Quantitation of Cu+‐catalyzed Decomposition of S‐Nitrosoglutathione Using Saville and Electrochemical Detection: a Pronounced Effect of Glutathione and Copper Concentrations

S‐nitrosothiols (RSNOs) are composed of nitric oxide (NO) bound to the sulfhydryl group of amino acids of peptides or proteins. There is a great interest for their quantitation in biological fluids as they have a crucial impact on physiological and pathophysiological events. Most analytical methodologies for quantitation of RSNOs are based on their decomposition followed by the detection of the released NO. In order to obtain the optimal sensitivity for each detection method, the total decomposition of RSNOs is highly desired. The decomposition of RSNOs can be obtained by using catalytically active metal ions, such as Cu⁺, obtained from CuSO₄ in presence of a reducing agent such as glutathione (GSH) that is naturally present in biological environment. In this work, we have re‐investigated the decomposition of S‐nitrosoglutathione (GSNO) which is the most abundant in vivo low molecular weight RSNO, with a special emphasis on the effect of CuSO₄, GSH, and GSNO concentrations and of their ratio. To this aim, GSNO decomposition optimization was performed by both indirect (Griess assay) and direct (real time electrochemical detection of NO at NO‐microsensor) quantitation methods. Our results show that the ratio between CuSO₄, GSH and GSNO should be adjusted to tune the highest decomposition rate of GSNO and the most efficient electrochemical detection of released NO; also it shows the deleterious effect of very high GSH concentration on the detection of GSNO.     

Cobalt Phthalocyanine Molecular Electrode for the Electrochemical Investigation of the Release of Glutathione upon Copper‐Catalyzed Decomposition of S‐Nitrosoglutathione

Decomposition of S‐nitrosoglutathione (GSNO) in phosphate buffer solution at physiological pH 7.4 in the presence of cuprous ion as a catalyst and sodium borohydride as a reducing agent is analyzed by observing the transient apparition of reduced glutathione GSH through its electrooxidation. Transient formation of GSH, upon decomposition of 1 mM GSNO in presence of 0.025 mM Cu(NO₃)₂ and 1 mM NaBH₄ was detected by using an ordinary pyrolytic graphite electrode modified with an adsorbed monolayer of cobalt phthalocyanine at 0 V vs. SCE.     

S‐Nitrosoglutathione‐Based Nitric Oxide‐Releasing Nanofibers Exhibit Dual Antimicrobial and Antithrombotic Activity for Biomedical Applications

The novel use of nanofibers as a physical barrier between blood and medical devices has allowed for modifiable, innovative surface coatings on devices ordinarily plagued by thrombosis, delayed healing, and chronic infection. In this study, the nitric oxide (NO) donor S‐nitrosoglutathione (GSNO) is blended with the biodegradable polymers polyhydroxybutyrate (PHB) and polylactic acid (PLA) for the fabrication of hemocompatible, antibacterial nanofibers tailored for blood‐contacting applications. Stress/strain behavior of different concentrations of PHB and PLA is recorded to optimize the mechanical properties of the nanofibers. Nanofibers incorporated with different concentrations of GSNO (10, 15, 20 wt%) are evaluated based on their NO‐releasing kinetics. PLA/PHB + 20 wt% GSNO nanofibers display the greatest NO release over 72 h (0.4–1.5 × 10^?10 mol mg^?1 min^?1). NO‐releasing fibers successfully reduce viable adhered bacterial counts by ≈80% after 24 h of exposure to Staphylococcus aureus. NO‐releasing nanofibers exposed to porcine plasma reduce platelet adhesion by 64.6% compared to control nanofibers. The nanofibers are found noncytotoxic (>95% viability) toward NIH/3T3 mouse fibroblasts, and 4′,6‐diamidino‐2‐phenylindole and phalloidin staining shows that fibroblasts cultured on NO‐releasing fibers have improved cellular adhesion and functionality. Therefore, these novel NO‐releasing nanofibers provide a safe antimicrobial and hemocompatible coating for blood‐contacting medical devices.     

