Tetranuclear Copper Cluster Research Articles

Research on Synthesis, Structure, and Catalytic Performance of Tetranuclear Copper(I) Clusters Supported by 2-Mercaptobenz-zole-Type Ligands.

Tetrahedral copper(I) clusters [Cu4(MBIZ)4(PPh3)2] (2), [Cu4(MBOZ)4(PPh3)4] (6) (MBIZ = 2-mercaptobenzimidazole, MBOZ = 2-mercaptobenzoxazole) were prepared by regulation of the copper-thiolate clusters [Cu6(MBIZ)6] (1) and [Cu8(MBOZ)8I]- (5) with PPh3. With the presence of iodide anion, the regulation provided the iodide-containing clusters [CuI4(MBIZ)3(PPh3)3I] (3) and [CuI4(MBOZ)3(PPh3)3I] (7). The cyclic voltammogram of 3 in MeCN (0.1 M nBu4NPF6, 298 K) at a scan rate of 100 mV s-1 shows two oxidation processes at Epa = +0.11 and +0.45 V with return waves observed at Epc = +0.25 V (vs. Fc+/Fc). Complex 3 has a higher capability to lose and gain electrons in the redox processes than complexes 2, 4, 4', 6, and 7. Its thermal stability was confirmed by thermogravimetric analysis. The catalytic performance of 3 was demonstrated by the catalytic transformation of iodobenzenes to benzonitriles using AIBN as the cyanide source. The nitrile products show potential applications in the preparation of 1,3,5-triazine compounds for organic fluorescence materials.

Electrocatalytic micro-environment regulation of ZIF-67 with broadened pore structure and unsaturated coordination sites for oxygen evolution reaction

The atomically precise mental nanoclusters have been widely explored in catalysis. However, the easy aggregation of clusters limits their application. The porous structure of metal-organic framework can prevent the aggregation and growth of clusters. In this work, a copper-phosphine complex: Cu2(dppm)2(PF6)2 (Cu2) was synthesized by one-pot method and then reacted with hydrogen sulfide to obtain a tetranuclear copper cluster: Cu4(S)(dppm)4(PF6)2 (Cu4). The two copper clusters were successfully introduced into Zeolitic imidazole frameworks-67 (ZIF-67) to form Cu2-ZIF-67 and Cu4-ZIF-67. It found that after the introduction of Cu cluster, the pore size of ZIF-67 was increased leading to more exposed Co2+ and more unsaturated coordination mental sites, which is beneficial for electrochemical oxygen evolution reaction (OER). The OER ability of pure ZIF-67 was enhanced after the introduction of Cu2 and Cu4 clusters, in which Cu4-ZIF-67 displayed the best electrochemical performance. At 10 mA cm−2, it requires an overpotential of 340 mV. The lower Tafel slope and smaller charge transfer resistance reflect its faster dynamic process. This work provides a new idea for the development of OER electrocatalysts.

Tetranuclear CuIICluster as the Ten Node Building Unit for the Construction of a Metal–Organic Framework for Efficient C2H2/CO2Separation

AbstractRational design of high nuclear copper cluster‐based metal–organic frameworks has not been established yet. Herein, we report a novel MOF (FJU‐112) with the ten‐connected tetranuclear copper cluster [Cu4(PO3)2(μ2‐H2O)2(CO2)4] as the node which was capped by the deprotonated organic ligand of H4L (3,5‐Dicarboxyphenylphosphonic acid). With BPE (1,2‐Bis(4‐pyridyl)ethane) as the pore partitioner, the pore spaces in the structure ofFJU‐112were divided into several smaller cages and smaller windows for efficient gas adsorption and separation.FJU‐112exhibits a high separation performance for the C2H2/CO2separation, which were established by the temperature‐dependent sorption isotherms and further confirmed by the lab‐scale dynamic breakthrough experiments. The grand canonical Monte Carlo simulations (GCMC) studies show that its high C2H2/CO2separation performance is contributed to the strong π‐complexation interactions between the C2H2molecules and framework pore surfaces, leading to its more C2H2uptakes over CO2molecules.

Tetranuclear CuII Cluster as the Ten Node Building Unit for the Construction of a Metal-Organic Framework for Efficient C2 H2 /CO2 Separation.

