Dinuclear Copper Units Research Articles

Syntheses, Characterization, and X-Ray Crystal Structure of a Co-Crystal Containing One Neutral Mononuclear Copper (II) Unit and One Cationic Dinuclear Copper (II) Unit Assembled with Schiff Base and Perchlorate Copper(II) Salt

The use of 2-{[2-(2-hydroxybenzylideneamino)phenylimino]methyl}phenol (H2L) in metal transition chemistry has yielded a co-crystal which is composed by one neutral mononuclear, one cationic dinuclear and one perchlorate anion. During the formation of the complex, one of the salicylaldimine groups of one of the molecules of the H2L ligand hydrolyzed to form an asymmetrical ligand with an amino group leading to the molecule (2-((2-aminophenylimino)methyl)phenol (HL'). The complex was formulated as {[Cu(L)].[Cu2(L)(L')]}.(ClO4). The structure of the complex was solved by single crystal X-ray crystallography. In the mononuclear unit, the Cu2+ atom is coordinated by one dideprotonated molecule of the ligand acting in tetradentate fashion. In the dinuclear unit, one the Cu2+ atom is coordinated by one dideprotonated molecule of the ligand acting in tetradentate fashion and the other Cu2+ is coordinated by the monodeprotonated (2-((2-aminophenylimino)methyl)phenol (HL') acting in tridentate fashion. The two Cu2+ are bridged by the two phenoxo oxygen atoms of the dideprotonated molecule of the ligand. The complex crystallizes in the triclinic space group Pī with the following parameters: a = 13.8864 (3) Å, b = 14.2078 (4) Å, c = 14.5007 (4)) Å, α = 64.593 (3), β = 71.353 (2), γ = 71.707 (2)°, V = 2395.80 (13) Å3, Z = 2, R1 = 0.037, wR2 = 0.041. The supramolecular structures are consolidated by multiple hydrogen bonds.

Structure and magnetic characterization of tetranuclear closed/double-open cubane core, and 1D polynuclear copper(II) complexes

Three copper(II) complexes namely [Cu4(L1)4]·0.5(H2O) (1), [Cu4(L2)2(HL2)2(H2O)2](sq)·H2O (2) and {[Cu2(L2)2(tp)]·(H2O)}n (3) (H2L1 = [(E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol], H2L2 = [(E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol], sq = squarate and tp = terephthalate ion) have been characterized by structure determination and magnetic analysis. Both 1 and 2 are tetranuclear Cu4O4 species with closed cubane core and double-open cubane like core structure, respectively. On the other hand complex 3 is a 1D polymeric chain, where Schiff base chelated dinuclear copper units are linked through terephthalate ions. C-H…π interactions among the 1D polymeric chains form a 2D supramolecular architecture. Variable temperature magnetic property study indicates overall antiferromagnetic exchange coupling in all complexes.

New polynuclear compounds based on N-benzyliminodipropionic acid: solution studies, synthesis, and X-ray crystal structures

Three new polynuclear compounds based on a dicarboxylic acid ligand are reported. In particular, two Cu(II) coordination compounds, [Cu2(H2O)6(Hbzlidp)2](CF3SO3)2·2H2O (1) and [Cu(NO3)(Hbzlidp)]∞ (2) (bzlidp2− = N-benzyliminodipropionate anion), and a Ni(II) dinuclear compound, [Ni2(H2O)4(bzlidp)2] (3), were synthesized and characterized by IR spectroscopy, elemental analysis and single crystal X-ray diffraction. Different structures were obtained depending on the reaction conditions. The structural analyses reveal that 1 was formed by dinuclear [Cu2(H2O)6(Hbzlidp)2]2+ units built by two copper(II) ions joined through two Hbzlidp− ligands, while 2 was formed by pairs of Cu(II) centers bridged by four syn,syn carboxylate groups to generate “paddle wheel” units. The dinuclear copper units are arranged in a rhombus type grid, in a 2-D layer structure. In both cases, the N was protonated and not coordinated to the metal center. Compound 3 was formed by [Ni2(H2O)4(bzlidp)2] neutral dinuclear units, with octahedral Ni(II) centers. Solution studies of the ligand–M(II) systems (M(II) = Mn, Co, Ni, Cu, Zn, Cd, and Pb) were also carried out.

Supramolecular architectures in Co(II) and Cu(II) complexes with thiophene-2-carboxylate and 2-amino-4,6-dimethoxypyrimidine ligands.