A novel two‐dimensional CuSCN network templated by 2,2′‐dimethyl‐1,1′‐(butane‐1,4‐diyl)bis(1H‐imidazol‐3‐ium) cations

The cation‐templated self‐assembly of 1,4‐bis(2‐methyl‐1H‐imidazol‐1‐yl)butane (bmimb) with CuSCN gives rise to a novel two‐dimensional network, namely catena‐poly[2,2′‐dimethyl‐1,1′‐(butane‐1,4‐diyl)bis(1H‐imidazol‐3‐ium) [tetra‐μ₂‐thiocyanato‐κ⁴S:S;κ⁴S:N‐dicopper(I)]], {(C₁₂H₂₀N₄)[Cu₂(NCS)₄]}_n. The Cu^I cation is four‐coordinated by one N and three S atoms, giving a tetrahedral geometry. One of the two crystallographically independent SCN⁻ anions acts as a μ₂‐S:S bridge, binding a pair of Cu^I cations into a centrosymmetric [Cu₂(NCS)₂] subunit, which is further extended into a two‐dimensional 4⁴‐sql net by another kind of SCN⁻ anion with an end‐to‐end μ₂‐S:N coordination mode. Interestingly, each H₂bmimb dication, lying on an inversion centre, threads through one of the windows of the two‐dimensional 4⁴‐sql net, giving a pseudorotaxane‐like structure. The two‐dimensional 4⁴‐sql networks are packed into the resultant three‐dimensional supramolecular framework through bmimb–SCN N—H...N hydrogen bonds.     

Formation of the Distinct Redox‐Interrelated Forms of Nitric Oxide from Reaction of Dinitrosyl Iron Complexes (DNICs) and Substitution Ligands

Release of the distinct NO redox‐interrelated forms (NO⁺, ^.NO, and HNO/NO^?), derived from reaction of the dinitrosyl iron complex (DNIC) [(NO)₂Fe(C₁₂H₈N)₂]^? ( 1 ) (C₁₂H₈N=carbazolate) and the substitution ligands (S₂CNMe₂)₂, [SC₆H₄‐o‐NHC(O)(C₅H₄N)]₂ ((PyPepS)₂), and P(C₆H₃‐3‐SiMe₃‐2‐SH)₃ ([P(SH)₃]), respectively, was demonstrated. In contrast to the reaction of (PyPepS)₂ and DNIC 1 in a 1:1 stoichiometry that induces the release of an NO radical and the formation of complex [PPN][Fe(PyPepS)₂] ( 4 ), the incoming substitution ligand (S₂CNMe₂)₂ triggered the transformation of DNIC 1 into complex [(NO)Fe(S₂CNMe₂)₂] ( 2 ) along with N‐nitrosocarbazole ( 3 ). The subsequent nitrosation of N‐acetylpenicillamine (NAP) by N‐nitrosocarbazole ( 3 ) to produce S‐nitroso‐N‐acetylpenicillamine (SNAP) may signify the possible formation pathway of S‐nitrosothiols from DNICs by means of transnitrosation of N‐nitrosamines. Protonation of DNIC 1 by [P(SH)₃] triggers the release of HNO and the generation of complex [PPN][Fe(NO)P(C₆H₃‐3‐SiMe₃‐2‐S)₃] ( 5 ). In a similar fashion, the nucleophilic attack of the chelating ligand P(C₆H₃‐3‐SiMe₃‐2‐SNa)₃ ([P(SNa)₃]) on DNIC 1 resulted in the direct release of [NO]^? captured by [(¹⁵NO)Fe(SPh)₃]^?, thus leading to [(¹⁵NO)(¹⁴NO)Fe(SPh)₂]^?. These results illustrate one aspect of how the incoming substitution ligands ((S₂CNMe₂)₂ vs. (PyPepS)₂ vs. [P(SH)₃]/[P(SNa)₃]) in cooperation with the carbazolate‐coordinated ligands of DNIC 1 function to control the release of NO⁺, ^.NO, or [NO]^? from DNIC 1 upon reaction of complex 1 and the substitution ligands. Also, these results signify that DNICs may act as an intermediary of NO in the redox signaling processes by providing the distinct redox‐interrelated forms of NO to interact with different NO‐responsive targets in biological systems.     