Rational design of high nuclear copper cluster-based metal-organic frameworks has not been established yet. Herein, we report a novel MOF (FJU-112) with the ten-connected tetranuclear copper cluster [Cu4 (PO3 )2 (μ2 -H2 O)2 (CO2 )4 ] as the node which was capped by the deprotonated organic ligand of H4 L (3,5-Dicarboxyphenylphosphonic acid). With BPE (1,2-Bis(4-pyridyl)ethane) as the pore partitioner, the pore spaces in the structure of FJU-112 were divided into several smaller cages and smaller windows for efficient gas adsorption and separation. FJU-112 exhibits a high separation performance for the C2 H2 /CO2 separation, which were established by the temperature-dependent sorption isotherms and further confirmed by the lab-scale dynamic breakthrough experiments. The grand canonical Monte Carlo simulations (GCMC) studies show that its high C2 H2 /CO2 separation performance is contributed to the strong π-complexation interactions between the C2 H2 molecules and framework pore surfaces, leading to its more C2 H2 uptakes over CO2 molecules.

A luminescent Cu4 cluster film grown by electrospray deposition: a nitroaromatic vapour sensor.

We present the fabrication and use of a film of a carborane-thiol-protected tetranuclear copper cluster with characteristic orange luminescence using ambient electrospray deposition (ESD). Charged microdroplets of the clusters produced by an electrospray tip deposit the clusters at an air-water interface to form a film. Different microscopic and spectroscopic techniques characterized the porous surface structure of the film. Visible and rapid quenching of the emission of the film upon exposure to 2-nitrotoluene (2-NT) vapours under ambient conditions was observed. Density functional theory (DFT) calculations established the favourable binding sites of 2-NT with the cluster. Desorption of 2-NT upon heating recovered the original luminescence, demonstrating the reusability of the sensor. Stable emission upon exposure to different organic solvents and its quenching upon exposure to 2,4-dinitrotoluene and picric acid showed selectivity of the film to nitroaromatic species.

Coupling strong photoluminescence and narrow band gap in a new tetranuclear copper cluster: Copper(I) iodide with dimethylamine

A novel tetranuclear Cu4I4 - organic amine cluster was synthesized, which was involved dimethylamine and cuprous iodide by hydrothermal, [C2H7N]4·Cu4I4 (1). The structure of compound 1 was determined by single crystal X-ray diffraction analysis and further characterized by elemental analysis, infrared spectroscopy, luminescence spectrum, powder X-ray diffraction, and thermogravimetric analysis. The result of solid-state luminescence spectrum testing of compound 1 displays strong yellow-light emission with λmax = 595 nm at room temperature, suggesting that compound 1 may be a good yellow light-emitting material. Specially, compound 1 exhibits a narrow band gap of 2.182 eV in semiconductor property and is chiefly contributed by inorganic Cu4I4 of [C2H7N]4·Cu4I4. These findings will contribute to an alternative pathway for exploring and developing novel fluorescence and semiconducting materials of the coordination compounds and related properties in other materials.

Modulating the ferroelectric performance by altering halogen anions in the crystals of tetranuclear copper-clusters

The ferroelectric performance of tetranuclear copper clusters can be modulated by altering the free halogen anions existing in the crystal structure.

Cu(I) coordination by N,N,N’,N’-tetra(di-ortho-anisylphosphanylmethyl) ethylene and propylene diamine: First example of a sandwiched CuCl-tetramer

New chelating α-aminophosphanes were obtained by Mannich-type reactions between formaldehyde, bis(2-methoxyphenyl)phosphane and aliphatic primary diamines bearing either a C2 or C3 carbon bridge between the amine functionalities. The reaction conditions, and in particular, the reaction sequence was found to significantly depend on the length of the carbon bridge of the diamine. Both obtained α-aminophosphanes (i.e. N,N,N’,N’-tetra(di-ortho-anisylphosphanylmethyl)-1,2-diaminoethane (L1) and N,N,N’,N’-tetra(di-ortho-anisylphosphanylmethyl)-1,3-diaminopropane (L2)) gave along with neocuproine cationic dinuclear Cu(I) complexes. The Cu(I) complex with L2 as ligand was further converted by the aid of NiCl2(DME) (DME = 1,2-dimethoxyethane) into a tetranuclear copper cluster showing a new type of CuCl-tetramer molecular structure. All synthesized compounds were characterized in solution by multinuclear NMR-, UV/Vis-spectroscopy, mass spectrometry and in the solid state by elemental analysis and some of them by single crystal structure analysis.

