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1. Encapsulation of tricopper cluster in a synthetic cryptand enables facile redox processes from Cu ^I Cu ^I Cu ^I to Cu ^II Cu ^II Cu ^II states

   https://doi.org/10.1039/D0SC05441K  

   Zhang, Weiyao; Moore, Curtis E.; Zhang, Shiyu (March 2021, Chemical Science)

   null (Ed.)

   One-pot reaction of tris(2-aminoethyl)amine (TREN), [Cu I (MeCN) 4 ]PF 6 , and paraformaldehyde affords a mixed-valent [ TREN4 Cu II Cu I Cu I (μ 3 -OH)](PF 6 ) 3 complex. The macrocyclic azacryptand TREN4 contains four TREN motifs, three of which provide a bowl-shape binding pocket for the [Cu 3 (μ 3 -OH)] 3+ core. The fourth TREN caps on top of the tricopper cluster to form a cryptand, imposing conformational constraints and preventing solvent interaction. Contrasting the limited redox capability of synthetic tricopper complexes reported so far, [ TREN4 Cu II Cu I Cu I (μ 3 -OH)](PF 6 ) 3 exhibits several reversible single-electron redox events. The distinct electrochemical behaviors of [ TREN4 Cu II Cu I Cu I (μ 3 -OH)](PF 6 ) 3 and its solvent-exposed analog [ TREN3 Cu II Cu II Cu II (μ 3 -O)](PF 6 ) 4 suggest that isolation of tricopper core in a cryptand enables facile electron transfer, allowing potential application of synthetic tricopper complexes as redox catalysts. Indeed, the fully reduced [ TREN4 Cu I Cu I Cu I (μ 3 -OH)](PF 6 ) 2 can reduce O 2 under acidic conditions. The geometric constraints provided by the cryptand are reminiscent of Nature's multicopper oxidases (MCOs). For the first time, a synthetic tricopper cluster was isolated and fully characterized at Cu I Cu I Cu I ( 4a ), Cu II Cu I Cu I ( 4b ), and Cu II Cu II Cu I ( 4c ) states, providing structural and spectroscopic models for many intermediates in MCOs. Fast electron transfer rates (10 5 to 10 6 M −1 s −1 ) were observed for both Cu I Cu I Cu I /Cu II Cu I Cu I and Cu II Cu I Cu I /Cu II Cu II Cu I redox couples, approaching the rapid electron transfer rates of copper sites in MCO. 

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2. Metal binding and interdomain thermodynamics of mammalian metallothionein-3: enthalpically favoured Cu ⁺ supplants entropically favoured Zn ²⁺ to form Cu ₄ ⁺ clusters under physiological conditions

   https://doi.org/10.1039/d2sc00676f  

   Mehlenbacher, Matthew R.; Elsiesy, Rahma; Lakha, Rabina; Villones, Rhiza Lyne; Orman, Marina; Vizcarra, Christina L.; Meloni, Gabriele; Wilcox, Dean E.; Austin, Rachel N. (January 2022, Chemical Science)

   Metallothioneins (MTs) are a ubiquitous class of small metal-binding proteins involved in metal homeostasis and detoxification. While known for their high affinity for d 10 metal ions, there is a surprising dearth of thermodynamic data on metals binding to MTs. In this study, Zn 2+ and Cu + binding to mammalian metallothionein-3 (MT-3) were quantified at pH 7.4 by isothermal titration calorimetry (ITC). Zn 2+ binding was measured by chelation titrations of Zn 7 MT-3, while Cu + binding was measured by Zn 2+ displacement from Zn 7 MT-3 with competition from glutathione (GSH). Titrations in multiple buffers enabled a detailed analysis that yielded condition-independent values for the association constant ( K ) and the change in enthalpy (Δ H ) and entropy (Δ S ) for these metal ions binding to MT-3. Zn 2+ was also chelated from the individual α and β domains of MT-3 to quantify the thermodynamics of inter-domain interactions in metal binding. Comparative titrations of Zn 7 MT-2 with Cu + revealed that both MT isoforms have similar Cu + affinities and binding thermodynamics, indicating that Δ H and Δ S are determined primarily by the conserved Cys residues. Inductively coupled plasma mass spectrometry (ICP-MS) analysis and low temperature luminescence measurements of Cu-replete samples showed that both proteins form two Cu 4 + –thiolate clusters when Cu + displaces Zn 2+ under physiological conditions. Comparison of the Zn 2+ and Cu + binding thermodynamics reveal that enthalpically-favoured Cu + , which forms Cu 4 + –thiolate clusters, displaces the entropically-favoured Zn 2+ . These results provide a detailed thermodynamic analysis of d 10 metal binding to these thiolate-rich proteins and quantitative support for, as well as molecular insight into, the role that MT-3 plays in the neuronal chemistry of copper. 

