Polynuclear Copper Research Articles

Exploring the synthesis, structure and properties of two phenoxy-bridged polynuclear Cu(II) and Ni(II) complexes containing salamo-based bicompartmental ligand

A salamo-based bicompartmental ligand H4L was successfully prepared, which self-assembled with copper(II) and nickel(II) salts in stoichiometric ratios of 1:2 to construct polynuclear copper(II) and nickel(II) complexes: [Cu2(HL)(NO3)(H2O)] (1) and [Ni4(μ-HL)2(μ-OAc)2]⋅2CH3COCH3 (2). Complex 1 contains one partially deprotonated (HL)3− part, two copper(II) atoms, one coordinated monodentate nitrate ion and one coordinated water molecule. Each copper(II) center is located in the geometric structure of square pyramidal. While complex 2 is composed of four nickel(II) atoms, two ligand (HL)3− parts, and two bridging μ-OAc− anions. The differently structural complexes acquired may be attributed to the different solvents and anions used in the synthesis process. Whether or not 3-hydroxyl group of salicylaldehyde unit in H4L is involved in the coordination further influences the diversification of the structures of the complexes. The reaction sites and intermolecular interactions were further evaluated by MEPs, IRI, Hirshfeld surface and finally the fluorescence properties were explored.

Comparative analysis of EPR parameters in X-, Q-, W-bands for exchange-coupled copper(II) dimers

In this work, binuclear, polymeric binuclear, and molecular 16-nuclear copper(II) complexes [Py2Cu2(Piv)4] (1), {[(EtOH)2Cu2(Chda)2]·EtOH}n (2) and [K2(H2O)6(Py)8Cu16(OH)2(Chda)16]·EtOH·MeCN·3H2O (3) (piv is pivalate, Chda is 1,1-cyclohexanediacetate) have been studied by EPR spectroscopy in the X-, Q- and W-bands. Polynuclear copper(II) complexes are formed by binuclear fragments bonded by bridging carboxylate anions. In compounds 1–3, only pairwise interactions between copper ions are observed, despite the fact that in 2 and 3 there may be additional interactions between copper ions belonging to different dimers.

Emission and Luminescent Vapochromism Control of Octahedral Cu4 I4 Complexes by Conformationally Restricted P,N Ligands.

A conformationally restricted P,N-ligand capable of the design of polynuclear copper(I) complexes was synthesized via the reaction of primary pyridylphosphine, paraformaldehyde, and benzhydrylamine. The reaction of the ligand with copper(I) iodide leads to the tetranuclear copper(I) complex with the octahedral type of copper-iodide core. Different orientation of coordination bonds of the ligands relative to the P,N2 -heterocyclic fragments and to the Cu4 I4 cores leads to the existence of two types of conformers of the complex with "compact" or "stretched" geometry of the Cu4 I4 cluster. This lability of the complex allowed for obtaining two crystalline phases displaying green or red luminescence. The TDDFT computations along with XRD structural analysis gave a strong interpretation of the green emission belonging to the "compact" form of the complex and belonging of the red emission to the "stretched" form. Moreover, both crystalline phases demonstrate the strong vapochromic responses of luminescence on the vapors of wide range of solvents.

SYNTHESES AND CRYSTAL STRUCTURES OF COPPER(II) AND ZINC(II) COMPLEXES DERIVED FROM 5-BROMO-2-((CYCLOPROPYLIMINO)METHYL)PHENOL WITH ANTIBACTERIAL ACTIVITY

Four new complexes of copper(II) and zinc(II), [Cu2L4] (1), [Cu2L2(N(CN)2)2]n (2), [Zn(HL)2I2] (3) and [Zn(HL)2(NCS)2] (4), where L is 5-bromo-2-((cyclopropylimino)methyl)phenolate, HL is the zwitterionic form of 5-bromo-2-((cyclopropylimino)methyl)phenol, were synthesized and characterized by elemental analysis and IR and UV-Vis spectroscopy. Structures of the complexes were further confirmed by single crystal X-ray structure determination. Complex 1 is a phenolate bridged dinuclear copper(II) compound, with the Cu atom in square pyramidal coordination. Complex 2 is a phenolate and dicyanamide bridged polynuclear copper(II) compound, with the Cu atom in square pyramidal coordination. Complexes 3 and 4 are mononuclear zinc(II) compounds, with the Zn atoms in tetrahedral coordination. The compounds were assayed for their antimicrobial activities. Complexes 1 and 2 have the most activities on B. subtilis, with MIC values of 1.2 μg mL–1.

