Tetranuclear Copper Cluster Research Articles

Two New Cubane-Type Tetranuclear Compounds of Copper(II), Nickel(II) Derived from Reduced Schiff Base Ligand: Syntheses, Structures and Magnetic Properties

Two tetranuclear complexes, [M(H3L)]4·X (1, M = Cu, X = 4,4′-dpdo; 2, M = Ni, X = DMF, H5L = 2-[(3,5-dibromo-2-hydroxybenzyl) amino]-2-(hydroxymethyl)propane-1,3-diol, 4,4′-dpdo is 4,4′-bipyridine-N,N′-dioxide, DMF = N,N′-dimethyl formamide), have been synthesized and characterized by elemental analysis, IR and X-ray single-crystal diffraction. Compound 1 features a centrosymmetric tetranuclear copper cluster which further constructed a 1D chain through a tetra-acceptor hydrogen bonds of 4,4′-dpdo molecule. Compound 2 having a P21 /n space group also exhibits a tetranuclear nickel cluster with a cubane topology in which the central Ni(II) ion and oxygen atoms from H3L2− occupy the alternate vertices of the cube. Magnetic properties of 1 and 2 in the 2–300 K have also been discussed. The tetranuclear cubanes cores display dominant ferromagnetic interactions.

Synthesis, Structure and Electrochemistry of Tetranuclear Oxygen-Centered Copper(II) Clusters with Acetylacetone and Benz-pyrazole Hydrolyzed Derivatives as Ligand

Two copper(II) clusters Cu(4)OCl(6)(pyrazole)4, 1, and Cu(4)OBr(6)(Br-pyrazole)4, 2, have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio) with CuX(2) (X = Cl for 1 and X= Br for 2) in methanol solutions. The structures of both clusters have been established by X-ray crystallography. The clusters contain four Cu, one O, six μ(2)-X atoms, and four pyrazole ligands. The pyrazoles was prepared in situ by the reaction of acetylacetone with benzohydrazide in methanol under reflux. In 2, the methine hydrogens of the pyrazole ligands have been replaced by bromine atoms. The four copper atoms encapsulate the central O atom in a tetrahedral arrangement. All copper atoms are five-coordinate and have similar coordination environments with slightly distorted trigonal bipyramidal geometry. The cyclic voltammogram of the clusters 1 and 2 show a one-electron quasi-reversible reduction wave in the region 0.485 to 0.731 V, and a one-electron quasi-reversible oxidation wave in the region 0.767 to 0.898 V. In 1, one irreversible oxidative response is observed on the positive of side of the voltammogram at 1.512 V and this can be assigned to Cu(II) to Cu(III) oxidation.

Construction of three coordination polymers based on tetranuclear copper(ii) clusters: syntheses, structures and photocatalytic properties

Three intriguing metal-cluster based coordination polymers (MCOFs) {[Cu4(OH)2(itp)2(btc)2(H2O)4][Cu(H2O)4(Hbtc)]2·4H2O}n (1), {[Cu4(OH)2(itp)2(btc)2]·2EtOH·2H2O}n (2) and {[Cu4(OH)2(itp)2(sip)2(H2O)4]·4H2O}n (3) were synthesized by the reaction of 1-imidazol-1-yl-3-(1,2,4-triazol-4-yl)propane (itp), 1,3,5-benzenetricarboxylate (btc) or 5-sulfoisophthalate (sip) and CuCl2 using a hydrothermal method. 1 consists of an unprecedented (3,4)-connected 2D network based on the tetranuclear copper(II) clusters [Cu4(μ3-OH)2] and Cu1 cores with a Schlafli symbol of (62·8)2(6·84·10) and an unprecedented 2D → 3D polythreaded motif. 2 shows an unusual (3,10)-connected 3D network based on the tetranuclear copper(II) cluster [Cu4(μ3-OH)2] with the Schlafli symbol of (3·4·5)2(34·46·510·615·710). 3 exhibits a 2D (4,4) network based on tetranuclear copper(II) clusters [Cu4(μ3-OH)2]. 1–3 are semiconducting in nature, with Eg of 2.29 eV (1), 2.27 eV (2) and 2.39 eV (3). 1–3 are universal and highly efficient photocatalysts for the degradation of organic dyes such as methyl orange (MO), methylene blue (MB) and rhodamine B (RhB) under UV irradiation, are very stable and easily separated from the reaction system for reuse.