Synthesis, structure and properties of a 3D coordination polymer based on tetranuclear copper(I) and a tetra(triazole) ligand

A Cu(I) coordination polymer, {[Cu4Br(ttpe)3]Br2·(OH)}n (1), was prepared and characterized by single crystal X-ray diffraction analysis, EA, IR, PXRD, luminescence, optical band gaps and VB XPS spectra (ttpe = 1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene). 1 presents a two-fold interpenetrating (4,12)-connected 3D topology containing the [Cu4Br] tetranuclear copper(I) cluster building block with a point symbol of {44.62}3{424.640.82}. Eg, Ev and Ec of 1 were 2.20, 0.74 and −1.46 eV, respectively. 1 can act as a good photocatalyst for degradation of organic dyes. The photocatalytic mechanism was studied.

Synthesis and structural characterization of the formato bridged Cu(ii) cubane: Crystallographic evidence of atmospheric CO2 fixation as formate in a tertranuclear Cu(II) cluster

Fixation of atmospheric carbon-di-oxide (CO2) by metal complexes continuously receives a great deal of attention from the viewpoint of environmental concerns. Herein, a novel tetranuclear copper (II) cluster [Cu4 μ3-(mph)4 μ2-(HCO2)2] (ClO4)2.CH2Cl2 (1), synthesized using Methyl(6-hydroxymethyl)picolinate ligand (Hmhp) and Cu(ClO4)2·6H2O in the presence of triethylamine base, is reported where atmospheric CO2 is serendipitously trapped in the form of formato-bridging ligand. The single X-ray structural elucidation of the complex 1 reveals a Cu4O4 cubane cluster stabilized by four peripheral mhp ligands, all of which display μ3-η1: η1: η3 binding mode (each bridging ligand link three Cu (II) ions). Moreover, the cubane core was supported by two bridging formate groups, resulted from the reduction of atmospheric CO2. The two formate ions exhibit μ2-η1: η1 binding mode, bridges two Cu(II) atoms. All the Cu(II) ions in the cubane core possess distorted octahedral coordination geometry (CuN1O5). Based on the observed Cu···Cu interactions in the Cu4O4 cubane core, 1 can be categorized under [2+2+2] type of classification. In addition to the synthesis and characterization of 1, a mechanistic hypothesis for the reduction of atmospheric CO2 to formate is also proposed to highlight the future potential of similar complexes in CO2 fixation/conversion.

The bacterial copper resistance protein CopG contains a cysteine-bridged tetranuclear copper cluster

CopG is an uncharacterized protein ubiquitous in Gram-negative bacteria whose gene frequently occurs in clusters of copper resistance genes and can be recognized by the presence of a conserved CxCC motif. To investigate its contribution to copper resistance, here we undertook a structural and biochemical characterization of the CopG protein from Pseudomonas aeruginosa Results from biochemical analyses of CopG purified under aerobic conditions indicate that it is a green copper-binding protein that displays absorbance maxima near 411, 581, and 721 nm and is monomeric in solution. Determination of the three-dimensional structure by X-ray crystallography revealed that CopG consists of a thioredoxin domain with a C-terminal extension that contributes to metal binding. We noted that adjacent to the CxCC motif is a cluster of four copper ions bridged by cysteine sulfur atoms. Structures of CopG in two oxidation states support the assignment of this protein as an oxidoreductase. On the basis of these structural and spectroscopic findings and also genetic evidence, we propose that CopG has a role in interconverting Cu(I) and Cu(II) to minimize toxic effects and facilitate export by the Cus RND transporter efflux system.