Ratiometric two-photon excited photoluminescence of quantum dots triggered by near-infrared-light for real-time detection of nitric oxide release in situ

Probe-donor integrated nanocomposites were developed from conjugating silica-coated Mn²⁺:ZnS quantum dots (QDs) with MoS₂ QDs and photosensitive nitric oxide (NO) donors (Fe₄S₃(NO)₇⁻, RBS). Under excitation with near-infrared (NIR) light at 808 nm, the Mn²⁺:ZnS@SiO₂/MoS₂-RBS nanocomposites showed the dual-emissive two-photon excited photoluminescence (TPEPL) that induced RBS photolysis to release NO in situ. NO caused TPEPL quenching of Mn²⁺:ZnS QDs, but it produced almost no impact on the TPEPL of MoS₂ QDs. Hence, the nanocomposites were developed as a novel QDs-based ratiometric TPEPL probe for real-time detection of NO release in situ. The ratiometric TPEPL intensity is nearly linear (R² = 0.9901) with NO concentration in the range of 0.01∼0.8 μM, which corresponds to the range of NO release time (0∼15 min). The detection limit was calculated to be approximately 4 nM of NO. Experimental results confirmed that this novel ratiometric TPEPL probe possessed high selectivity and sensitivity for the detection of NO against potential competitors, and especially showed high detection performance for NIR-light triggered NO release in tumor intracellular microenvironments. These results would promote the development of versatile probe-donor integrated systems, also providing a facile and efficient strategy to real-time detect the highly controllable drug release in situ, especially in physiological microenvironments.     

Cu1,45Er0,85S2: Ein Kupfer(I)‐Erbium(III)‐Sulfid mit kationendefekter CaAl2Si2‐Struktur

Cu_1.45Er_0.85S₂: A Copper(I) Erbium(III) Sulfide with Cation‐Deficient CaAl₂Si₂‐Type Structure Attempts to synthesize single‐phase CuYS₂‐type copper(I) erbium(III) disulfide (CuErS₂) from 1 : 1 : 2‐molar mixtures of the elements (Cu, Er and S) after seven days at 900 °C in sealed evacuated silica tubes failed with equimolar amounts of CsCl working as flux and reagent. In these cases, quaternary CsCu₃Er₂S₅ (orthorhombic, Cmcm; a = 394.82(4), b = 1410.9(1), c = 1667.2(2) pm, Z = 4) and ternary Cu_1.45Er_0.85S₂ (trigonal, P3m1; a = 389.51(4), c = 627.14(6) pm, Z = 1) become the unexpected by‐products. Both emerge even as yellow single crystals (lath‐shaped fibres and platelets, respectively, with triangular cross‐section) and both crystal structures contain condensed [CuS₄] and [ErS₆] units as dominating building blocks. The ternary sulfide Cu_1.45Er_0.85S₂ exhibits CdI₂‐analogous layers {[(Er³⁺)(S^2–)_6/3]^–} of edge‐shared [ErS₆] octahedra (d(Er–S) = 272 pm, 6 × ) which are piled up parallel (001) and interconnected by interstitial Cu⁺ cations in tetrahedral S^2– coordination (d(Cu–S) = 236 pm, 1 × ; 240 pm, 3 × ). The latter thereby form anionic layers {([(Cu⁺)(S^2–)_4/4]^–)₂} as well, consisting of [CuS₄] tetrahedra which share three cis‐oriented edges. When the S^2– anions arrange hexagonally closest‐packed and the corresponding layers are symbolized with capital Roman letters, the Er³⁺ cations (small Roman) and the Cu⁺ cations (small Greek letters) reside layerwise alternatingly within half of the octahedral (Er³⁺) and tetrahedral (Cu⁺) voids according to … AcB αβ AcB αβ A … . Since both kinds of cations occupy only a certain percentage (Cu⁺: 72.6%, Er³⁺: 85.1%) of their regular positions, the crystal structure of Cu_1.45Er_0.85S₂ can be addressed as a double cation‐deficient CaAl₂Si₂‐type arrangement according to (Er_0.85□_0.15)(Cu_1.45□_0.55)S₂. The partial occupation could be established by both released site occupation factors in the course of the crystal structure refinement and electron beam X‐ray microanalysis (EDX).     

