursors and subsequent assembly of clusters being governed by the steric factor at the ortho positions of the N-aryl substituents. Phosphaamidinates, which combine a neutral phosphine donor and an anionic nitrogen donor in the same ligand, form multinuclear Cu(I) clusters unless the negative charge is valence-trapped on nitrogen, in which case the resulting dicopper precursor is unable to rearrange to a multinuclear cluster. Taken together, the results presented in this study provide design criteria for successful assembly of synthetic model clusters for the Cu_Z active site of N₂OR, which should enable future insights into the chemical behavior of Cu_Z.

Mercaptothiacalixarenes Steer 24 Copper(I) Centers to form a Hollow-Sphere Structure Featuring Cu2 S2 Motifs with Exceptionally Short Cu⋅⋅⋅Cu Distances

Tetramercaptotetrathiacalix[4]arene (LH₄) can be used as a coordination platform to bind four Cu^I ions at the thiolate and thioether S atoms. Donor ligands such as phosphanes can stabilize the resulting [LCu₄] units, which then remain monomeric ([(Ph₃PCu)₄L]). In the absence of donor ligands, they aggregate, providing a hexamer ([LCu₄]₆) in high yields, with a hollow‐sphere structure formed by an unprecedented Cu₂₄S₄₈ cage that is surrounded by the organic framework of the calixarene chalices. Preliminary NMR experiments with regard to the host‐guest chemistry in solution showed that the compound represents a polytopic host for acetonitrile and methane.