Diversity of Coordination Modes in a Flexible Ditopic Ligand Containing 2-Pyridyl, Carbonyl and Hydrazone Functionalities: Mononuclear and Dinuclear Cobalt(III) Complexes, and Tetranuclear Copper(II) and Nickel(II) Clusters

Syntheses, crystal structures and characterization are reported for four new complexes [Cu4Br2(L)4]Br2 (1), [Ni4(NO3)2(L)4(H2O)](NO3)2 (2), [Co2(L)3](ClO4)3 (3) and [Co(L)2](ClO4) (4), where L− is the monoanion of the ditopic ligand N′-(1-(pyridin-2-yl)ethylidene)pyridine-2-carbohydrazide (LH) built on a picolinoyl hydrazone core fragment, and possessing a bidentate and a tridentate coordination pocket. The tetranuclear cation of 1·0.8H2O·MeOH is a strictly planar, rectangular [2 × 2] grid. Two 2.21011 L− ligands bridge adjacent CuII atoms on the short sides of the rectangle through their alkoxide oxygen atoms, and two 2.11111 ligands bridge adjacent CuII atoms on the long sides of the rectangle through their diazine groups; two metal ions are 5-coordinate and two are 6-coordinate. The tetranuclear cation of 2·0.2H2O·3EtOH is a square [2 × 2] grid. The two 6-coordinate NiII atoms of each side of the square are bridged by the alkoxide O atom of one 2.21011 L− ligand. The dinuclear cation of 3·0.8H2O·1.3MeOH contains two low-spin octahedral CoIII ions bridged by three 2.01111 L− ligands forming a pseudo triple helicate. In the mononuclear cation [Co(L)2]+ of complex 4, the low-spin octahedral CoIII center is coordinated by two tridentate chelating, meridional 1.10011 ligands. The crystal structures of the complexes are stabilized by a variety of π–π stacking and/or H-bonding interactions. Compounds 2, 3 and 4 are the first structurally characterized nickel and cobalt complexes of any form (neutral or anionic) of LH. The 2.01111 and 1.10011 coordination modes of L−, observed in the structures of complexes 3 and 4, have been crystallographically established for the first time in coordination complexes containing this anionic ligand. Variable-temperature, solid-state dc magnetic susceptibility and variable-field magnetization studies at 1.8 K were carried out on complexes 1 and 2. Antiferromagnetic metal ion···metal ion exchange interactions are present in both complexes. The study reveals that the cation of 1 can be considered as a practically isolated pair of strongly antiferromagnetically coupled (through the diazine group of L−) dinulear units. The susceptibility data for 2 were fit to a single-J model for an S = 1 cyclic tetramer. The values of the J parameters have been rationalized in terms of known magnetostructural correlations. Spectral data (infrared (IR), ultraviolet/visible (UV/VIS), 1H nuclear magnetic resonance (NMR) for the diamagnetic complexes) are also discussed in the light of the structural features of 1–4 and the coordination modes of the organic and inorganic ligands that are present in the complexes. The combined work demonstrates the ligating flexibility of L−, and its usefulness in the synthesis of complexes with interesting structures and properties.

Construction of (3,8)-connected three-dimensional cobalt(II) and copper(II) coordination polymers with 1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene and benzene-1,3,5-tricarboxylate ligands.

Coordination polymers (CPs) have been widely studied because of their diverse and adjustable topologies and wide-ranging applications in luminescence, chemical sensors, magnetism, photocatalysis, gas adsorption and separation. In the present work, two coordination polymers, namely poly[(μ5-benzene-1,3,5-tricarboxylato-κ6O1:O1':O3:O3:O5,O5'){μ3-1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene-κ3N:N':N''}di-μ3-hydroxido-dicobalt(II)], [Co2(C9H3O6)(OH)(C12H12N6)]n or [Co2(btc)(OH)(mtrb)]n, (1), and poly[[diaquabis(μ3-benzene-1,3,5-tricarboxylato-κ3O1:O3:O5)bis{μ3-1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene-κ3N:N':N''}tetra-μ3-hydroxido-tetracopper(II)] monohydrate], {[Cu4(C9H3O6)2(OH)2(C12H12N6)2(H2O)2]·H2O}n or {[Cu4(btc)2(OH)2(mtrb)2(H2O)2]·H2O}n, (2), were synthesized by the hydrothermal method using 1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene (mtrb) and benzene-1,3,5-tricarboxylate (btc3-). CP (1) exhibits a (3,8)-coordinated three-dimensional (3D) network of the 3,8T38 topological type, with a point symbol of {4,5,6}2{42·56·616·72·82}, based on the tetranuclear hydroxide cobalt(II) cluster [Co4(μ3-OH)2]. CP (2) shows a (3,8)-coordinated tfz-d topology, with a point symbol of {43}2{46·618·84}, based on the tetranuclear hydroxide copper(II) cluster [Cu4(μ3-OH)2]. The different (3,8)-coordinated 3D networks based on tetranuclear hydroxide-metal clusters of (1) and (2) are controlled by the different central metal ions [CoII for (1) and CuII for (2)]. The thermal stabilities and solid-state optical diffuse-reflection spectra were measured. The energy band gaps (Eg) obtained for (1) and (2) were 2.72 and 2.29 eV, respectively. CPs (1) and (2) exhibit good photocatalytic degradation of the organic dyes methylene blue (MB) and rhodamine B (RhB) under visible-light irradiation.

