Hexanuclear Copper Research Articles

Hexa- and polynuclear copper(II) coordination compounds based on the carbonato bridge: Synthesis, crystal structures and magnetic properties

The crystal structures of polynuclear copper(II) complexes containing the bidentate bpy ligand (bpy = 2,2′-bipyridine) with varied coordination modes of the carbonato bridging ligand, a hexanuclear compound [Cu 6(bpy) 10(μ-OH) 2(μ-CO 3) 2](CF 4SO 3) 6(DMF) 2(H 2O) 4 ( 1) and a polymeric compound {[Cu 3(bpy) 3(μ-OH) 2(μ-CO 3) 2](H 2O) 6.5} n ( 2) are described. Compound 1 consists of the di-μ-hydroxido-bis(2,2′-bipyridine)copper(II) groups coordinated with trans-axially at each copper atom by [μ-carbonato-bis(bpy)copper(II)] moieties, forming a hexanuclear copper(II) compound. Each copper(II) ion has a distorted square–pyramidal environment in which three Cu(II) atoms are linked through oxygen atoms of the bridged ligand by the μ 3-η 2:η 1-CO 3 coordinated mode. Compound 2 consists of two independent di-μ-hydroxido-bis(2,2′-bipyridine)copper(II) dinuclear units which are connected to the central moiety by two different coordination modes of the carbonate bridging ligands, μ-η 1:η 1 ( anti–anti) and μ-η 2:η 1-CO 3 configurations. Each Cu(II) ion has a distorted square–pyramidal geometry. The repeating units give rise to a one-dimensional chain along b-axis. The lattice structures are stabilized by stacking interaction between pyridine groups of bpy chelated ligands of different units. The spectroscopic properties (IR, Reflectance and EPR spectra) and the magnetic susceptibility data of both compounds are investigated.

Synthesis, Structure and Magnetic Properties of a Novel Hexanuclear Copper Methylsiloxane Complex

AbstractA new hexanuclear copper(II) sandwich complex based on two 12‐membered macrocyclic methylsiloxanolate ligands, [Cu6{(MeSiO2)6}2]·6DMF, was synthesized and characterized by single‐crystal X‐ray diffraction analysis and magnetic measurements. The cluster compound crystallizes in the monoclinic system, space group P21/n (No. 14), with a = 13.3728(5) Å, b = 15.4281(7) Å, c = 17.4335(7) Å, β = 98.932(3)° and Z = 2. The unit cell contains two identical molecular clusters, each consisting of six interacting Cu2+ (S = ${1 \over 2}$) ions. Within the cluster the six oxygen‐bridged Cu2+ ions are arranged in an almost regular hexagon. An analysis of the high‐temperature part of the magnetic susceptibility reveals that the complex has a strong average ferromagnetic Cu–Cu exchange interaction of |Jav/kB| = (50.4 ± 1) K with a high‐spin S = 3 ground state. A satisfactory fit for the magnetic susceptibility and the magnetization in the whole accessible temperature range is obtained from a Heisenberg model with nonuniform exchange couplings within a ring, corresponding to a system of two weakly coupled trimers with a ferromagnetic intratrimer exchange coupling of |J/kB| = 72.5 K and a ferromagnetic intertrimer exchange coupling of |J′/kB| = 7 K. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Solvothermal in situ formation of a hexanuclear copper(I) complex with 2-thiolate- N, N′-dimethylnicotinamide

Solvothermal reaction of 2-mercaptonicotinic acid (H L 1) with copper(II) nitrate in DMF/methanol medium leads to the production of a novel hexanuclear complex [Cu( L 2)] 6 · (H 2O) 2 ( 1), in which in situ formation of an anionic ligand 2-thiolate- N, N′-dimethylnicotinamide ( L 2) and reduction of copper(II) to copper(I) are observed. X-ray single-crystal structure of 1 reveals that each copper(I) center adopts a trigonal geometry provided by two thiolate and one pyridyl groups from three separated L 2 ligands. As a result, six copper(I) ions are interconnected by six μ 3– L 2 bridges to afford a hexanuclear cluster, in which the octahedral Cu 6 core is stabilized by significant cuprophilic interactions.