The Copper(II)‐Catalyzed Oxidation of Glutathione

The kinetics and mechanisms of the copper(II)‐catalyzed GSH (glutathione) oxidation are examined in the light of its biological importance and in the use of blood and/or saliva samples for GSH monitoring. The rates of the free thiol consumption were measured spectrophotometrically by reaction with DTNB (5,5′‐dithiobis‐(2‐nitrobenzoic acid)), showing that GSH is not auto‐oxidized by oxygen in the absence of a catalyst. In the presence of Cu²⁺, reactions with two timescales were observed. The first step (short timescale) involves the fast formation of a copper–glutathione complex by the cysteine thiol. The second step (longer timescale) is the overall oxidation of GSH to GSSG (glutathione disulfide) catalyzed by copper(II). When the initial concentrations of GSH are at least threefold in excess of Cu²⁺, the rate law is deduced to be ?d[thiol]/dt=k[copper–glutathione complex][O₂]^0.5[H₂O₂]^?0.5. The 0.5^th reaction order with respect to O₂ reveals a pre‐equilibrium prior to the rate‐determining step of the GSSG formation. In contrast to [Cu²⁺] and [O₂], the rate of the reactions decreases with increasing concentrations of GSH. This inverse relationship is proposed to be a result of the competing formation of an inactive form of the copper–glutathione complex (binding to glutamic and/or glycine moieties).     

An All‐Alkynyl Protected 74‐Nuclei Silver(I)–Copper(I)‐Oxo Nanocluster: Oxo‐Induced Hierarchical Bimetal Aggregation and Anisotropic Surface Ligand Orientation

The hardness of oxo ions (O^2?) means that coinage‐metal (Cu, Ag, Au) clusters supported by oxo ions (O^2?) are rare. Herein, a novel μ₄‐oxo supported all‐alkynyl‐protected silver(I)–copper(I) nanocluster [Ag_74?xCu_xO₁₂(PhC≡C)₅₀] ( NC‐1 , avg. x=37.9) is characterized. NC‐1 is the highest nuclearity silver–copper heterometallic cluster and contains an unprecedented twelve interstitial μ₄‐oxo ions. The oxo ions originate from the reduction of nitrate ions by NaBH₄. The oxo ions induce the hierarchical aggregation of Cu^I and Ag^I ions in the cluster, forming the unique regioselective distribution of two different metal ions. The anisotropic ligand coverage on the surface is caused by the jigsaw‐puzzle‐like cluster packing incorporating rare intermolecular C?H???metal agostic interactions and solvent molecules. This work not only reveals a new category of high‐nuclearity coinage‐metal clusters but shows the special clustering effect of oxo ions in the assembly of coinage‐metal clusters.     

