More Like this

1. Calcium‐Ion Binding Mediates the Reversible Interconversion of Cis and Trans Peroxido Dicopper Cores

   https://doi.org/10.1002/anie.202105421  

   Vargo, Natasha P.; Harland, Jill B.; Musselman, Bradley W.; Lehnert, Nicolai; Ertem, Mehmed Z.; Robinson, Jerome R. (July 2021, Angewandte Chemie International Edition)

   Abstract Coupled dinuclear copper oxygen cores (Cu₂O₂) featured in type III copper proteins (hemocyanin, tyrosinase, catechol oxidase) are vital for O₂transport and substrate oxidation in many organisms.μ‐1,2‐cisperoxido dicopper cores (^CP) have been proposed as key structures in the early stages of O₂binding in these proteins; their reversible isomerization to other Cu₂O₂cores are directly relevant to enzyme function. Despite the relevance of such species to type III copper proteins and the broader interest in the properties and reactivity of bimetallic^CPcores in biological and synthetic systems, the properties and reactivity of^CPCu₂O₂species remain largely unexplored. Herein, we report the reversible interconversion ofμ‐1,2‐transperoxido (^TP) and^CPdicopper cores. Ca^IImediates this process by reversible binding at the Cu₂O₂core, highlighting the unique capability for metal‐ion binding events to stabilize novel reactive fragments and control O₂activation in biomimetic systems. 

   more » « less
2. DFT Analysis of Methane C−H Activation and Over‐Oxidation by [Cu ₂ O] ²⁺ and [Cu ₂ O ₂ ] ²⁺ Sites in Zeolite Mordenite: Intra‐ versus Inter‐site Over‐Oxidation

   https://doi.org/10.1002/cphc.202100580  

   Panthi, Dipak; Adeyiga, Olajumoke; Odoh, Samuel_O (October 2021, ChemPhysChem)

   Abstract Methane over‐oxidation by copper‐exchanged zeolites prevents realization of high‐yield catalytic conversion. However, there has been little description of the mechanism for methane over‐oxidation at the copper active sites of these zeolites. Using density functional theory (DFT) computations, we reported that tricopper [Cu₃O₃]²⁺active sites can over‐oxidize methane. However, the role of [Cu₃O₃]²⁺sites in methane‐to‐methanol conversion remains under debate. Here, we examine methane over‐oxidation by dicopper [Cu₂O]²⁺and [Cu₂O₂]²⁺sites using DFT in zeolite mordenite (MOR). For [Cu₂O₂]²⁺, we considered the μ‐(η²:η²) peroxo‐, and bis(μ‐oxo) motifs. These sites were considered in the eight‐membered (8MR) ring of MOR. μ‐(η²:η²) peroxo sites are unstable relative to the bis(μ‐oxo) motif with a small interconversion barrier. Unlike [Cu₂O]²⁺which is active for methane C−H activation, [Cu₂O₂]²⁺has a very large methane C−H activation barrier in the 8MR. Stabilization of methanol and methyl at unreacted dicopper sites however leads to over‐oxidation via sequential hydrogen atom abstraction steps. For methanol, these are initiated by abstraction of the CH₃group, followed by OH and can proceed near 200 °C. Thus, for [Cu₂O]²⁺and [Cu₂O₂]²⁺species, over‐oxidation is an inter‐site process. We discuss the implications of these findings for methanol selectivity, especially in comparison to the intra‐site process for [Cu₃O₃]²⁺sites and the role of Brønsted acid sites. 

   more » « less
3. 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. 

   more » « less
4. Structure and magnetic characterization of some bicompartmental [N ₆ O ₂ ] divalent metal( ii ) complexes using bis(phenolato) ligands bearing two pendant bis(pyridyl) amine arms

   https://doi.org/10.1039/d3nj02380j  

   Mautner, Franz A.; Fischer, Roland C.; Torvisco, Ana; Nakashima, Kai; Handa, Makoto; Mikuriya, Masahiro; Salem, Nahed M.; Overby, Gabriel J.; Maier, Madison R.; Louka, Febee R.; et al (August 2023, New Journal of Chemistry)