Temperature-dependent crystal structure and fluorescence properties of a tetranuclear copper(I) cluster from in situ [2 + 3] cycloaddition synthesis

Hydrothermal reaction of CuSO4·7H2O and NaN3 with 2-cyanothiophene in aqueous ethanol yielded a novel tetranuclear copper(I) polymer, {[Cu4(tptz)4]·0.5(C2H6O)}n (1) (Htptz = 5-(thiophen-2-yl)-1H-tetrazole). The tptz ligand in the complex was generated through an in situ [2 + 3] cycloaddition reaction involving the cyano groups of the precursor 2-cyanothiophene. In a rare example, three different geometries of Cu(I) cations, namely the linear, triangle, and tetrahedron geometries of Cu(I) centers, are created and linked by Htptz ligands into a 1-D ladder structure. Additionally, 1 exhibits strong blue fluorescence (with λ = 467 nm) at room temperature in the solid state.

Structure features, thermal analysis, model and experiment magnetic behavior of tetranuclear oxo and sulfato bridged copper (II) aggregate

The novel tetranuclear copper (II) cluster namely (C5H7N2)2[Cu4(µ4-O)(µ3-SO4)4(C5H6N2)4] (1) was obtained by the hydrothermal reaction of copper (II) sulfate and the monodentate 4-aminopyridine ligand. Single-crystal X-ray diffraction indicated that compound 1 crystallizes in the monoclinic system, space group C2/c, a=25.827 (5)Å, b=10.657 (5)Å, c=19.838 (5)Å, β=121.195 (5)°, V=4671 (3)Å3 and Z=4. The discrete [Cu4(µ4-O)(µ3-SO4)4(C5H6N2)4]2− anion present in (1) contains Cu4(µ4-O) tetrahedra with the copper centres held together by four sulfate groups in two different coordinated modes: η1.η1.η1.μ3:3.1110 and η2.η1.μ3:3.2100 (Harris notation). Again, the structural arrangement and the intermolecular interactions such as hydrogen-bonding are discussed from which supramolecular assembly was formed. The thermal behavior of the compound, studied by TG-DSC, showed that the successive decomposition stages of precursor lead to the formation of intermediate phases during heating giving rise to the copper oxide as a final product at 700°C. Characteristic IR bands are discussed in terms of the known structure of (1). The magnetic properties of (1) have been studied by variable temperature dc magnetic susceptibility techniques. Using an idealized geometry of the tetranuclear cluster the magnitude of exchange coupling constants is examined. The calculations within the simplified model reveal a relatively strong superexchange interaction between the Cu(II) ions (on the order of a 100cm−1) indicating a substantial anisotropy with the apical coupling being ferromagnetic while the equatorial coupling favoring an antiferromagnetic arrangement of the spin components.

Synthesis, Structure and Properties of a Novel Tetranuclear Copper Cluster-Based Polymer with Di-Schiff-Base

A novel tetranuclear cluster-based polymer {[Cu4(L)2(NO3)2(DMF)2]·(CH2Cl2)2}n (1, H3L = (1Z,2E,N′E)-N′,2-bis(2-hydroxybenzylidene)hydrazinecarbohydrazonic acid) was synthesized through diffusion method. The structure of 1 was characterized by elemental analysis, IR, and single crystal X-ray diffraction. 1 is tetranuclear copper cluster which further constructed 1-D chain through double Cu–O bonds. Luminescent and magnetic properties of 1 have been studied. Hirshfeld surfaces analysis revealed that complex 1 was supported mainly by H···H, O···H and H···Cl intermolecular interactions.