Mononitrosyl‐ und trans‐Dinitrosyl‐Komplexe von Phthalocyaninaten des Mangans und Rheniums

Mononitrosyl and trans ‐Dinitrosyl Complexes of Phthalocyaninates of Manganese and Rhenium Tetra(n‐butyl)ammonium or di(triphenylphosphane)iminium nitrosylacidophthalocyaninato(2–)manganate, (cat)[Mn(NO)(X)pc^2–] (X = ONO, NCO, N₃; cat = ⁿBu₄N, PNP) is prepared from acidophthalocyaninato(2–)manganese, [Mn(X)pc^2–], (cat)NO₂ and (ⁿBu₄N)BH₄ in CH₂Cl₂ or from nitrosylphthalocyaninato(2–)manganese, [Mn(NO)pc^2–] and (ⁿBu₄N)X (X = ONO, NCO, N₃, NCS) at T < 120 °C, respectively. [Mn(NO)(X)pc^2–]^– dissociates in methanol, and [Mn(NO)pc^2–] precipitates. Nitrito(O)phthalocyaninato(2–)manganese, (cat)NO₂ and hydrogensulfide yield trans‐di(nitrosyl)phthalocyaninato(2–)manganate, ^trans[Mn(NO)₂pc^2–]^–, isolated as red violet (PNP) and (ⁿBu₄N) complex salt. Nitrosyl(triphenylphosphane oxide)phthalocyaninato(2–)manganese, [Mn(NO)(OPPh₃)pc^2–] is obtained by addition of OPPh₃ to [Mn(NO)pc^2–] at 200 °C. Di(triphenylphosphane)phthalocyaninato(2–)rhenium(II) and (PNP)NO₂ in CH₂Cl₂ or in molten (PNP)NO₂ and PPh₃ at 100 °C yields green blue l‐di(triphenylphosphane)iminium nitrosylnitrito(O)phthalocyaninato(2–)rhenate, ^l(PNP)[Re(NO)(ONO)pc^2–]. Similarly, but with (ⁿBu₄N)NO₂ red plates of tetra‐(n‐butyl)ammonium trans‐di(nitrosyl)phthalocyaninato(2–)rhenate, (ⁿBu₄N)^trans[Re(NO)₂pc^2–] is isolated. Addition of (PNP)Br or (PNP)PF₆ to a concentrated solution of (ⁿBu₄N)^trans[Re(NO)₂pc^2–] in pyridine precipitates ^l(PNP)^trans[Re(NO)₂pc^2–]. (ⁿBu₄N)^trans[Re(NO)₂pc^2–] and PPh₃ at 300 °C yield blue green nitrosyl(triphenylphosphane oxide)phthalocyaninato(2–)‐ rhenium, [Re(NO)(OPPh₃)pc^2–], that is oxidised with iodine precipitating nitrosyl(triphenylphosphane oxide)phthalocyaninato(2–)rhenium triiodide, [Re(NO)(OPPh₃)pc^2–]I₃. The crystal structures of ^l(PNP)[Mn(NO)(ONO)pc^2–] ( 1 ), ^l(PNP)‐ [Mn(NO)(NCO)pc^2–] ( 2 ), ^l(PNP)^trans[Mn(NO)₂pc^2–] ( 3 ), ^l(PNP)^trans[Re(NO)₂pc^2–] ( 4 ) [Mn(NO)(OPPh₃)pc^2–] ( 5 ), [Re(NO)(OPPh₃)pc^2–] ( 6 ), and [Re(NO)(OPPh₃)pc^2–]I₃ · CH₂Cl₂ ( 7 ) have been determined. The M–N(NO) distance varies between 1.623(12) Å in 5 and 1.846(3) Å in 3 . The M–N–O moiety is almost linear. The UV‐Vis spectra with the B band at ca. 14500 cm^–1and the Q band at 30400 cm^–1 do not dependent significantly on the axial ligand and the metal atom and its oxidation state. N–O stretching vibrations are observed in the IR spectra between 1701 cm^–1 in 3 and 1753 cm^–1 in [Mn(NO)pc^2–] or for the Re series between 1571 cm^–1 in 4 and 1724 cm^–1 in 7 . M–N(NO) stretching and M–N–O deformation vibrations are assigned in the IR spectra and resonance Raman spectra between 486 cm^–1 in 4 and 620 cm^–1 in 1 .     