   Reactions of the bicompartmental bis(phenolato) compound 6,6′-methylenebis(2-((bis(pyridin-2-ylmethyl)amino)methyl)-4-chlorophenol)hemihydrate (H 2 L ½H 2 O) with 3d metal( ii ) ions afforded novel fully structurally characterized bridged acetato dinuclear complexes [Mn 2 (HL)(μ 1,2 -OAc) 2 ]PF 6 (1) [Zn 2 (HL)(μ 1,2 -OAc)(H 2 O) 0.75 (MeOH) 0.25 ](PF 6 ) 2 ·0.45(H 2 O) (5) and [Cd 2 (HL)(μ 1,1,2 -OAc)(OAc)(H 2 O)]PF 6 ·H 2 O (6) as well as the polymeric bridged-azido tetranuclear catena -[Cu 4 (HL) 2 (μ 1,1 -N 3 ) 2 (μ 1,3 -N 3 ) 2 ](NO 3 ) 2 ·5H 2 O (4). The complex [Cu 4 (HL) 2 (ClO 4 ) 3 (H 2 O) 5 ](ClO 4 ) 3 ·5H 2 O (2) was partially characterized. In addition, three more dinuclear complexes [Cu 2 (H 2 L)(NO 3 ) 2 (H 2 O) 2 ](NO 3 ) 2 (3), [Cu 2 (HL)(OAc)(CH 3 OH)](PF 6 ) 2 (7) and [Cu 2 (HL)(NCS) 2 ]NO 3 ·2H 2 O (8) were also isolated. All complexes were characterized by CHN elemental analysis, IR and UV-Vis spectroscopy, ESI-MS, conductivity measurements and X-ray single crystal crystallography for compounds 1, 4, 5 and 6, where the bis(phenolato) ligand displayed different deprotonation (H 2 L, HL − and L 2− ). The magnetic susceptibility measurements over the temperature range 2–300 K revealed very weak antiferromagnetic coupling in dimanganese( ii ) 1 ( J = −1.64(1) cm −1 ) and almost negligible magnetic interaction in dicopper( ii ) 2 ( J = 0(3) cm −1 ). In the azido catena -[Cu 4 (HL) 2 (μ 1,1 -N 3 ) 2 (μ 1,3 -N 3 ) 2 ](NO 3 ) 2 ·5H 2 O (4) complex, the J value of −133(3) cm −1 was obtained upon moderate-to-strong antiferromagnetic coupling through the di-μ 1,3 -N 3 -bridged dicopper( ii ) unit with no magnetic interaction between the two copper( ii ) ions in the di-μ 1,1 -N 3 -bridged unit. 

   more » « less
5. Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-dithione and isoindoline-1,3-dithione ligands

   https://doi.org/10.1107/S2056989020009676  

   Wheaton, Amelia M.; Guzei, Ilia A.; Berry, John F. (August 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-dithione (SNS), isoindoline-1,3-dithione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis[(acetonitrile-κ N )(6-sulfanylidenepiperidin-2-one-κ S )copper(I)], [Cu 2 I 2 (CH 3 CN) 2 (C 5 H 7 NOS) 2 ] ( I ), bis(acetonitrile-κ N )tetra-μ 3 -iodido-bis(6-sulfanylidenepiperidin-2-one-κ S )- tetrahedro -tetracopper(I), [Cu 4 I 4 (CH 3 CN) 4 (C 5 H 7 NOS) 4 ] ( II ), catena -poly[[(μ-6-sulfanylidenepiperidin-2-one-κ 2 O : S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NOS)] n ( III ), poly[[(piperidine-2,6-dithione-κ S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NS 2 )] n ( IV ), and poly[[(μ-isoindoline-1,3-dithione-κ 2 S : S )copper(I)]-μ 3 -iodido], [CuI(C 8 H 5 NS 2 )] n ( V ). Compounds I and II crystallize as discrete dimeric and tetrameric complexes, whereas III , IV , and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexagonal [Cu 3 I 3 ] structure that is not supported by bridging ligands. Structures I , II , and IV display weak to moderately strong Cu...Cu cuprophilic interactions [Cu...Cu internuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding interactions between the N—H of the ligand and the μ 2 and μ 3 -I − atoms. Structure III contains classical N–H...O interactions between the SNO ligands that connect the molecules in a three-dimensional framework. Complex V features π–π stacking interactions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV , there were three partially occupied solvent molecules of dichloromethane and one partially occupied molecule of acetonitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015). Acta Cryst . C 71 , 9–18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent molecules. The given chemical formula and other crystal data do not take into account the solvent molecules. 

   more » « less