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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. Crystal structures of three copper(II)–2,2′-bipyridine (bpy) compounds, [Cu(bpy) 2 (H 2 O)][SiF 6 ]·4H 2 O, [Cu(bpy) 2 (TaF 6 ) 2 ] and [Cu(bpy) 3 ][TaF 6 ] 2 and a related coordination polymer, [Cu(bpy)(H 2 O) 2 SnF 6 ] n

   https://doi.org/10.1107/S2056989021000633  

   Nisbet, Matthew L. ; Hiralal, Emily ; Poeppelmeier, Kenneth R. ( February 2021 , Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   We report the hydrothermal syntheses and crystal structures of aquabis(2,2′-bipyridine-κ 2 N , N ′)copper(II) hexafluoridosilicate tetrahydrate, [Cu(bpy) 2 (H 2 O)][SiF 6 ]·4H 2 O (bpy is 2,2′-bipyridine, C 10 H 8 N 2 ), (I), bis(2,2′-bipyridine-3κ 2 N , N ′)-di-μ-fluorido-1:3κ 2 F : F ;2:3κ 2 F : F -decafluorido-1κ 5 F ,2κ 5 F -ditantalum(V)copper(II), [Cu(bpy) 2 (TaF 6 ) 2 ], (II), tris(2,2′-bipyridine-κ 2 N , N ′)copper(II) bis[hexafluoridotantalate(V)], [Cu(bpy) 3 ][TaF 6 ] 2 , (III), and catena -poly[[diaqua(2,2′-bipyridine-κ 2 N , N ′)copper(II)]-μ-fluorido-tetrafluoridotin-μ-fluorido], [Cu(bpy)(H 2 O) 2 SnF 6 ] n , (IV). Compounds (I), (II) and (III) contain locally chiral copper coordination complexes with C 2 , D 2 , and D 3 symmetry, respectively. The extended structures of (I) and (IV) are consolidated by O—H...F and O—H...O hydrogen bonds. The structure of (III) was found to be a merohedral (racemic) twin. 

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3. Binuclear Cu A Formation in Biosynthetic Models of Cu A in Azurin Proceeds via a Novel Cu(Cys) 2 His Mononuclear Copper Intermediate

   https://doi.org/10.1021/acs.biochem.5b00659  

   Chakraborty, Saumen ; Polen, Michael J. ; Chacón, Kelly N. ; Wilson, Tiffany D. ; Yu, Yang ; Reed, Julian ; Nilges, Mark J. ; Blackburn, Ninian J. ; Lu, Yi ( October 2015 , Biochemistry)
4. Metastability and Photoelectrochemical Properties of Cu 2 SnO 3 and Cu 2–x Li x TiO 3 : Two Cu(I)-Based Oxides with Delafossite Structures

   https://doi.org/10.1021/acs.chemmater.2c03563  

   O’Donnell, Shaun ; Kremer, Reinhard K. ; Maggard, Paul A. ( February 2023 , Chemistry of Materials)
5. Synthesis and Characterization of Cu(II) and Mixed-Valence Cu(I)Cu(II) Clusters Supported by Pyridylamide Ligands

   https://doi.org/10.1021/acs.inorgchem.0c00008  

   Schneider, Joseph D. ; Smith, Brett A. ; Williams, Grant A. ; Powell, Douglas R. ; Perez, Felio ; Rowe, Gerard T. ; Yang, Lei ( April 2020 , Inorganic Chemistry)