Hepta- and tetra-nuclear copper(II) clusters self-assembled by cyano- and azacyano-carbanions

Two polynuclear copper(II) complexes with hydroxido-bridging ligands and polycyanide units, [Cu{Cu(tn)}6(μ2-OH)2(μ3-OH)4Cl2](tcm)4Cl2·2H2O (1) and [{Cu(bpy)}4(OH)4(dca)2](dca)2·bpy·2H2O (2) (tn=NH2(CH2)3NH2; tcm−=[C(CN)3]−, bpy=2,2′-bipyridyl, dca−=[N(CN)2]−) have been prepared by one-pot reactions. The structure of 1 consists of a centrosymmetric heptanuclear ion [Cu{Cu(tn)}6(μ2-OH)2(μ3-OH)4Cl2]6+. The tcm− and the halide anions which appear as counter-ions in the formula unit, play an important role in the stabilization of the complex since the hydrogen bonding between nitrogen atoms of the tcm− anion and halide anions, and hydrogen atoms of the terminal water molecule and of the bridging hydroxido ligands generate an overall three-dimensional structure. The crystal structure of 2 is essentially built on discrete centrosymmetric tetranuclear [{Cu(bpy)}4(μ2-OH)2(μ3-OH)2(dca)2]2+ units including two μ2- and two μ3-OH ligands. As observed for 1, the dca− anions form a network of hydrogen bonding between their nitrogen atoms and hydrogen atoms of water molecules generating a two-dimensional structure. The magnetic susceptibility data indicate antiferromagnetic interactions in 1 and ferromagnetic ones in 2.

Synthesis, Crystal Structure, and Electroconducting Properties of a 1D Mixed-Valence Cu(I)–Cu(II) Coordination Polymer with a Dicyclohexyl Dithiocarbamate Ligand

A new mixed-valence Cu(I)–Cu(II) 1D coordination polymer, [CuI4CuIIBr4(Cy2dtc)2]n, with an infinite chain structure is synthesized by the reaction of Cu(Cy2dtc)2 (Cy2dtc− = dicyclohexyl dithiocarbamate, C13H22NS2) with CuBr·S(CH3)2. The as-synthesized polymer consists of mononuclear copper(II) units of CuII(Cy2dtc)2 and tetranuclear copper(I) cluster units, CuI4Br4. In the cluster unit, all the CuI ions have distorted trigonal pyramidal coordination geometries, and the CuI–CuI or CuI–CuII distances between the nearest copper ions are shorter than the sum of van der Waals radii for Cu–Cu.

A metal-organic framework constructed using a flexible tripodal ligand and tetranuclear copper cluster for sensing small molecules.

A new porous metal-organic framework (MOF) {[Cu4(OH)2(tci)2(bpy)2]·11H2O} (1) based on a tetranuclear copper cluster with intracluster antiferromagnetic interactions was synthesized. Quartz crystal microbalance (QCM) sensor studies reveal sensitive and selective sensing for small molecules.

Construction of Cu(ii), Zn(ii) and Cd(ii) metal–organic frameworks of bis(1,2,4-triazol-4-yl)ethane and benzenetricarboxylate: syntheses, structures and photocatalytic properties