The coordination chemistry of mixed-ligand complexes continues to be an active area of research since these compounds have a wide range of applications. Many coordination polymers and metal-organic framworks are emerging as novel functional materials. Aminopyrimidine and its derivatives are flexible ligands with versatile binding and coordination modes which have been proven to be useful in the construction of organic-inorganic hybrid materials and coordination polymers. Thiophenecarboxylic acid, its derivatives and their complexes exhibit pharmacological properties. Cobalt(II) and copper(II) complexes of thiophenecarboxylate have many biological applications, for example, as antifungal and antitumor agents. Two new cobalt(II) and copper(II) complexes incorporating thiophene-2-carboxylate (2-TPC) and 2-amino-4,6-dimethoxypyrimidine (OMP) ligands have been synthesized and characterized by X-ray diffraction studies, namely (2-amino-4,6-dimethoxypyrimidine-κN)aquachlorido(thiophene-2-carboxylato-κO)cobalt(II) monohydrate, [Co(C5H3O2S)Cl(C6H9N3O2)(H2O)]·H2O, (I), and catena-poly[copper(II)-tetrakis(μ-thiophene-2-carboxylato-κ(2)O:O')-copper(II)-(μ-2-amino-4,6-dimethoxypyrimidine-κ(2)N(1):N(3))], [Cu2(C5H3O2S)4(C6H9N3O2)]n, (II). In (I), the Co(II) ion has a distorted tetrahedral coordination environment involving one O atom from a monodentate 2-TPC ligand, one N atom from an OMP ligand, one chloride ligand and one O atom of a water molecule. An additional water molecule is present in the asymmetric unit. The amino group of the coordinated OMP molecule and the coordinated carboxylate O atom of the 2-TPC ligand form an interligand N-H...O hydrogen bond, generating an S(6) ring motif. The pyrimidine molecules also form a base pair [R2(2)(8) motif] via a pair of N-H...N hydrogen bonds. These interactions, together with O-H...O and O-H...Cl hydrogen bonds and π-π stacking interactions, generate a three-dimensional supramolecular architecture. The one-dimensional coordination polymer (II) contains the classical paddle-wheel [Cu2(CH3COO)4(H2O)2] unit, where each carboxylate group of four 2-TPC ligands bridges two square-pyramidally coordinated Cu(II) ions and the apically coordinated OMP ligands bridge the dinuclear copper units. Each dinuclear copper unit has a crystallographic inversion centre, whereas the bridging OMP ligand has crystallographic twofold symmetry. The one-dimensional polymeric chains self-assemble via N-H...O, π-π and C-H...π interactions, generating a three-dimensional supramolecular architecture.

Antiferromagnetically Coupled Dimeric Dodecacopper Supramolecular Architectures of Macrocyclic Ligands with a Symmetrical μ6-BO3(3-) Central Moiety.

Reactions between 2,6-diformyl-4-alkyl(R)-phenol (R = CH3 or C(CH3)3) and 1,3-diamino-2-hydroxypropane (1,3-DAP) in the presence of copper(II) salts (Cu(BF4)2·6H2O, Cu(ClO4)2·6H2O/H3BO3/Ar) and triethylamine (TEA) in a single pot result in self-assembly of dimeric dodecacopper supramolecular architectures of 30-membered hexatopic macrocyclic ligands (H6L4 and H6L5) with unique and fascinating structures having the BO3(3-) anion as the central species bonded to all six copper centers in a symmetrical fashion (μ6-BO3(3-)). A number of closely related macrocyclic hexacopper complexes are reported: {[Cu6(L4)(μ6-BO3)(μ-H2O)(C3H7NO)2(BF4)][BF4]2·3C3H7NO}2 (1) (DMF = C3H7NO), {[Cu6(L4)(μ6-BO3)(μ-C3H7NO)3][ClO4]3·3C3H7NO}2 (2), {[Cu6(L5)(μ6-BO3)(μ-OH)(H2O)3(C3H7NO)][BF4]2·6C3H7NO·4C2H5OH·2H2O}2 (3), {[Cu6(L5)(μ6-BO3)(μ-CH3OH)(CH3OH)2][ClO4]3·10H2O}2 (4), and {[Cu6(L5)(μ6-BO3)(μ-CH3CO2)(μ-CH3O)(CH3OH)][BF4]·13CH3OH·8H2O}2 (5). A polymeric side product {[Cu2(H2L2)(CH3OH)(BF4)][BF4]}n (6), involving a 2 + 2 macrocyclic ligand, was also isolated and structurally characterized. Complex 6 involves dinuclear copper(II) units linked through BF4(-) anions to form a novel 1D single-chain polymeric coordination compound. This appears to be the first report in which a central BO3(3-) species is linked to six copper(II) ions held together by a single macrocyclic ligand through three μ1,1-O(BO3(3-)) and three μ1,3-O(BO3(3-)) bridges. In complexes 1-5 the BO3(3-) is present in the center of the macrocyclic cavity and is bonded to all six metal centers arranged in a benzene-like hexagonal array. In the hexagonal array there are alternate double (μ-alkoxide and μ1,3-O(BO3(3-))) and (μ-phenoxide and μ1,1-O(BO3(3-))) bridges between the Cu(II) centers. The symmetrical hexa-bridging nature of μ6-BO3(3-) is unprecedented in transition metal complex chemistry, and along with alkoxide and phenoxide bridges in the equatorial plane provides effective pathways for an overall antiferromagnetic exchange interaction between six copper(II) centers. In 1, 3, and 5 the BO3(3-) moiety is produced in one step (synthetic) by an unusual copper(II)-macrocycle complex catalyzed hydrolysis of BF4(-) ion in methanol. In 2 and 4 the central species (BO3(3-)) comes from boric acid (H3BO3) which is added to reaction mixture of Cu(ClO4)2/H6L4/H6L5 under inert conditions to confirm the identity of the central species.