EPR Spectroscopy of 4, 4′‐Bis(tert‐butyl)‐2, 2′‐bipyridine‐1, 2‐dithiolatocuprates(II) in Host Lattices with Different Coordination Geometries

A series of new heteroleptic MN₂S₂ transition metal complexes with M = Cu²⁺ for EPR measurements and as diamagnetic hosts Ni²⁺, Zn²⁺, and Pd²⁺ were synthesized and characterized. The ligands are N₂ = 4, 4′‐bis(tert‐butyl)‐2, 2′‐bipyridine (tBu₂bpy) and S₂ =1, 2‐dithiooxalate, (dto), 1, 2‐dithiosquarate, (dtsq), maleonitrile‐1, 2‐dithiolate, or 1, 2‐dicyanoethene‐1, 2‐dithiolate, (mnt). The Cu^II complexes were studied by EPR in solution and as powders, diamagnetically diluted in the isostructural planar [Ni^II(tBu₂bpy)(S₂)] or[Pd^II(tBu₂bpy)(S₂)] as well as in tetrahedrally coordinated[Zn^II(tBu₂bpy)(S₂)] host structures to put steric stress on the coordination geometry of the central CuN₂S₂ unit. The spin density contributions for different geometries calculated from experimental parameters are compared with the electronic situation in the frontier orbital, namely in the semi‐occupied molecular orbital (SOMO) of the copper complex, derived from quantum chemical calculations on different levels (EHT and DFT). One of the hosts, [Ni^II(tBu₂bpy)(mnt)], is characterized by X‐ray structure analysis to prove the coordination geometry. The complex crystallizes in a square‐planar coordination mode in the monoclinic space group P2₁/a with Z = 4 and the unit cell parameters a = 10.4508(10) Å, b = 18.266(2) Å, c = 12.6566(12) Å, β = 112.095(7)°. Oxidation and reductions potentials of one of the host complexes, [Ni(tBu₂bpy)(mnt)], were obtained by cyclovoltammetric measurements.     

Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu‐SSZ‐13

Operando X‐ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu‐exchanged SSZ‐13. Catalysts prepared to contain only isolated, exchanged Cu^II ions evidence both Cu^II and Cu^I ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH₃ together are necessary for Cu^II reduction to Cu^I. DFT calculations show that NO‐assisted NH₃ dissociation is both energetically favorable and accounts for the observed Cu^II reduction. The calculations predict in situ generation of Brønsted sites proximal to Cu^I upon reduction, which we quantify in separate titration experiments. Both NO and O₂ are necessary for oxidation of Cu^I to Cu^II, which DFT suggests to occur by a NO₂ intermediate. Reaction of Cu‐bound NO₂ with proximal NH₄⁺ completes the catalytic cycle. N₂ is produced in both reduction and oxidation half‐cycles.     

The conformations of two copper(I) complexes of 1H‐benzimidazole‐2(3H)‐thione and thiosaccharinate

(Acetonitrile‐1κN)[μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S][1H‐benzimidazole‐2(3H)‐thione‐2κS]bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₂(CH₃CN)] or [Cu₂(tsac)₂(Sbim)₂(CH₃CN)] [tsac is thiosaccharinate and Sbim is 1H‐benzimidazole‐2(3H)‐thione], (I), is a new copper(I) compound that consists of a triply bridged dinuclear Cu—Cu unit. In the complex molecule, two tsac anions and one neutral Sbim ligand bind the metals. One anion bridges via the endocyclic N and exocyclic S atoms (μ‐S:N). The other anion and one of the mercaptobenzimidazole molecules bridge the metals through their exocyclic S atoms (μ‐S:S). The second Sbim ligand coordinates in a monodentate fashion (κS) to one Cu atom, while an acetonitrile molecule coordinates to the other Cu atom. The Cu^I—Cu^I distance [2.6286 (6) Å] can be considered a strong `cuprophilic' interaction. In the case of [μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S]bis[1H‐benzimidazole‐2(3H)‐thione]‐1κS;2κS‐bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₃] or [Cu₂(tsac)₂(Sbim)₃], (II), the acetonitrile molecule is substituted by an additional Sbim ligand, which binds one Cu atom via the exocylic S atom. In this case, the Cu^I—Cu^I distance is 2.6068 (11) Å.     