Three coordination polymers {[Cu4(OH)2(btre)(1,2,3-btc)2(H2O)2]·2H2O}n (1), {[Zn4(OH)2(btre)(1,2,3-btc)2(H2O)4]·4H2O}n (2) and {[Cd3(btre)(1,2,3-btc)2(H2O)3]·3H2O}n (3) were synthesized by the hydrothermal method using 1,2-bis(1,2,4-triazol-4-yl)ethane (btre), 1,2,3-benzenetricarboxylate (1,2,3-btc) and metal ions (Cu(II), Zn(II), and Cd(II)). 1 shows a (3,8)-connected 3D metal–organic framework based on the tetranuclear copper(II) cluster [Cu4(μ3-OH)2] with the point symbol of (4·52)3(44·55·612·73·83·9). 2 exhibits a (3,8)-connected 3D metal–organic framework based on the tetranuclear zinc(II) cluster [Zn4(μ3-OH)2] with the point symbol of (42·6)3(46·618·83·10). In 3, each [Cd3(1,2,3-btc)2(H2O)]n chain connects four adjacent identical [Cd3(1,2,3-btc)2(H2O)]n chains through the btre bridges in four different directions, leading to an unusual 3D network. 3 shows a 4-connected 66dia topological net based on the [Cd3(H2O)(COO)4] trimer Cd(II) clusters. The diverse structures demonstrate that the central metal ions play the key role in the assembly of coordination polymers. 1 and 2 show good photocatalytic activity for the degradation of methyl orange. The luminescence of 2 and 3 was investigated.

The copper(I) metal azolate framework showing unusual coordination mode for the 1,2,4-triazole derivative and photocatalytic activity.

A unique three-dimensional metal azolate framework containing a tetranuclear copper cluster constructed by six 1,2,4-triazole units was synthesized in which the 1,2,4-triazole units show unusual bridging "crevice" coordination mode with their 1- and 2-positioned sp(2) N-atoms as symmetrically bridging centers. The photocatalytic activities of as-prepared compound were tested by degradation of rhodamine-B (RB) under different light irradiation.

Syntheses, structures and photocatalytic properties of two coordination polymers based on bis(1,2,4-triazol-4-ylmethyl)benzene and multicarboxylates

Two coordination polymers {[Cu4(OH)2(btrb)2(btc)2]·4H2O}n (1) and {[Cd2(btrb)(adc)2(H2O)]·H2O}n (2) were synthesized with hydrothermal method and characterized (btrb=1,4-bis(1,2,4-triazol-4-ylmethyl)benzene, btc=1,3,5-benzenetricarboxylate, adc=1,3-adamantanedicarboxylate). 1 shows an unusual (3,10)-connected two-dimensional metal–organic framework based on the tetranuclear copper(II) cluster [Cu4(μ3-OH)2]. 2 is an interesting three-dimensional network based on the one-dimensional metal–organic nanotube. 1 shows good photocatalytic activity for the degradation of methyl blue (MB). The luminescence of 2 was investigated.

Evolution of an adenine-copper cluster to a highly porous cuboidal framework: solution-phase ripening and gas-adsorption properties.

The synthesis and directed evolution of a tetranuclear copper cluster, supported by 8-mercapto-N9-propyladenine ligand, to a highly porous three-dimensional cubic framework in the solid state is reported. The structure of this porous framework was unambiguously characterized by X-ray crystallography. The framework contains about 62 % solvent-accessible void; the presence of a free exocyclic amino group in the porous framework facilitates reversible adsorption of gas and solvent molecules. Oriented growth of framework in solution was also tracked by force and scanning electron microscopy studies, leading to identification of an intriguing ripening process, over a period of 30 days, which also revealed formation of cuboidal aggregates in solution. The elemental composition of these cuboidal aggregates was ascertained by EDAX analysis.

Two copper(II) complexes based on N,N′-bis(4-pyridinecarboxamide)-1,2-ethane and tricarboxylate ligands: a 5-fold interpenetrating 3 D network and a 1 D ribbon-like chain

Two Cu(II) coordination polymers [Cu3(4-bpye)(BTC)2(H2O)7]·2H2O (1) and [Cu2(4-bpye)(SIP)(OH)(H2O)2]·3H2O (2) [4-bpye = N,N′-bis(4-pyridinecarboxamide)-1,2-ethane, H3BTC = 1,3,5-benzenetricarboxylic acid, H3SIP = 5-sulfoisophthalic acid], have been hydrothermally synthesized. X-ray diffraction analysis reveals that complex 1 has a fivefold interpenetrating 3D coordination network structure based on 2D double layers, with a trinodal (2,3,3)-connected {10}{6 .102}2{62.10}2 topology. Complex 2 has a 1D ribbon-like chain based on tetranuclear copper clusters, 4-bpye ligands and SIP anions, such that adjacent chains are further linked by hydrogen bonding interactions to form a 3D supramolecular framework. The coordination modes of the tricarboxylate and 4-bpye ligands play important roles in the construction of the two complexes with different dimensionalities. The electrochemical behaviors of both complexes have been studied.