1D Magnetic Interactions in CuII Oxovanadium Phosphates (VPO), Magnetic Susceptibility, DFT, and Single-Crystal EPR

We report the crystal face indexing and molecular spatial orientation, magnetic properties, electron paramagnetic resonance (EPR) spectra, and density functional theory (DFT) calculations of two previously reported oxovanadium phosphates functionalized with Cu(II) complexes, namely, [Cu(bipy)(VO2)(PO4)]n (1) and [{Cu(phen)}2(VO2(H2O)2)(H2PO4)2 (PO4)]n (2), where bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline, obtained by a new synthetic route allowing the growth of single crystals appropriate for the EPR measurements. Compounds 1 and 2 crystallize in the triclinic group P1̅ and in the orthorhombic Pccn group, respectively, containing dinuclear copper units connected by two -O-P-O- bridges in 1 and by a single -O-P-O- bridge in 2, further connected through -O-P-O-V-O- bridges. We emphasize in our work the structural aspects related to the chemical paths that determine the magnetic properties. Magnetic susceptibility data indicate bulk antiferromagnetism for both compounds, allowing to calculate J = -43.0 cm(-1) (dCu-Cu = 5.07 Å; J defined as Hex(i,j) = -J Si·Sj), considering dinuclear units for 1, and J = -1.44 cm(-1) (dCu-Cu = 3.47 Å) using the molecular field approximation for 2. The single-crystal EPR study allows evaluation of the g matrices, which provide a better understanding of the electronic structure. The absence of structure of the EPR spectra arising from the dinuclear character of the compounds allows estimation of weak additional exchange couplings |J'| > 0.3 cm(-1) for 1 (dCu-Cu = 5.54 Å) and a smaller value of |J'| ≥ 0.15 cm(-1) for 2 (dCu-Cu = 6.59 Å). DFT calculations allow evaluating two different exchange couplings for each compound, specifically, J = -36.60 cm(-1) (dCu-Cu = 5.07 Å) and J' = 0.20 cm(-1) (dCu-Cu =5.54 Å) for 1 and J = -1.10 cm(-1) (dCu-Cu =3.47 Å) and J' = 0.01 cm(-1) (dCu-Cu = 6.59 Å) for 2, this last value being in the range of the uncertainties of the calculations. Thus, these values are in good agreement with those provided by magnetic and single-crystal EPR measurements.

Dinuclear copper(II) complexes hold by crab-shaped pincer ligands: Syntheses, structures, luminescent and magnetic properties

Two Cu(II) complexes with N,N′-(2-hydroxy-5-R-1,3-xylylene)bis(N-(carboxymethyl)glycine (R-H5XTA, R=Cl and Br) ligands have been synthesized and their crystal structures have been analyzed by X-ray diffraction methods. The ligands provide a convenient dinucleating feature with the phenolate oxygen providing the bridging function. The complexes consist of dinuclear copper units, hexahydrate copper ion and solvent water molecules. Thereinto, dimer copper ions show two different geometries as Cu1 distorted octahedron and Cu2 square-based pyramid respectively, which has been confirmed by the solid-state electronic absorption spectrum. The thermal decomposition process consists of the loss of corresponding water molecules below 473K and follow-up decomposition of the main structures. Under the excitation of 360nm light, luminescence of ligands is quenched by the coordinated Cu(II) ions and heavy Br atom, respectively. Magnetic study shows that coupling of dinuclear copper ions displays ferromagnetic behavior with the J=+9.03cm−1.