Magnetically recyclable nano copper/chitosan in O‐arylation of phenols with aryl halides

Interaction of chitosan (CS) with Fe₃O₄, followed by embedding Cu nanoparticles (NPs) on the magnetic surface through adsorption of Cu²⁺, and its reduction to Cu^o via NaBH₄, offers a reusable efficient catalyst (Fe₃O₄/CS‐Cu NPs) that is employed in cross‐coupling reactions of aryl halides with phenols, which affords the corresponding diaryl ethers, with good to excellent yields. The catalyst is completely recoverable from the reaction mixture by using an external magnet. It can be reused four times, without significant loss in its catalytic activity.     

Electrocatalysis of Nitrate Reduction at Copper‐Nickel Alloy Electrodes in Acidic Media

The cathodic reduction of NO in 1.0 M HClO₄ is investigated by voltammetry at pure Ni and Cu electrodes, and three Cu‐Ni alloy electrodes of varying composition, all configured as rotated disks. Voltammetric data obtained using these hydrodynamic electrodes demonstrate significantly improved activity for NO reduction at Cu‐Ni alloy electrodes as compared to the pure Ni and Cu electrodes. This observation is explained on the basis of the synergistic benefit of different surface sites for adsorption of H‐atoms, generated by cathodic discharge of H⁺ at Ni‐sites, and adsorption of NO at Cu‐sites on these binary alloy electrodes. Koutecky‐Levich plots indicate that the cathodic response for NO at a Cu₇₅Ni₂₅ electrode corresponds to an 8‐electron reduction, which is consistent with production of NH₃. In comparison, the cathodic response at Cu₅₀Ni₅₀ and Cu₂₅Ni₇₅ electrodes corresponds to a 6‐electron reduction, which is consistent with production of NH₂OH. Flow injection data obtained using Cu₅₀Ni₅₀ and Cu₂₅Ni₇₅ electrodes with 100‐μL injections exhibit detection limits for NO of ca. 0.95 μM (ca. 95 pmol) and 0.60 μM (ca. 60 pmol), respectively.     

An azide‐bridged copper(II) complex: poly[piperazine‐1,4‐dium [tetra‐μ3‐azido‐κ12N1:N1:N1‐hexa‐μ2‐azido‐κ12N1:N1‐di‐μ2‐azido‐κ4N1:N3‐pentacopper(II)] tetrahydrate]

A new Cu^II–azide complex, {(C₄H₁₂N₂)[Cu₅(N₃)₁₂]·4H₂O}_n, has been synthesized by the reaction of piperazine, Cu(OAc)₂·2H₂O (OAc is acetate) and NaN₃. In the structure, μ₂‐1,1‐ and μ₃‐1,1,1‐azide anions bridge five Cu^II cations to form a linear pentanuclear cluster unit, which is further linked by μ₂‐1,1‐ and μ₂‐1,3‐azide anions to form a two‐dimensional condensed [Cu₅(N₃)₁₂]_n layer. The diprotonated piperazine and the solvent water molecules are hydrogen bonded to the coordination layers to form a three‐dimensional supramolecular network.     