Two new octamolybdate-based hybrids constructed by dinuclear/tetranuclear metal-tetrazole clusters: Syntheses, structures and photoluminescence

Through hydrothermal reactions of d0 metal ions with 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole (HL), two new octamolybdate-based hybrids, namely, (H2L)2[Ag2(HL)2(β-Mo8O26)] (1) and [Cu4(HL)4(θ-Mo8O26)]·5H2O (2), have been prepared and structurally characterized. X-ray single-crystal analyses show that compound 1 consists of discrete H2L cations and infinite one-dimensional (1D) anionic chains [Ag2(HL)2(β-Mo8O26)]2− constructed by [β-Mo8O26]4− bridged via dinuclear clusters {Ag2(HL)2}2+. Compound 2 displays a 2D network generated by 1D cationic tetranuclear copper cluster chains {Cu4(HL)4}n and [θ-Mo8O26]4− clusters. In addition, luminescent properties of both compounds have been studied.

Reactions of Copper(II) Chloride in Solution: Facile Formation of Tetranuclear Copper Clusters and Other Complexes That Are Relevant in Catalytic Redox Processes

Mixing CuCl2⋅2 H2O with benzylamine in alcoholic solutions led to an extremely colorful chemistry caused by the formation of a large number of different complexes. Many of these different species could be structurally characterized. These include relatively simple compounds such as [Cu(L(1))4Cl2] (L(1) = benzylamine) and (HL(1))2[CuCl4]. Most interestingly is the easy formation of two cluster complexes, one based on two cluster units Cu4OCl6(L(1))4 connected through one [Cu(L(1))2Cl2] complex and one based on a cubane-type cluster ([Cu4O4](C11H14)4Cl4). Both clusters proved to be highly reactive in a series of oxidation reactions of organic substrates by using air or peroxides as oxidants. Furthermore, it was possible to isolate and structurally characterize ([Cu(L(1))Cl]3 and [Cu(benz2mpa)2]CuCl2 (benz2mpa = benzyl-(2-benzylimino-1-methyl-propylidene)-amine), two copper(I) complexes that formed in solution, demonstrating the high redox activity of the cluster systems. In addition, it was possible to solve the molecular structures of the compounds Cu4OCl6(MeOH)4, [Cu(MeOH)2Cl2], [Cu(aniline)2Cl2], and an organic side product (HC13 H19 NOCl). In fact all determined structures are of a known type but the chemical relation between these compounds could be explained for the first time. The paper describes these different compounds and their chemical equilibria. Some of these complexes seem to be relevant in catalytic oxidation reactions and their reactivity is discussed in more detail.

A novel 3D metal–organic coordination polymer constructed from two types of tetranuclear copper clusters and a flexible bispyridyl-based ligand with amide-(CH2)6 bridge

A new 3D metal–organic coordination polymer with an unusual 3,3,8,8-connected {4.5.6}4{42.58.612.73.83}{42.59.614.7.82} topology has been synthesized under hydrothermal condition, [Cu4(BTC)2(L)(μ3-OH)2(H2O)] · 6H2O (1) [L = N,N′-bis(3-pyridinecarboxamide)-1,6-hexane, H3BTC = 1,3,5-benzenetricarboxylic acid], which represents the first example of metal–organic frameworks based on two types of tetranuclear copper clusters [Cu4(μ3-OH)2(O2C-)6] and flexible bis-pyridyl-bis-amided based ligand. Moreover, the electrochemical behavior and magnetic property of 1 have been investigated.