The First Hexanuclear Copper(I) Carboxylate: X-ray Crystal Structure and Reactivity in Solution and Gas-Phase Reactions

The carboxylate ligand-exchange reaction of copper(I) trifluoroacetate by 3,5-difluorobenzoate yielded a new product, [Cu(O2C(3,5-F)2C6H3)] (1). Single crystals of 1 suitable for X-ray structural characterization were obtained by sublimation-deposition procedures at 230 degrees C. An X-ray diffraction study revealed a remarkable planar hexanuclear copper(I) core supported by bridging carboxylates, the first such structural type among other known copper(I) carboxylates. The Cu...Cu distances within the core range from 2.7064(8) to 2.8259(8) A and fall into the category of cuprophillic interactions. The hexacopper unit remains intact upon gas-phase deposition with a planar polyarene, coronene (C24H12), to give [Cu6(O2C(3,5-F)2C6H3)6](C24H12) (2). Density functional theory calculations suggest the latter compound to be a cocrystallization product having electrostatic interactions between the hexacopper complex and coronene. However, cocrystallization affects the photophysical properties of 2. While copper(I) 3,5-difluorobenzoate (1) exhibits photoluminescence at ca. 554 nm (lambda(ex) = 350 nm) in the solid state, compound 2 is nonluminescent at room temperature in the visible region. Gas-phase and solution reactions of 1 with alkyne ligands, diphenylacetylene (C14H10) and 1,4-bis(p-tolylethynyl)benzene (C24H18), result in the rupture of the [Cu6] core to afford dinuclear organometallic copper(I) complexes. The latter have a dimetal core cis-bridged by two carboxylate groups with acetylene ligands eta(2)-coordinated to each copper(I) center.

Combination of Lacunary Polyoxometalates and High-Nuclear Transition Metal Clusters under Hydrothermal Conditions. 3. Structure and Characterization of [Cu(enMe)2]2{[Cu(enMe)2(H2O)]2[Cu6(enMe)2(B-a-SiW9O34)2]}·4H2O

A novel sandwich-type polyoxometalate incorporating a unique hybrid hexanuclear copper cluster, [Cu(enMe)2]2{[Cu(enMe)2(H2O)]2[Cu6(enMe)2(B-a-SiW9O34)2]}.4H2O (1, enMe=1,2-diaminopropane), has been hydrothermally synthesized and structurally characterized by the elemental analyses, IR spectroscopy, TG analysis, magnetic properties, and single-crystal X-ray diffraction analysis. Crystal data for 1: triclinic, P; a=12.5105(2), b=14.3710(2), c=17.2687(2) A; alpha=98.834(1), beta=110.744(1), gamma=104.711(1) degrees; V=2704.57(7) A3; rho=3.646 g/cm3; Z=1. X-ray crystallographic study shows that the molecular structure of 1 contains 10 copper ions: Six of them form an unprecedented inorganic-organic hybrid Cu6 cluster via edge-sharing combination of two CuO6 octahedra, two CuO5, and two CuO3N2 square pyramids and are encapsulated between two {B-a-SiW9O34} units. Two of them form two [Cu(enMe)2(H2O)]2+ complexes and further attach to the two {B-a-SiW9O34} units via two Cu-O=W bridges, acting as a decorated role. The remaining two form isolated [Cu(enMe)2]2+ complexes playing roles of charge-compensation and space-fillers. Magnetization measurement reveals that the hexanuclear copper cluster exhibits overall ferromagnetic interactions.

Self-assembly of a High-Nuclearity Chloride-Centered Copper(II) Cluster. Structure and Magnetic Properties of [Au(PPh3)2][trans-Cu6(μ-OH)6{μ-(3,5-CF3)2pz}6Cl

A chloride-centered hexanuclear copper(II) pyrazolate [Au(PPh3)2][trans-Cu6(micro-OH)6[micro-(3,5-CF3)2pz]6Cl] is isolated from the reaction of the trinuclear copper(I) pyrazolate [Cu3[micro-(CF3)2pz]3] with PPh3AuCl and Ph3P in moist air. The six copper atoms are bridged by pyrazolate and hydroxyl ligands, above and below the copper plane. The chloride anion exists at the center of the planar cavity formed by the copper atoms with Cu-Cl distances of 3.02-3.13 A. The magnetic susceptibility measurements show a strong antiferromagnetic coupling between the copper centers with an estimated exchange constant of J approximately 650 cm-1.