Diamond‐ and Graphite‐Like Octacyanometalate‐Based Polymers Induced by Metal Ions

By using cyclohexane‐1,2‐diamine (chxn), Ni(ClO₄)₂ ? 6H₂O and Na₃[Mo(CN)₈] ? 4H₂O, a 3D diamond‐like polymer {[Ni^II(chxn)₂]₂[Mo^IV(CN)₈] ? 8H₂O}_n ( 1 ) was synthesised, whereas the reaction of chxn and Cu(ClO₄)₂ ? 6H₂O with Na₃[M^V(CN)₈] ? 4H₂O (M=Mo, W) afforded two isomorphous graphite‐like complexes {[Cu^II(chxn)₂]₃[Mo^V(CN)₈]₂ ? 2H₂O}_n ( 2 ) and {[Cu^II(chxn)₂]₃[W^V(CN)₈]₂ ? 2H₂O}_n ( 3 ). When the same synthetic procedure was employed, but replacing Na₃[Mo(CN)₈] ? 4H₂O by (Bu₃NH)₃[Mo(CN)₈] ? 4H₂O (Bu₃N=tributylamine), {[Cu^II(chxn)₂Mo^IV(CN)₈][Cu^II(chxn)₂] ? 2H₂O}_n ( 4 ) was obtained. Single‐crystal X‐ray diffraction analyses showed that the framework of 4 is similar to 2 and 3 , except that a discrete [Cu(chxn)₂]²⁺ moiety in 4 possesses large channels of parallel adjacent layers. The experimental results showed that in this system, the diamond‐ or graphite‐like framework was strongly influenced by the inducement of metal ions. The magnetic properties illustrate that the diamagnetic [Mo^IV(CN)₈] bridges mediate very weak antiferromagnetic coupling between the Ni^II ions in 1 , but lead to the paramagnetic behaviour in 4 because [Mo^IV(CN)₈] weakly coordinates to the Cu^II ions. The magnetic investigations of 2 and 3 indicate the presence of ferromagnetic coupling between the Cu^II and W^V/Mo^V ions, and the more diffuse 5d orbitals lead to a stronger magnetic coupling interaction between the W^V and Cu^II ions than between the Mo^V and Cu^II ions.     

Noble‐Metal‐Free Janus‐like Structures by Cation Exchange for Z‐Scheme Photocatalytic Water Splitting under Broadband Light Irradiation

Z‐scheme water splitting is a promising approach based on high‐performance photocatalysis by harvesting broadband solar energy. Its efficiency depends on the well‐defined interfaces between two semiconductors for the charge kinetics and their exposed surfaces for chemical reactions. Herein, we report a facile cation‐exchange approach to obtain compounds with both properties without the need for noble metals by forming Janus‐like structures consisting of γ‐MnS and Cu₇S₄ with high‐quality interfaces. The Janus‐like γ‐MnS/Cu₇S₄ structures displayed dramatically enhanced photocatalytic hydrogen production rates of up to 718 μmol g⁻¹ h⁻¹ under full‐spectrum irradiation. Upon further integration with an MnO_x oxygen‐evolution cocatalyst, overall water splitting was accomplished with the Janus structures. This work provides insight into the surface and interface design of hybrid photocatalysts, and offers a noble‐metal‐free approach to broadband photocatalytic hydrogen production.     

A tetranuclear copper(II) cluster: bis(μ‐4‐chlorobenzoato‐κ2O:O′)(4‐chlorobenzoato‐κ2O,O′)(4‐chlorobenzoato‐κO)tetrakis(μ3‐2‐pyridylmethanolato‐κ4N,O:O:O)tetracopper(II)

The title compound, [Cu₄(C₇H₄ClO₂)₄(C₆H₆NO)₄], consists of isolated tetranuclear clusters, where the Cu²⁺ cations are five‐ and sixfold coordinated by O atoms from the 4‐chlorobenzoate anions and by pyridine N and methanolate O atoms from bidentate 2‐pyridylmethanolate ligands. While three Cu atoms are six‐coordinated by an NO₅ donor set forming distorted octahedra, the fourth Cu atom is five‐coordinated by an NO₄ donor set forming a distorted tetragonal–pyramidal coordination around the Cu atom. The nucleus is a deformed cubane‐like Cu₄O₄ structure, with Cu...Cu distances in the range 3.0266 (11)–3.5144 (13) Å.