Solvent-dependent formation of 1D coordination polymers based on polynuclear copper(II)-carboxylate fragments and 4-(pyridine-3-yl)methyleneamino-1,2,4-triazole linkers

The solvent used for the synthesis and crystallization was shown to affect the composition and structure of compounds formed in the reaction of copper(II) trimethylacetate with a Schiff base, 4-(pyridin-3-yl)methyleneamino-1,2,4-triazole (L). The reaction of [Cu2(piv)4(Hpiv)2] (Hpiv – trimethylacetic acid) in MeCN was found to give the crystals of 1D coordination polymer {[Cu2(piv)4(L)]·MeCN}n (1), the structure of which contains binuclear {Cu2(piv)4} units linked by the bridging organic ligand L. A similar reaction in MeOH or EtOH gave 1D coordination polymers {[Cu6(OH)2(piv)10(L)2(ROH)2]∙4ROH}n (2: R = Me, 3: R = Et) whose structure is composed of alternating binuclear {Cu2(piv)4} and tetranuclear {Cu4(OH)2(piv)6(L)2(ROH)2} units bound by N-donor ligand L. Storage of the mother liquor obtained after the isolation of the crystals of 3 leads to the crystallization of chained polymer [Cu(piv)2L]n (4). The structures of new complexes 1–4 were determined by single crystal X-ray diffraction. According to magnetochemical measurements for 1 and 3, antiferromagnetic exchange interactions are observed in these compounds between CuII ions (S = ½) in binuclear {Cu2(piv)4} units (J = −190.5 and −215 cm−1, respectively), as well as dominate in tetranuclear {Cu4(OH)2(piv)6(L)2(EtOH)2} units of 3 (J1 = −202 cm−1, J2 = –23 cm−1, J3 = 18 cm−1).

Syntheses, Characterization and Crystal Structures of Dicyanamide Bridged Polynuclear Copper(II) and Zinc(II) Complexes with Urease Inhibitory Activity.

A pair of structurally similar dicyanamide bridged copper(II) and zinc(II) complexes [CuL(dca)]n (1) and [ZnL(dca)]n (2), were prepared from the fluorine containing Schiff base 5-fluoro-2-(((2-hydroxyethyl)imino)methyl)phenol (HL). The compounds were characterized by physico-chemical methods. Structures of the complexes were confirmed by single crystal X-ray diffraction. The Cu atom in complex 1 is in square pyramidal coordination, whereas the Zn atom in complex 2 is in trigonal bipyramidal coordination. The copper complex has effective Jack bean urease inhibitory activity, with IC50 value of 0.14±0.12 μmol L-1.

Crystalline phase transitions and water-soluble complexes of copper(I) 2-hydroxyethanethiolate

The coordination polymer copper(I) 2-hydroxyethanethiolate, (CuSCH2CH2OH)n, though insoluble in all common solvents, dissolved readily in basic aqueous solutions of the thiolate anion (HOCH2CH2S–) of 2-mercaptoethanol to form a single species: the tetranuclear cluster [Cu4(µ-SCH2CH2OH)6]2–. From this solution were grown X-ray quality single crystals of copper(I) 2-hydroxyethanethiolate. This compound underwent a hitherto unknown crystal phase transition at ca. 6 °C, from point group P212121 to Pna21, with noticeable changes in the geometry of the Cu-S layer and in the orientation of the alkylthiolate side chains. When the bulky base tetrabutylammonium hydroxide was employed in the aqueous thiolate solution used to dissolve (CuSCH2CH2OH)n, the water-soluble polynuclear copper(I) complex bis(tetrabutylammonium) hexakis(µ-2-hydroxyethanethiolato) tetracuprate(I), [(C4H9)4N]2[Cu4(µ-SCH2CH2OH)6], could be isolated as X-ray quality crystals. Structural characterization of this complex revealed a tetrahedral arrangement of copper(I) centers with thiolates bridging the edges of the tetrahedra. On standing, this complex degraded to a larger polynuclear Cu(I) sulfide cluster.