Spectroscopic Definition of the CuZ° Intermediate in Turnover of Nitrous Oxide Reductase and Molecular Insight into the Catalytic Mechanism.

Spectroscopic methods and density functional theory (DFT) calculations are used to determine the geometric and electronic structure of CuZ°, an intermediate form of the Cu4S active site of nitrous oxide reductase (N2OR) that is observed in single turnover of fully reduced N2OR with N2O. Electron paramagnetic resonance (EPR), absorption, and magnetic circular dichroism (MCD) spectroscopies show that CuZ° is a 1-hole (i.e., 3CuICuII) state with spin density delocalized evenly over CuI and CuIV. Resonance Raman spectroscopy shows two Cu-S vibrations at 425 and 413 cm-1, the latter with a -3 cm-1 O18 solvent isotope shift. DFT calculations correlated to these spectral features show that CuZ° has a terminal hydroxide ligand coordinated to CuIV, stabilized by a hydrogen bond to a nearby lysine residue. CuZ° can be reduced via electron transfer from CuA using a physiologically relevant reductant. We obtain a lower limit on the rate of this intramolecular electron transfer (IET) that is >104 faster than the unobserved IET in the resting state, showing that CuZ° is the catalytically relevant oxidized form of N2OR. Terminal hydroxide coordination to CuIV in the CuZ° intermediate yields insight into the nature of N2O binding and reduction, specifying a molecular mechanism in which N2O coordinates in a μ-1,3 fashion to the fully reduced state, with hydrogen bonding from Lys397, and two electrons are transferred from the fully reduced μ4S2- bridged tetranuclear copper cluster to N2O via a single Cu atom to accomplish N-O bond cleavage.

Stimuli-responsive Luminescent Copper(I) Complexes for Intelligent Emissive Devices

Extensive studies of luminescent copper(I) complexes were conducted, revealing that some of them exhibit interesting chromic luminescence in response to external stimuli such as temperature, vapor, light, and mechanical force. In this review, recent progress in the field of luminescent chromic copper(I) complexes is discussed. Tetranuclear copper(I) clusters with a cubane-type {Cu4I4} core are the most prominent group, which shows thermochromic, vapochromic, and mechanochromic luminescence, and their responsiveness to external stimuli greatly depends on coordinating organic ligands. Coordination polymerization of copper(I) cluster cores using organic linkers provides new luminescent thermochromic and vapochromic materials with behavior strongly dependent on the flexibility of the framework. The diversity of the cluster core structure and the lability to the ligand exchange are also useful to derive unique behaviors of photochromic and vapochromic response. In addition to such stimuli-responsive luminescen...

A reactive oxygen species-generating, cyclooxygenase-2 inhibiting, cancer stem cell-potent tetranuclear copper(ii) cluster.

Tetranuclear copper(ii) complexes containing multiple diclofenac and Schiff base moieties, 1-4, are shown to kill bulk cancer cells and cancer stem cells (CSCs) with low micromolar potency. The most effective complex, 1, elicits its cytotoxic effect by elevating the intracellular reactive oxygen species (ROS) levels and inhibiting cyclooxygenase-2 (COX-2) expression.

Synthesis, structure and photocatalytic properties of an unusual tetranuclear copper(II) coordination polymer

An unusual coordination polymer [Cu4(OH)2(otrb)2(sip)2]n (1) was synthesized by the hydrothermal method (otrb=1,2-bis(1,2,4-triazol-4-ylmethyl)benzene, sip=5-sulfoisophthalate). The tetranuclear copper(II) clusters [Cu4(OH)2] are bridged by the double sip and double otrb ligands to form an unusual 2D sql network. The adjacent 2D networks parallel interpenetrate each other to form intriguing 2-fold interpenetrated network. The photocatalytic degradation rates of methyl orange (MO), methylene blue (MB) and rhodamine B (RhB) are 94.4%, 91.2% and 86.6% at 180min using photocatalyst 1. 1 is a highly efficient and universal photocatalyst for the degradation of the organic dyes.