Structure of the hexanuclear Cu(II) β-diketonate complex

The structure of the hexanuclear copper(II) β-diketonate complex with gfa (hexafluoroacetylacetone) and dpm (dipivalylmethanate) ligands was studied by low-temperature (T = 100 K) X-ray diffraction. Crystal data for Cu6(gfa)4(dpm)4(OH)4 [C64H84Cu6F24O20]: a = 28.2364(7) A, b = 12.8072(3) A, c = 24.7199(7) A, β= 115.900(1)°, V = 8041.5(4) A3, space group C2/m, Z = 4, d calc 1.661 g/cm3. The coordination polyhedra of the copper atoms — squares and octahedra — are formed by the oxygen atoms of the gfa and dpm ligands and groups. In all cases, the Cu-O distances vary from 1.89 A to 2.13 A. The complexes follow the sites of the rhombohedral sublattice with the parameters a c ≈ 14.4 A and a c ≈ 61.5°.

A three-dimensional ferromagnet based on linked copper–azido clusters

Two novel three-dimensional coordination polymers [Cu(6)(N(3))(12)(N-Eten)(2)](n) (1) (N-Eten=N-ethylethylenediamine) and {[Cu(9)(N(3))(18)(1,2-pn)(4)].H(2)O}(n) (2) (1,2-pn=1,2-diaminopropane) have been synthesized by the self-assembly reactions of Cu(NO(3))(2).3H(2)O, NaN(3) and small diamine ligands. Their molecular structures were determined by single-crystal X-ray diffraction. Complex 1 is composed of a neutral 3D coordination framework based on unprecedented hexanuclear copper(ii) clusters which features three types of bridging modes for azide (mu-1,1, mu-1,3 and mu-1,1,3). Complex 2 is a novel 3D coordination polymer featuring octanuclear copper-azido clusters and [Cu(diamine)(2)](2+) units which are linked by azido bridges. Magnetic studies for complex show ferromagnetic ordering at 3.5 K, where the azido bridges mediate ferromagnetic coupling between adjacent Cu(II) ions. The magnetic data for 1 were fitted to a uniform hexanuclear copper model which yielded g=2.21, J=6.26 cm(-1), zJ'=0.39 cm(-1). Complex 2 shows ferromagnetic coupling in the octanuclear unit and antiferromagnetic interaction between neighboring units.

A functionalized polyoxometalate by hexanuclear copper–amino acid coordination complexes

A new functionalized polyoxometalate by transition metal–amino acid coordination complexes, H 4[Na(H 2O) 2][Cu 6Na(gly) 8(H 2O) 2][BW 12O 40] 2 · 13H 2O ( 1) (gly = glycine) has been synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, and single crystal X-ray diffraction. Compound 1 possesses a 3D framework, which is built up of [BW 12O 40] 5− building blocks, hexanuclear [Cu 6Na(gly) 8] coordination clusters and Na + ions. Furthermore, magnetic measurements show ferromagnetic interactions for compound 1.

Porous material for absorption and luminescent detection of aromatic molecules in water

A two-dimensional porous framework, which was formed from neutral discrete hexanuclear copper clusters via self-assembly, exhibited highly selective absorption of aromatic molecules in water with special fluorescent response.