Crystal Structures of Copper-depleted and Copper-bound Fungal Pro-tyrosinase: INSIGHTS INTO ENDOGENOUS CYSTEINE-DEPENDENT COPPER INCORPORATION

Tyrosinase, a dinuclear copper monooxygenase/oxidase, plays a crucial role in the melanin pigment biosynthesis. The structure and functions of tyrosinase have so far been studied extensively, but the post-translational maturation process from the pro-form to the active form has been less explored. In this study, we provide the crystal structures of Aspergillus oryzae full-length pro-tyrosinase in the holo- and the apo-forms at 1.39 and 2.05 Å resolution, respectively, revealing that Phe(513) on the C-terminal domain is accommodated in the substrate-binding site as a substrate analog to protect the dicopper active site from substrate access (proteolytic cleavage of the C-terminal domain or deformation of the C-terminal domain by acid treatment transforms the pro-tyrosinase to the active enzyme (Fujieda, N., Murata, M., Yabuta, S., Ikeda, T., Shimokawa, C., Nakamura, Y., Hata, Y., and Itoh, S. (2012) ChemBioChem. 13, 193-201 and Fujieda, N., Murata, M., Yabuta, S., Ikeda, T., Shimokawa, C., Nakamura, Y., Hata, Yl, and Itoh, S. (2013) J. Biol. Inorg. Chem. 18, 19-26). Detailed crystallographic analysis and structure-based mutational studies have shown that the copper incorporation into the active site is governed by three cysteines as follows: Cys(92), which is covalently bound to His(94) via an unusual thioether linkage in the holo-form, and Cys(522) and Cys(525) of the CXXC motif located on the C-terminal domain. Molecular mechanisms of the maturation processes of fungal tyrosinase involving the accommodation of the dinuclear copper unit, the post-translational His-Cys thioether cross-linkage formation, and the proteolytic C-terminal cleavage to produce the active tyrosinase have been discussed on the basis of the detailed structural information.

Synthesis, characterization and X-ray structural studies of four copper (II) complexes containing dinuclear paddle wheel structures

BackgroundVarious dinuclear copper (II) complexes with octahedral geometry have been reported. The majority of these complexes contain N containing aromatic rings as axial ligands. There are also a few cases where the solvent used in the reaction occupies the axial position of the dinuclear copper (II) complex. This may occur by planned synthesis or some times by serendipity. Here we report some four copper (II) complexes containing solvent and or N containing heterocyclic ring as the axial ligand.ResultsFour compounds, each containing dinuclear Copper (II) units (with the most robust, frequently occurring paddle wheel structures) were synthesized and characterised by single crystal X-ray diffraction and by IR spectroscopy. The compounds 1 & 2 have the general formula Cu2(RCOO) 4(L)2 [(for (1) RCOO= 4-Chloro Benzoate, L= Isopropanol; for 2 RCOO= Benzoate, L= 2-Amino-4,6-dimethyl pyrimidine )] while 3 & 4 have the general formula, Cu2(RCOO) 4(S)2 Cu2(RCOO) 4(L)2 [RCOO=5-Chloro-thiophene-2-carboxylate L= 2-Amino-4,6-dimethyl pyrimidine, for 3 S= ethanol; for 4 S= methanol ]. A wide range of hydrogen bonds (of the O-H…O, N-H…O and N-H…N type) and π-π stacking interactions are present in the crystal structures.ConclusionsAll compounds contain the dinuclear units, in which two Cu (II) ions are bridged by four syn, syn-η1:η1:μ carboxylates, showing a paddle-wheel cage type with a distorted octahedral geometry. The compounds 1 &2 contain a single dimeric unit while 3 &4 contain two dimeric units. The structures 3 and 4 are very interesting co-crystals of two paddle wheel molecules. Also it is interesting to note that the compounds 3 &4 are isostructural with similar cell parameters. Both the compounds 3 &4 differ in the solvent molecule coordinated to copper in one of the dimeric units. In all the four compounds, each of the copper dimers has an inversion centre. Every copper has a distorted octahedral centre, formed by four oxygen atoms (from different carboxylate) in the equatorial sites. The two axial positions are occupied by copper and the corresponding ligand.