Solvent-induced synthesis and crystal structures of copper(II) complexes derived from 4-chloro-2-[(2-hydroxymethylphenylimino)methyl]phenol with antibacterial activity

Two new polynuclear copper(II) complexes, [Cu2L2] (1) and [Cu4L4]CH2Cl2 (2), where L is 4-chloro-2-[(2-hydroxymethylphenylimino)methyl]phenolate, were synthesized and characterized by IR and UV–Vis spectroscopy. The molecular structures of the complexes were confirmed by single-crystal X-ray determination. The Cu ions in dinuclear complex 1 are in square planar coordination, while those in tetranuclear complex 2 are in square pyramidal coordination. The solvents used in the synthesis and crystallization play an important role for the formation of the final structures of the complexes. The Schiff base and two copper complexes were assayed for antibacterial activities by the MTT method.

Interplay of the intermolecular and intramolecular interactions in stabilizing the thione-based copper(I) complexes and their significance in protecting the biomolecules against metal-mediated oxidative damage

The synthesis, characterization, and X-ray structure of a series of mono, tri, and polynuclear copper complexes of benzimidazole-based N-substituted thiones, BzMeSH (10) and BzOHSH (11), and N,N'-disubstituted, BzMeSMe (12) and BzOHSMe (13) are reported here. The X-ray structure analyses of the copper-thione complexes have revealed that the coordination behaviour and the geometry of the central metal ion in these complexes are significantly dependent on the type of the counter anion used in the reaction. For instance, the reactions of benzimidazole-based thiones with CuCl2 afforded mononuclear trigonal planar Cu(I) complexes 14, 15, 18, and 19. On contrast, upon reaction with CuSO4, 10 afforded the trinuclear copper complex 16, in which thione 10 acts as a bridging as well as terminal ligand, leading to the formation of a six-membered Cu3S3 cluster. The chair-form of six-membered Cu3S3 ring is further stabilized by six intramolecular H-bonding interactions, with overall stabilization energy of 19.28 kcal.mol−1, between the free NH group of 10 and O atom of the counter anion SO42–. Whereas, when thione 10 was reacted with CuI, a 1D-polymeric chain-like copper complex 17 was obtained as a thermodynamically stable product, in which both 10 and iodine act as bridging ligand. The 3D network of complexes has revealed that these copper-thione compounds are stabilized by the presence of various types of intermolecular and intramolecular H-bonding and π − π stacking interactions in the solid state. NBO analysis of the crystal geometries revealed that the strength of these interactions ranging from 0.14 to 5.67 kcal.mol−1. We have also demonstrated that the N-substituted thiones have excellent reactive oxygen species (ROS) scavenging property and, thus, protect biomolecules including DNA and protein against Cu(I)-mediated oxidative damage.

The Influence of Aryl Substituents on the Supramolecular Structures and Photoluminescence of Cyclic Trinuclear Pyrazolato Copper(I) Complexes.

Cyclic trinuclear complexes with group 11 metal(I) ions are fascinating and important to coordination chemistry. One of the ligands known to form these cyclic trinuclear complexes is pyrazolate, which is a bridging ligand that coordinates many transition metal ions in a Npz–M–Npz linear mode (Npz = pyrazolyl nitrogen atom). In these group 11 metal(I) ions, copper is the most abundant metal. Therefore, polynuclear copper(I) complexes are very important in this field. The cyclic trinuclear copper(I) complex [Cu(3,5-Ph2pz)]3 (3,5-Ph2pz– = 3,5-diphenyl-1-pyrazolate anion) was reported in 1988 as a landmark complex, but its photoluminescence properties have hitherto not been described. In this study, we report the photoluminescence and two different polymorphs of [Cu(3,5-Ph2pz)]3 and its derivative [Cu(3-Me-5-Phpz)]3 (3-Me-5-Phpz– = 3-metyl-5-phenyl-1-pyrazale anion). The substituents in [Cu(3-Me-5-Phpz)]3 cause smaller distortions in the solid-state structure and a red-shift in photoluminescence due to the presence of intermolecular cuprophilic interactions.