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3. The Binding of Cu ²⁺ to Lipid Membranes Is Not Substantially Influenced by Electrostatic Screening

   https://doi.org/10.1021/jacs.4c16066  

   Reynolds, Christopher M; Fiebig, Olivia C; Marroquin, Alexa; Glaid, Andrew J; Chokhany, Kushaal; Zdenek, Ryan G; da_Cruz_Garcia, Maria Laura; Cremer, Paul S (March 2025, Journal of the American Chemical Society)
4. Mosaic Cu ^I −Cu ^II −In ^III 2D Perovskites: Pressure‐Dependence of the Intervalence Charge Transfer and a Mechanochemical Alloying Method

   https://doi.org/10.1002/anie.202300957  

   Li, Jiayi; Matheu, Roc; Ke, Feng; Liu, Zhenxian; Lin, Yu; Karunadasa, Hemamala I. (April 2023, Angewandte Chemie International Edition)

   Abstract The perovskite (BA)₄[Cu^II(Cu^IIn^III)_0.5]Cl₈(1_BA; BA⁺=butylammonium) allows us to study the high‐pressure structural, optical, and transport properties of a mixed‐valence 2D perovskite. Compressing1_BAreduces the onset energy of Cu^I/IIintervalence charge transfer from 1.2 eV at ambient pressure to 0.2 eV at 21 GPa. The electronic conductivity of1_BAincreases by 4 orders of magnitude upon compression to 20 GPa, when the activation energy for conduction decreases to 0.16 eV. In contrast, Cu^IIperovskites achieve similar conductivity at ≈50 GPa. The solution‐state synthesis of these perovskites is complicated, with more undesirable side products likely from the precursor mixtures containing three different metal ions. To circumvent this problem, we demonstrate an efficient mechanochemical synthesis to expand this family of halide perovskites with complex composition by simply pulverizing together powders of 2D Cu^IIsingle perovskites and Cu^IIn^IIIdouble perovskites. 

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5. Revealing Coexisting Cu ⁰ –Cu ⁺ Sites in Cu ₃ N Nanoensembles for Selective CC Coupling of CO ₂ Under Low Overpotential

   https://doi.org/10.1002/cssc.202500003  

   Li, Junrui; Zhong, Hong; Hong_Lee, Soo; Li, Hui; Drisdell, Walter_S; Dun, Chaochao; Burciaga, Rihana; Ingram, Conrad; Beckman, Scott_P; Urban, Jeffrey_J; et al (June 2025, ChemSusChem)

   To address a long‐existing debate on what copper species are responsible for efficient CC coupling, especially ethanol formation, in electrochemical CO₂reduction reaction, herein, a comprehensive study using Cu₃N nanocubes with a uniform size and shape, alongside a single crystalline phase is reported. The Cu₃N nanoensemble electrode has a remarkable Faradaic efficiency (FE) of 64% for ethanol production at a relatively low potential of −0.6 V versus reversible hydrogen electrode. Throughin‐operandoX‐ray absorption spectroscopy study, a dynamic phase evolution that directly correlates with changes in FE across varying applied potentials is observed. Notably, the nanoensemble with a composition of ≈71% Cu⁺and 29% Cu⁰is identified as being selective for ethanol formation at the low overpotential. Conversely, a predominantly metallic Cu phase formed at potentials more negative than −0.6 V favors the hydrogen evolution reaction. Density functional theory calculations at the Cu₃N–Cu interface substantiate that the coexistence of Cu⁰–Cu⁺not only energetically favors the ethanol reaction pathway but also destabilizes the intermediates for ethylene pathway. 

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