Synthesis, structure and magnetic properties of phosphate-bridged polynuclear copper(II) complexes

Three new phosphate-bridged copper(II) complexes, [Cu4(H2O)2(phen)4(μ4-PO4)2(μ2-O)]·11H2O (1), [Cu4(bpy)4(μ4-PO4)2(μ2-Cl)2]·18H2O (2) and [Cu2(bpp)4(H2PO4)2](HPO4)·H2O (3) (phen=1,10-phenanthroline, bpy=2,2-bipydine and bpp=1,3-bis(4-pyridyl)-propane), have been synthesized under ambient conditions. The tetranuclear Cu(II) butterfly cores in 1 are aggregated to 2D supramolecular layer via intermolecular π–π stacking interactions. In 2, the dinuclear copper units are bridged by the phosphate and Cl− anion to generate centrosymmetric tetranuclear complex molecules [Cu4(bpy)4(μ4-PO4)2(μ2-Cl)2], which are aggregated to 2D layers via π–π stacking interactions. The Cu atoms in 3 are interlinked by a pair of bpp ligands to generate 2D (4,4) network which is through twofold ‘2D parallel/2D parallel’ mode inclined interpenetration to induce 3D motifs. The variable temperature magnetic characterizations suggest antiferromagnetic coupling interactions with J=−9.38 and −28.03cm−1 for 1, J=−2.41cm−1 for 2, respectively.

Tripodal bis(imidazole)-based ligands and their chelation to copper(ii)

Three new copper(II) compounds are described containing chelating bis(imidazole)-based ligands. Compound 1, [Cu2(L1)2(H2O)2][SiF6]2·10H2O, was obtained by reaction of [bis-(1H-imidazol-2-yl)-methyl]-pyridin-2-ylmethyl-amine (L1) with Cu(BF4)2·6H2O in a glass vessel for a few weeks. The single-crystal X-ray structure of 1 consists of dinuclear copper(II) units, formed through ligand sharing. The starting BF4− anion was replaced by the SiF62− in the crystal structure of 1. In the crystal lattice, a discrete (H2O)8 cluster forms an eight-membered ring and is linked through four shared water molecules with the other (H2O)8 cluster. Both water clusters show hydrogen-bonding interactions with the neighbouring SiF62− anion. To investigate the effect of the presence of a bridging ligand such as oxalate on the coordination chemistry of L1 and copper(II) ion, compound 2, [Cu2(L1)(H2O)2][Cu(C2O4)2(ClO4)2]·2H2O, was prepared by reaction of L1 and Cu(ClO4)2·6H2O in the presence of oxalic acid; the crystal structure is built from 4+ and 4− ions in the crystal lattice. Compound 3, [Cu(ClO4)(C2O4)(HL2)H2O]·2H2O, was formed from the reaction of ligand [bis-(1H-imidazol-2-yl)-methyl]-isopropyl-amine (L2) and Cu(ClO4)2·6H2O in the presence of oxalic acid. The isopropylamine group is not coordinated to the copper in this case, but protonated. In compound 3, a mononuclear copper(II) unit is present, built from a bidentate L2, a bidentate oxalate, a monodentate perchlorate and a water. Two copper coordination entities are doubly bridged through hydrogen bonds with twice the pathway [Cu–OC2O4–(Owater)–Cu] to form a dimeric-like species. Low-temperature magnetic susceptibility studies showed no interaction between copper(II) ions.

Synthesis, structure, magnetism and theoretical study of a series of complexes with a decanuclear core [Ln(iii)2Cu(ii)8] (Ln = Y, Gd, Tb, Dy)