A Windmill-Shaped Hexacopper(II) Molecule Built Up by Template Core-Controlled Expansion of Diaquatetrakis(μ2-adeninato-N3,N9)dicopper(II) with Aqua(oxydiacetato)copper(II)

The windmill-shaped hexanuclear copper(II) cluster {(H(2)O)(2)Cu(2)(mu(3)-(Ade)(4)[Cu(oda)(H(2)O)](4)}.6H(2)O (1-o) has been synthesized in aqueous medium by in situ core-controlled expansion of the neutral building block Cu(2)(mu(2)-N3,N9-Ade)(4)(H(2)O)(2) (2) with Cu(oda)(H(2)O) (3-o) (Ade = adeninato(1-) and oda = oxydiacetato(2-) ligands). Crystal data for 2-b (2.5H(2)O): triclinic, space group P(-)1; a = 9.374(1), b = 9.440(1), c = 10.326(1) A; alpha = 78.72(1), beta = 76.77(1), gamma = 63.51(1) degrees ; final R(1) = 0.059; T = 100(2) K. Crystal data for 1-o: monoclinic, space group P2(1)/n; a = 15.203(2), b = 10.245(1), c = 19.094(2) A; beta = 101.61(1) degrees ; final R(1) = 0.049; T = 293(2) K. The X-shaped hexanuclear molecule consists of a central core (2) and four terminal arms (3-o) linked together by bridging mu(3)-N3,N7,N9-Ade ligands. There are three crystallographic independent metal atoms (two terminals, one central). All Cu(II) atoms exhibit a 4 + 1 coordination, of which one is an aqua apical ligand. The basal coordination sets complete the CuN(4) + O or CuO(3)N + O chromophores for the central or terminal metal atoms, respectively. Thermal stability and spectral and magnetic properties were also studied. Analogous compounds to 1-o with tridentate or tripodal tetradentate ligands L(2-), instead of oda, have also been synthesized.

One- and Two-Dimensional Coordination Polymers Constructed from Bicapped Keggin Mixed Molybdenum−Vanadium Heteropolyoxoanions and Polynuclear Copper(I) Clusters Bridged by Asymmetrical Bipyridine (2,4‘-bipy and 2,3‘-bipy) Ligands

Two novel trimetallic coordination polymers containing bridging bicapped Keggin mixed Mo/V polyoxoanions and asymmetrical aromatic amine bridging ligands 2,3‘-bipyridine (2,3‘-bipy) or 2,4‘-bipyridine (2,4‘-bipy), [CuI6(2,3‘-bipy)6(2,3‘-bipy-2‘-O)2][VIV2MoV5MoVI7O38(PO4)] [2,3‘-bipy-2‘-OH = 3-(pyridin-2-yl)pyridin-2-ol] (1) and [CuI5(2,4‘-bipy)6(OH)][PMoVI8VV3VIVO40(VIVO)2]·1.5H2O (2), have been prepared under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Gillard type hydration for the 2,3‘-bipy ligand was observed during synthesis of 1, which happens on the 2‘-carbon atom rather than on the α-carbon atom of the coordinated nitrogen atom in the 2,3‘-bipy ligand. Complex 1 is constructed from an alternatively arranged bivanadyl capped α-Keggin polymolybdate anion [VIV2MoV5MoVI7O38(PO4)]4- and double 2,3‘-bipy ligand bridged trinuclear copper(I) cluster [CuI3(2,3‘-bipy)3(2,3‘-bipy-2‘-O)]2+, forming a one-dimensional (1D) ribbon structure. The two-dimensional (2D) extended layer structure of 2 is composed of another type of bicapped Keggin mixed molybdenum−vanadium polyoxoanion [PMoVI8VV3VIVO40(VIVO)2]4- and copper(I) coordination polymer cation chain [CuI5(2,4‘-bipy)6(OH)]4+; the latter consists of a 2,4‘-bipy ligand bridged hexanuclear copper(I) cluster [CuI5(2,4‘-bipy)6]5+ linked by double hydroxyl groups.

Synthesis, Structure and Magnetic Properties of a Novel Linear CuII‐Trimer Complex