New mono- and polynuclear copper(II) complexes: Structural characterization, quantum chemical calculations and antioxidant superoxide dismutase studies

Two copper(II) complexes have been synthesized and characterized using elemental and spectral analysis. The molecular structures of both complexes have been confirmed by single crystal X-ray analysis. The stability of the metal centre was examined using cyclic and differential pulse voltammetry in DMSO solution. X-band electron paramagnetic spectra were recorded both in solid and frozen solution to confirm the d 9 configuration. Frozen solution spectra of complexes have the trend in the spin Hamiltonian parameters and cm -1 revealing a ground state with tetragonal symmetry for copper(II) ion. Density functional calculations have been performed and results are found to agree with the experimental results. Antibacterial activities of complexes were screened by taking gram-positive and gram-negative bacteria. Further, in vitro antioxidant (superoxide dismutase) properties of 1 and 2 showed considerable activity compared to other SOD mimics.

Syntheses, Crystal Structures, and Antimicrobial Activities of Copper(II) Complexes Derived from N,N'-Bis(5-Fluorosalicylidene)-1,3-Propanediamine

Two new Schiff base copper(II) complexes, [Cu2L2] (I) and [Cu2L(NCNCN)2]n (II), where L is the dianionic form of N,N'-bis(5-fluorosalicylidene)-1,3-propanediamine (H2L), were synthesized and characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal X-ray determinations (CIF files CCDC. nos. 2000415 (I) and 2000416 (II)). Complex I is a phenolate bridged dinuclear copper(II) compound. Complex II is a phenolate and dicyanoamide bridged polynuclear copper(II) compound. In both complexes, the Cu atoms are in square pyramidal coordination. The Schiff base ligand coordinates to the Cu atoms through the phenolate O and imino N atoms. The Schiff base H2L and the two complexes showed high selectivity and antimicrobial activities against a number of the bacteria and fungi.

Tethered Polynuclear Copper–Chalcogenolate Assemblies Enabled via NHC Ligation

The polynuclear copper–chalcogenolate complexes, 1,1′-fc[CH2ECu(IPr)]2 (E = S (1), E = Se (2); fc = ferrocenyl; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), [1,4-{CH2ECu(IPr)}2C6Me4] (E...

Diverse Surface Chemistry of Cobalt Ferrite Nanoparticles to Optimize Copper(II) Removal from Aqueous Media.

Water pollution by heavy metals is one of the most serious worldwide environmental issues. With a focus on copper(II) ions and copper complex removal, in the present study, ultra-small primary CoFe2O4 magnetic nanoparticles (MNPs) coated with octadecylamine (ODA) of adequate magnetization were solvothermally prepared. The surface modification of the initial MNPs was adapted via three different chemical approaches based on amine and/or carboxylate functional groups: (i) the deposition of polyethylimide (PEI), (ii) covalent binding with diethylenetriaminepentaacetic acid (DTPA), and (iii) conjugation with both PEI and DTPA, respectively. FT-IR, TGA, and DLS measurements confirmed that PEI or/and DTPA were successfully functionalized. The percentage of the free amine (−NH2) groups was also estimated. Increased magnetization values were found in case of PEI and DTPA-modified MNPs that stemmed from the adsorbed amine or oxygen ligands. Comparative UV–Vis studies for copper(II) ion removal from aqueous solutions were conducted, and the effect of time on the adsorption capacity was analyzed. The PEI-modified particles exhibited the highest adsorption capacity (164.2 mg/g) for copper(II) ions and followed the pseudo-second-order kinetics, while the polynuclear copper(II) complex Cux(DTPA)y was also able to be immobilized. The nanoadsorbents were quickly isolated from the solution by magnetic separation and regenerated easily by acidic treatment.

Synthesis of the first chiral polynuclear copper(i) complex based on (R)-1-(1-phenyl)ethyl-3-(O,O-diethylthiophosphoryl)thiourea and its characterization in the solid state and solution

The reaction of chiral N-thiophosphorylated thiourea with Cu(ii) acetate is accompanied by copper reduction and leads to the formation of a polynuclear complex with the core composed of six Cu(i) ions alternating with sulfur atoms.