A family of four isomorph complexes with a decanuclear [Cu8Ln2] core of general formula [Ln2Cu8(μ-PyO)12(μ4-O)2(μ-Cl)2Cl4(H2O)2]·nH2O [Ln(III) = Y(III) (1), Gd(III) (2), Tb(III) (3), Dy(III) (4); 2-PyOH = 2-hydroxypyridine] was isolated and structurally characterized. All compounds are isomorphs and may be viewed as a hexanuclear central core sandwiched in between two lateral dinuclear copper units. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization were investigated on polycrystalline samples. The yttrium compound 1 showed an overall behavior dominated by an antiferromagnetic interaction between the copper ions, while for compounds 2–4 the magnetic behavior indicated the addition of a ferromagnetic interaction with the lanthanide ions. The magnetic properties were computationally studied by means of fragment ab initio calculations. The calculation on the yttrium complex allowed determining the strength and sign of the Cu⋯Cu magnetic interactions considering three antiferromagnetic coupling constants: two within the central (J3 = −44 cm−1) and the lateral (J4 = −40 cm−1) copper dinuclear unit, and one (J5 = −24 cm−1) between the lateral and the central copper. Simulation of the magnetic behavior of the Dy (4) compound gave J1 = +0.25 cm−1 for Dy–Dy and J2 = +2.0 cm−1 for Dy–Cu pairs. The calculated g tensors of the copper(II) ions were found to be quite anisotropic and contributed via anisotropic exchange interactions, together with zero-field (crystal field) splitting on Ln, to the weak single-molecule magnet (SMM) behavior of 2, 3 and 4. Among them, the highest coercivity was found in the gadolinium complex (2), despite the fact that it is much less anisotropic than the other two. We explain this surprising result by a higher multiplicity of the ground spin term in 2 compared to the ground manifolds of states in 3 and 4. Besides, due to relatively large Cu–Gd interaction, the ground exchange term in 2 has enough separation from excited exchange terms, which makes the barrier of reversal of magnetization efficient in this complex.

Ferromagnetic Spin Ladder System: Stack of Chlorido‐Bridged Dinuclear Copper(II) Complexes with 2‐Methylisothiazol‐3(2H)‐one

AbstractA dinuclear copper(II) complex, [{CuIICl(O‐mi)}2(μ‐Cl)2] [mi = 2‐methylisothiazol‐3(2H)‐one], has been synthesized and its molecular structure in the solid state determined by single‐crystal X‐ray analysis. The crystal consists of centrosymmetric dinuclear copper(II) units in which each copper(II) ion is doubly bridged by two chloride ions and has a slightly distorted square‐planar geometry with a terminal chlorido ligand and a terminal mi ligand coordinated through the oxygen atom. The dinuclear units stack one on top of another to form a one‐dimensional two‐leg ladder structure. The magnetic susceptibility of the powder was measured in the temperature range 3.0–302 K. It was found that there are ferromagnetic interactions along the rung (in the same direction of the intramolecule; Jrung = +5.03 ± 0.03 cm–1) and the leg (in the same direction of the intermolecule; Jleg = +1.96 ± 0.02 cm–1) and an antiferromagnetic interaction along the diagonal (Jx = –1.36 ± 0.02 cm–1), the experimental data being fitted by the numerical calculation for a twelve‐site ladder Hamiltonian. In addition, DFT calculations with the UB3LYP functional on the model complex [{CuIICl(O‐mi)}2(μ‐Cl)2] gave an intramolecular magnetic coupling constant J = +28.6 cm–1 and indicated that the spin‐density distribution on O in mi is less than that on the terminal Cl. We conclude that the O‐donor ligand at the terminal position plays an essential role in the emerging intramolecular ferromagnetic interaction.

Synthesis, structure, cytotoxic activities and DNA-binding properties of tetracopper(II) complexes with dissymmetrical N,N′-bis(substituted)oxamides as ligands

To compare the cytotoxicities and the DNA-binding properties in tetranuclear complexes with different bridging ligands, two tetracopper(II) complexes with formulae of [Cu4(oxbe)2Cl2(bpy)2]·4H2O (1) and [Cu4(oxbm)2Cl2(bpy)2]·2H2O (2) were synthesized, where H3oxbe and H3oxbm stand for N-benzoato-N′-(2-aminoethyl)oxamide and N-benzoato-N′-(1,2-propanediamine)oxamide, respectively, and bpy is 2,2′-bipyridine. Complex 1 was characterized by elemental analyses, IR and electronic spectra and single-crystal X-ray diffraction. The crystal structure reveals the presence of the circular tetranuclear copper(II) cations which are assembled by a pair of cis-oxamido-bridged dinuclear copper(II) units through carboxyl bridges. The crystal structure of complex 2 has been reported in our previous paper. However, the bioactivities were not studied. Cytotoxicities experiments reveal that both the two complexes exhibit cytotoxic effects against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549, and complex 1 has the better activities than those of complex 2. The results of the interactions between the two complexes and herring sperm DNA (HS-DNA) suggest that the two complexes interact with HS-DNA in the mode of intercalation with the intrinsic binding constants of 3.93×104M−1 (1) and 2.48×104M−1 (2). These results indicated that the bridging ligands may play an important role in the cytotoxicities and the DNA-binding properties of tetranuclear complexes.