AbstractA new hexanuclear copper(II) sandwich complex based on two 10‐membered macrocyclic phenylsiloxanolate ligands, {Cu6[(C6H5SiO2)5]2(OH)2(C10H8N2)2}·4(DMF)·3(H2O) (1), was synthesized and characterized by single‐crystal X‐ray diffraction and measurements of the magnetic susceptibility and isothermal magnetization. The cluster compound crystallizes in the triclinic system, space group P$\bar {1}$ (No. 2), with a = 14.925(3) Å, b = 16.745(2) Å, c = 23.053(3) Å, α = 83.079(9)°, β = 84.836(13)°, γ = 65.019(17)°, and Z = 2. The unit cell contains two identical molecules, each consisting of six interacting Cu2+ (S = 1/2) ions. Within the molecule, the six Cu2+ ions are arranged in two almost linear, parallel trimers. While pairs of oxygen atoms link the Cu2+ ions within the trimers, single oxygen atoms residing at the ends of the trimers provide the strongest intertrimer bonds. Magnetic measurements reveal an antiferromagnetic intratrimer exchange interaction, J/kB = 85 K, as the dominant magnetic coupling of the complex. By introducing a weak antiferromagnetic intertrimer coupling, J′/kB = 3.5 K, a satisfactory description of the magnetic behavior over a wide range of temperature and magnetic field is obtained. The departure of the model curves from the data at the lowest available temperature indicates the presence of additional, weak intra‐ and/or intermolecular interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

A New Spherical Metallacryptate Compound [Na{Cu6(Thr)8(H2O)2(ClO4)4}]·ClO4·5 H2O: Magnetic Properties and DFT Calculations

AbstractThe hexanuclear copper(II) complex with threoninato acid has been synthesized. Its structure can be described as an octahedron cage with D2h symmetry in which six copper ions are bound by eight threoninato acids with a [3.11223130] coordination mode and one Na+ cation being captured within the center of the cage. In contrast with other hexanuclear copper compounds containing amino acids, the title compound has a prolate Cu6 octahedron with the longest axial distance and a rectangle equatorial plane, as well as special coordinated perchlorate ions. Compared with classic cryptate, hexanuclear copper(II) compounds with amino acids can be regarded as a new topologic type of spherical macrotricyclic metallacryptates [2,2,2,2] whose cages have a high selectivity for sodium ions. The analysis of magnetic susceptibility data shows that the threoninato compound has a ground state with spin S = 3. The computing coupling constant between the equatorial Cu centers and the axial ones is 4.4 cm–1,calculated by using DFT methods for a model compound. This is close to three known experimental values of 1.39, 0.56 or 0.43 cm–1 for complexes with 4‐hydroxy‐L‐prolinato, L‐prolinato or L‐threoninato acid as ligands, respectively. The dominant ferromagnetic interactions for these complexes can be essentially attributed to the orthogonality between the magnetic orbitals, dxz or dyz orbitals for the equatorial CuII centers and d orbitals for the axial ones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Structure Study and Luminescence Thermochromism in Hexanuclear 6-Methyl-2-Pyridinethiolato Copper(I) Crystals

The structure of hexanuclear 6-methyl-2-pyridinethiolato copper(I) [Cu6(6-mpyt)(6)] crystals has been studied by the X-ray diffraction analysis. These crystals show highly efficient luminescence whose color changes drastically from red to green-blue with lowering temperature from room temperature (RT) to liquid nitrogen temperature (LNT). This is a new example of luminescence thermochromism for hexanuclear copper(I) cluster compounds. Two relaxed luminescence bands appear predominantly: one (CC-band), red luminescence appearing in the lower-energy region around 1.8 eV at higher temperature, is assigned to the transition between intramolecular orbitals (MO) of a Cu cluster center (CC), and the other (CT-band), green-blue luminescence appearing at the higher energy side of 2.6 eV than the CC-band at lower temperature, is assigned to a charge transfer (CT) transition from the CC-MO to a ligand MO. Additionally, the CT band can be deconvoluted to two subbands CT(L) and CT(H). The intensities of the CC- and the CT-bands change complementarily with temperature via a thermal activation process, giving the thermochromism. All of these band shapes can be fitted by a Gaussian function, and their widths are fairly large obeying the hyperbolic cotangent law. These features reflect our system to be a strong electron-lattice coupling one. The relaxation process of the photoexcited states is discussed in terms of a configuration coordinate model.

Synthesis and characterisation of a hexanuclear copper (I) cluster coordination compound

A novel hexanuclear copper (I) cluster coordination compound has been synthesised by the reaction of N-ethoxy-carbonyl-N'-o-chlorophenylthiourea with cupric chloride in ethanol solution.

Self-assembly of a molecular figure-of-eight strip.