Two novel 3D copper(II) complexes based on a rigid bis-pyridyl-bis-amide and two polycarboxylates mixed ligands: Assembly, structures and properties

Two novel three-dimensional (3D) copper(II) complexes [Cu3(3-bpcb)(1,2-BDC)2(μ2-OH)2] (1) and [Cu2(3-bpcb)1.5(SIP)(μ3-OH)]·H2O (2), based on a rigid bis-pyridyl-bis-amide ligand [3-bpcb=N,N′-bis(3-pyridinecarboxamide)-1,4-benzene] and two different polycarboxylates [1,2-H2BDC=1,2-benzenedicarboxylic acid, NaH2SIP=sodium 5-sulfoisophthalic acid] have been prepared under hydrothermal conditions. Single crystal X-ray diffraction analysis shows that complex 1 exhibits a 4-nodal mixed (3,4,4,5)-connected 3D structure with the (3·4·5)2(3·42·5·86)2(32·8·92·10)(42·82·102) Schläfli symbol, which is constructed from two-dimensional (2D) Cu(II)-μ2-OH-3-bpcb layers (3-bpcb: μ4-bridging coordination mode via two pyridyl nitrogen and two carbonyl oxygen atoms) and the 1,2-BDC bridging ligands. Complex 2 is also a 3D coordination polymer constructed from the μ2-bridging 3-bpcb ligands (via two pyridyl nitrogen atoms) and the 2D Cu(II)-μ3-OH-SIP sheets containing tetranuclear copper clusters, showing a novel 3-nodal (5,6,6)-connected (33·43·53·63·72·8)(33·43·53·6)(33·46·54·62) topology. The differences between the final 3D structures for complexes 1 and 2 might be attributed to the different aromatic polycarboxylates and the bis-pyridyl-bis-amide ligand with different coordination modes. Moreover, the electrochemical behavior of complex 1 and the fluorescence properties of the complexes 1–2 have been investigated.

Three tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole and different aromatic carboxylates: Assembly, structures, electrochemical and magnetic properties

Three new tetranuclear copper(II) cluster-based complexes constructed from 4-amino-1,2,4-triazole (atrz) and three types of aromatic carboxylates, [Cu4(μ3-OH)2(atrz)2(DNBA)6] (1), [Cu4(μ3-OH)2(atrz)2(1,3-BDC)3]·2H2O (2) and [Cu4(μ3-OH)2(atrz)2(SIP)2]·4H2O (3) (HDNBA=3,5-dinitrobenzoic acid, 1,3-H2BDC=1,3-benzenedicarboxylic acid and NaH2SIP=sodium 5-sulfoisophthalate), have been hydrothermally synthesized and structurally characterized. Complex 1 displays a single-molecular CuII4 cluster structure, which is further connected by the intermolecular hydrogen-bonding interactions to form a 2D supramolecular layer. In 2, there also exist tetranuclear CuII4 clusters, which are linked by the 1,3-BDC anions to give a 3D NaCl-type framework. In 3, the CuII4 clusters are connected by the carboxyl and sulfo groups of SIP anions to generate 3D (4,8)-connected framework with a (410·614·84)(45·6)2 topology. The atrz ligand conduces to the construction of tetranuclear copper(II) clusters and the carboxylates with different non-carboxyl substituent show important effects on the final structures of the title complexes. The electrochemical and magnetic properties of 1–3 have been investigated.

Synthesis and Structures of Copper(I) Complexes with Phosphino-Functionalized N-Heterocyclic Carbenes (NHCP) and Bis-N-Heterocyclic Carbenes (Bis-NHC)