Structural diversity, photoluminescence and magnet properties of complexes based on a V-shaped polycarboxylate

The self-assembly of a V-shaped ligand 3,3′,4,4′-diphenylsulfonetetracarboxylate (dstc) and metal salts in the presence of a series of N-donor ligands yielded four new complexes, namely, [Cu4(H2dstc)4(phen)4]·12H2O (1), {[Cu2(dstc)(bpe)(H2O)2]·4H2O}n (2), [Cu3(dstc)(bipy)(μ2-OH)2(H2O)2]n (3), {[Cd5(dstc)2(bipy)2(μ3-OH)2(H2O)4]·4H2O}n (4) (phen=1,10-phenanthroline; bpe=1,2-bis(4-pyridyl)ethene; bipy=4,4′-bipyridine). All the complexes were structurally determined by single-crystal X-ray diffraction and characterized by elemental analyses, IR spectra, X-ray powder diffraction and TG analyses. Complex 1 is a discrete tetranuclear unit, which further assembles into a 3D supramolecular framework by intermolecular hydrogen bonding interactions. Complex 2 is composed of 2D 44 grid-like layers based on dinuclear copper units. Complex 3 features a rare 3D (6,8)-connected topological net consisting of trimetallic clusters. 12-connected pentanuclear cadmium clusters are observed in complex 4 and the resulting structure shows an uncommon (4,12)-connected topology. The structural differences among 1–4 demonstrate that the nature of the N-donor assistant ligands and metal ions can play critical roles in the formation and structures of the resulting complexes. Magnetic studies showed antiferromagnetic interactions for 1 and 3. In addition, the luminescent property of 4 was also studied.

Synthesis, structure, and DNA-binding studies of a new tetracopper(II) complex bridged by dissymmetrical N-benzoato-N′-(2-aminoethyl)oxamide

A new oxamido-bridged tetracopper(II) complex, [Cu4(oxbe)2(bpy)2](ClO4)2 · 2H2O, where H3oxbe and bpy stand for N-benzoato-N′-(2-aminoethyl)oxamide and 2,2′-bipyridine, has been synthesized and characterized by elemental analyses, molar conductivity, infrared and electronic spectra, and single-crystal X-ray diffraction. It crystallizes in triclinic system, space group P-1, with crystallographic data: a = 7.829(5) Å, b = 12.680(5) Å, c = 13.420(5) Å, α = 104.665(5)°, β = 95.275(5)°, γ = 106.931(5)°, and Z = 1. The circular tetranuclear copper(II) cation [Cu4(oxbe)2(bpy)2]2+ with an embedded center of inversion is assembled by a pair of cis-oxbe-bridged dinuclear copper(II) units through coordination between carboxyl and copper(II). One copper(II) is located in a slightly distorted square-planar environment, while the other is in a distorted square-pyramidal geometry. In the crystal structure, abundant hydrogen bonds and aromatic stackings link the tetranuclear copper(II) units into an overall 3-D framework. Interactions of the tetranuclear copper(II) complex with herring sperm DNA (HS-DNA) are investigated by using UV absorption and fluorescence spectra, electrochemical techniques, and viscometry. The results suggest that the tetranuclear copper(II) complex interacts with DNA by intercalation with an intrinsic binding constant of 1.47 × 105 mol−1 L.

Magnetic and Conducting Properties of New Halide-Bridged Mixed-Valence CuI−CuII 1D Coordination Polymers Including a Hexamethylene Dithiocarbamate Ligand

New mixed-valence Cu(I)-Cu(II) coordination polymers with one-dimensional, infinite-chain structures, [Cu(I)(2)Cu(II)X(2)(Hm-dtc)(2)(CH(3)CN)(2)](n) [Hm-dtc(-) = hexamethylene dithiocarbamate; X = Br(-) (1), I(-) (2)], have been prepared and structurally characterized by X-ray diffraction. These complexes consist of a mononuclear copper(II) unit Cu(II)(Hm-dtc)(2) and dinuclear copper(I) units Cu(I)(2)(CH(3)CN)(2)X(2). Magnetic studies have revealed that these complexes have a relatively strong antiferromagnetic interaction [J = -26.9 cm(-1) (1) and J = -22.2 cm(-1) (2)] between the unpaired electrons of the Cu(II) ions through the dinuclear copper(I) halide unit of Cu(I)(2)X(2) in the chain. The electrical properties of 1 and 2 are investigated using an impedance spectroscopy technique, and it is revealed that these complexes exhibit intriguing semiconducting properties with small activation energies [E(a) = 0.562 eV (1) and E(a) = 0.479 eV (2)].