A hexanuclear copper(ii) complex with a figure-of-eight strip topology is formed by metal-directed self-assembly of tritopic ligand L, bis-bidentate glycine hydroxamic acid and Cu(ii) ions in a 2:2:6 ratio.

Ligand substitution in cubic clusters: surprising isolation of the cocrystallization products of Cu8(mu8-Se)[S2P(OEt)2]6 and Cu6[S2P(OEt)2]6.

The cluster (Cu8(mu8-Se)[S2P(OEt)2]6)0.54(Cu6[S2P(OEt)2]6)0.46 (2) was prepared in 78% yield from the reaction of Cu8(Se)[Se2P(OPr)2]6 (1) and NH4S2P(OEt)2 in toluene. The central selenide ion in 2 was characterized by 77Se NMR at delta -976 ppm. The simulated solid-state 31P NMR spectrum shows two components with an intensity ratio close to 55:45. The peak centered at 100.7 ppm is assigned to the 31P nuclei in the hexanuclear copper cluster, and that at 101.1 ppm is due to the octanuclear copper cluster. The single-crystal X-ray diffraction analysis confirms the cocrystallization structures of Cu8(Se)[S2P(OEt)2]6 (54%) and Cu6[S2P(OEt)2]6 (46%) (2: trigonal, space group R3, a=21.0139(13) A, c=11.404(3) A, gamma=120 degrees, Z=3). While the octanuclear copper cluster possesses a 3-fold crystallographic axis which pass through the Cu2, Se, and Cu(2A) atoms, the six copper atoms having the S6 point group symmetry in Cu6[S2P(OEt)2]6 form a compressed octahedron. The Cu8(mu8-Se) cubic core in Cu8(mu8-Se)[S2P(OEt)2]6 is larger in size than the metal core in Cu8(mu8-Se)[Se2P(OPr)2]6 (1) although the bite distance of the Se-containing bridging ligand is larger than that of the S ligand. To understand the nature of the structure contraction of the metal core and metal-mu8-Se interaction, molecular orbital calculations have been carried out at the B3LYP level of density functional theory. MO calculations suggest that Cu-mu8-Se interactions are not very strong and a half bond can be formally assigned to each Cu-mu8-Se bond. Moderate Cu...Cu repulsion exists, and it is the bridging ligands that are responsible for the observed Cu...Cu contacts. Hence, the S-ligating copper clusters have greater Cu...Cu separations because each Cu carries more positive charge in the presence of the more electronegative S-containing ligands.

Hexanuclear copper(II) complex of a novel poly(pyridine) ligand exhibiting unique long distance ferromagnetic interactions through a nitrato-O,O ′ bridge

A novel hexanuclear copper complex [Cu 6(NO 3) 12(opytrizediam) 2(H 2O)][(CH 3) 2CO] 0.5(CH 3CH 2CH 2OH) 0.5 ( 1) with a NO 3 bridge has been synthesized by reaction of Cu(NO 3) 2 · 3H 2O with the new potentially octadentate ligand opytrizediam in n-propanol/acetone solution (opytrizediam= N, N ′-{2,4-di[(di-pyridin-2-yl)amine]-1,3,5-triazine} ethylenediamine). A single-crystal X-ray diffraction analysis showed the presence of six structurally different copper centres. The coordination spheres of four copper(II) ions are best described as square-pyramidal CuN 2O 3 chromophores while the two other copper(II) ions are in a trigonal-bipyramidal CuN 4O environment. Variable-temperature studies on 1 revealed a unique ferromagnetic coupling of two copper(II) ions bridged by a didentate nitrate anion and separated by a distance of 6.391(6) Å, with J=8.6(1) cm −1.

Synthesis, spectroscopy, and solid-state structural characterization of the hexanuclear copper macrocycle [Cu6Cl6(mu-PCHP)6

With an outside diameter of approximately 2 nm, the title complex comprises six copper chloride moities bridged by six 1,3-(CH2PtBu2)2C6H4 ligands (see X-ray crystal structure). The solution properties of the resulting 48-atom macrocycle have been studied by variable-temperature NMR and UV/Vis spectroscopy, as well as by electrochemical studies.