New copper(I) complexes bearing N-phosphino- and N-phosphinomethyl-functionalized NHC ligands (NHCP systems) were synthesized and fully characterized. Using halide-containing copper(I) precursors, strikingly different structural motifs were found, dependent on the substitution pattern of the NHCP moiety. An interesting tetranuclear μ4-bridged copper(I) cluster (4b) is formed when CuBr·SMe2 is reacted with the N-phosphino-substituted ligand 1a, whereas the dinuclear complex 4a is formed in an analogous reaction with 1b. Dinuclear metallacycles (2a,b) were isolated and characterized by X-ray diffraction when the halide-free copper(I) precursor [Cu(CH3CN)4]PF6 was reacted with NHCP ligands 1a,b using the N-phosphinomethyl-substituted NHCP ligands 5a,b, as well as employing the bis-NHC ligands BIM and BIM-BMe2 (10a,b), respectively. The observed copper(I)–copper(I) distances are directly correlated with the size of the metallacycle formed. An unexpected strong influence upon the metal–metal separation was found for the charged complexes in 10a,b. Using directly N-tBu-substituted NHCP ligands led to formation of an electronically less favorable trans-C,C coordination at the copper(I) centers (3 and 6a), which inhibited the formation of a dimeric species in the case of 3.

The Role of the Coordination Modes of a Flexible Bis(pyridylamide) Ligand in the Topology of 2D Copper(II) Complexes

Two new two-dimensional copper(II) coordination polymers, [Cu(L)(BDC)]_H2O (1) and [Cu2(L)0:5(SIP)(OH)(H2O)] 2H2O (2) [L=N;N0-bis(3-pyridylamide)-1,6-hexane, H2BDC=1,3- benzenedicarboxylic acid, H3SIP=5-sulfoisophthalic acid (3,5-dicarboxybenzenesulfonic acid)], have been synthesized hydrothermally by self-assembly of the flexible bis-pyridyl-bis-amide ligand L and the aromatic polycarboxylate ligands H2BDC or H3SIP. X-Ray diffraction analysis reveals that complex 1 displays a metal-organic coordination layer with a binodal (3,5)-connected {42.67.8}{42.6} topology, in which the L ligands adopt a m2-bridging mode (via ligation of the pyridyl nitrogen atoms). Complex 2 also exhibits a layered network based on tetranuclear copper clusters [Cu4(μ3-OH)2(H2O)2(O2C-)4], L ligands and SIP anions, showing a binodal (4,8)-connected network with {414.610.84}{44.62} topology, in which the L ligands adopt a μ6-bridging coordination mode (via ligation of the pyridyl nitrogen and carbonyl oxygen atoms). Adjacent layers in 1 and 2 are further linked by hydrogen bonding interactions to form three-dimensional supramolecular frameworks. The electrochemical behavior of the two complexes in bulk-modified carbon paste electrodes has been investigated

Synthesis, structure, fluorescent and magnetic properties of a series of coordination polymers based on a long and flexible bis-triazole ligand

Using the long and flexible bis(4-(4H-1,2,4-triazol-4-yl)phenyl)methane (BTPM) as a ligand, six novel coordination polymers have been synthesized under hydrothermal conditions. {[Zn(BTPM)(HCOO)](NO3)·2.25H2O}n (1) and {[Cd(BTPM)(HCOO)](NO3)·H2O}n (2) exhibit 2D bi-wave layers with one dimensional microchannels of 9 × 9 A2, which can form 3D supramolecular structures by intermolecular hydrogen bonds. Both {[Zn2(BTPM)3(H2O)4](NO3)4·H2O}n (3) and {[Cd2(BTPM)3(H2O)4](NO3)4·3.5H2O}n (4) are composed of multiple pairs of interpenetrating (4,4) sheets. {[Cu8(μ4–O)(μ2–H2O)2(BTPM)12](ClO4)14·4H2O}n (5) and {[Co3(BTPM)3(H2O)6](NO3)6·7H2O}n (6) are 3D interpenetrating frameworks. In complex 5, a rare square planar tetra-coordinate oxygen (ptO) and two different tetranuclear copper(II) clusters, [Cu4(μ2–H2O)2N20] and [Cu4(μ4–O)N20], have been observed. Complex 6 shows a 6-connected topology based on linear trinuclear clusters. The fluorescent properties of 1–4, as well as the magnetic properties of 5 and 6 are studied.

A stable luminescent hybrid mesoporous copper complex–silica

Surfactant-assisted co-condensation of an emissive tetranuclear alkynyl-phosphine copper cluster with TEOS affords a hydrothermally stable blue-emitter mesoporous hybrid metal complex-silica material.