Copper(II) succinate complexes with 1,2-di-4-pyridylethane and 1,3-di-4-pyridylpropane

The compounds poly[di-mu(4)-succinato-mu(2)-1,2-di-4-pyridylethane-dicopper(II)], [Cu(2)(C(4)H(4)O(4))(2)(C(12)H(12)N(2))](n), (I), and poly[di-mu(4)-succinato-mu(2)-1,3-di-4-pyridylpropane-dicopper(II)], [Cu(2)(C(4)H(4)O(4))(2)(C(13)H(14)N(2))](n), (II), exhibit polymeric structures with the dicopper units doubly bridged by bis-bidentate succinate groups and crosslinked by the separator bis(pyridyl) molecules. In (I), the molecule exhibits a centre of inversion located midway between the core Cu-dimer atoms and another that relates half of the bis(pyridyl)ethane ligand to the other half. Compound (II) has a similar molecular packing but with a doubled lattice constant and noncentrosymmetric core units. An antiferromagnetic interaction due to the dinuclear copper units was deduced from magnetic subsceptibility measurements, and spin triplet signals were detected in the electron paramagnetic resonance spectra for both compounds.

Supramolecular Architectures and Magnetic Properties of Self‐Assembled Windmill‐Like Dinuclear Copper(II) Complexes with Purine Ligands

AbstractThree new CuII compounds, [Cu2(μ‐ade)4(H2O)2]·(bpa)·8H2O (1), [Cu2(μ‐Hade)4(H2O)2](NO3)4·2[Cu(pic)2(H2O)]·6H2O (2) and [Cu2(μ‐6Clpur)4(H2O)2]·~6H2O (3) [in which ade = adeninate anion, Hade = 7H‐adenine, 6Clpur = 6‐chloropurinate anion, bpa = 1,2‐bis(4‐pyridyl)ethane, pic = 2‐pyridinecarboxylate anion], are reported. Their crystal structures consist of dinuclear copper(II) units, in which four ligands arranged in a windmill‐like fashion bridge the metal ions through a nonlinear NCN group. Supramolecular crystal building of compound 1 is essentially maintained by an extensive network of hydrogen‐bonding interactions that involves direct contacts between the nucleobases. In contrast, in compound 2 there is no evidence for direct interactions between the nucleobases, but the hydrogen bonds among the nucleobases and nitrate counteranions are especially relevant. Compound 3 is mainly built up from T‐shaped noncovalent Cl···N interactions and hydrogen‐bonding interactions involving the crystallization solvent molecules. Magnetic susceptibility measurements indicate the presence of strong intradimeric antiferromagnetic interactions with large singlet–triplet splittings of –222 (for 1), –288 (for 2) and –255 (for 3) cm–1. DFT calculations were carried out to evaluate the dependence of the magnetic coupling value as a function of some key structural parameters: the Cu–N basal plane distance, the axial Cu–Ow distance and the Cu···Cu distance. DFT calculations also revealed that the nature of the bridging ligand is a crucial factor. In this way, the strength to transmit the magnetic interaction of the different bridging ligands is explained on the basis of the number of electron lone pairs.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

In situ synthesis and crystal growth of copper(I) carbonyl trifluoroacetate: a dinuclear [Cu2(O2CCF3)2(CO)2] core structure confirmed

Abstract The solid state structure of the long known but inadequately characterized compound, namely the mixed ligand copper(I) carbonyl trifluoroacetate, [Cu2(O2CCF3)2(CO)2] (1), has been determined by single crystal X-ray crystallography. Instead of the previously assigned tetranuclear core structure, its main building block is now confirmed to be a dinuclear copper(I) unit that is cis-bridged by two trifluoroacetate ligands. The Cu · · · Cu separation within the unit is 3.1382(6) Å. Additionally, each copper center has one terminally bound carbonyl with a Cu–C distance of 1.806(3) Å. In the solid state, 1 displays a 1D chain structure comprised of the [Cu2(μ 2-O2CCF3)2(CO)2] units held by axial Cu · · · O interactions at 2.2181(13) Å.