Construction of polynuclear copper(II) complexes from mono- and binuclear modules

Construction of polynuclear copper(II) complexes from mono- and binuclear modules

Mono- and poly-nuclear copper(II) carboxylates with flourous ligands: Synthesis, structure and improved properties

Polynuclear copper(II) complexes [Cu(para-fluorophenyl acetate)2]n (1) and [Cu(para-nitrophenyl acetate)2]n (2) were converted in-situ to mono-nuclear complexes [Cu(para-fluorophenyl acetate)2(1,10-Phenanthroline)(H2O)] (3) and [Cu(para-nitrophenyl acetate)2(2,2́-Bipyridine)(H2O)].3H2O (4). The complexes were isolated in quantitative yield, purified and characterized using FT-IR, absorption, electrochemical, electron paramagnetic resonance and powder XRD techniques yielding results in accordance with structural data. Structures of 1 and 2 consist of directly interlinked paddlewheel units with square pyramidal geometry while those of 3 and 4 are mononuclear with octahedral and square pyramidal geometry around Cu. Fluorinated complexes 1 and 3 were found to consist of extensive intermolecular interactions while 2 and 4 contained no such interactions. Their optical band gap was around 1.4 eV which indicates semiconducting property of the complexes. Moreover, the flourous complex 3 was found to possess significant activity against Bacillus subtilis and Escherichia coli and good activity against Micrococcus luteus. A similar trend was observed in their DNA-binding potency studied through absorption as well as electrochemical solution studies yielding Kb values 1.494 × 104, 1.342 × 104 and 1.411 × 104 M−1 and 7.547 × 104, 2.457 × 104 and 3.667 × 104 M−1 for 1–3, respectively. The electronic structures of the complexes elucidated using density functional theory ab-initio calculations confirmed the Intermediate states which play important role in the enhancement of the optoelectronic properties. The structure and properties of the flourous complexes were found different than their non-flourous analogues which was attributable to fluorine.

Synthesis, structure, spectroscopy, thermal analysis and electron spin resonance of classical paddle–wheel binuclear and unusual polynuclear copper(II) compounds with benzoate and salicylamide

Two copper(II)benzoate compounds formulated in a fashion type of [Cux[RCOO]yLz] which are compound 1 or [Cu(C6H5COO)2(C6H5(OH)CONH2)]2 and compound 2 or [Cu(C6H5COO)(H2O)2]n·n(C6H5COO)·nH2O, {where (C6H5COO) = benzoate or (C6H5(OH)CONH2) = salicylamide}, have been successfully synthesized and characterized. Single crystal X-ray diffraction results confirmed the triclinic unit cell with a space group of P1¯ of the classical paddle–wheel binuclear compound 1 and the monoclinic unit cell with a space group of C2/c of polynuclear compound 2. Novel binuclear 1 has salicylamide as ancillary ligand and consists of a distorted square pyramidal [CuO4 + O] chromophore. Polynuclear 2 consists of the monomeric [Cu(C6H5CO)(H2O)2]n+ moiety which is furthered tribridged by coordinated ligands, generated the octahedral [CuO4 + O2] core and the polymeric [Cu(C6H5CO)(H2O)2]n+ chain. Compound 2 is stabilized by water and benzoate counter parts via CH⋯O and CH⋯π weak hydrogen bondings. The Fourier-Transform infrared spectrometer as well as the solid state ultraviolet visible spectra confirmed their components, geometries and weak interactions. The thermogravimetry analysis of compounds 1 and 2 started with the releasing of water molecules and were followed by the decompositions of the organic ligands. The thermograms also indicated the strong and extensive hydrogen bond interactions. The final thermal decomposition products were copper oxide. The electron spin resonance (ESR) spectra measured at room temperature illustrating the signals of triplet. The broader field ESR spectra of 2 than 1 are also noticed.

Molecular Structural Motifs and O2 Activation Inspired by Enzymes and Solid Catalysts

The active sites found on the surfaces of heterogeneous catalysts, in enzymes and in solution chemistry bear more resemblance with regard to structure and reactivity than usually assumed. This is illustrated in this perspective article with a few precedent cases showing how the different areas may benefit from each other, when treated together. Findings concerning the methane-oxidizing sites inherent to oxygenated Cu-ZSM-5 are discussed with a view on the active site of the pMMO and models thereof. Polydentate siloxide ligands were found suitable to simulate the ligation of transition metal ions by zeolite frameworks or silica surfaces, so that corresponding iron complexes turned out to be valuable spectroscopic models for the active sites of iron-modified zeolites. Polynuclear copper siloxides proved advantageous precursors for the generation of novel heterogeneous oxidation catalysts. Combining the findings that chromium sites on silica supports possess unique properties and that chromium(II) complexes in solution exhibit interesting reactivities towards dioxygen led to the development of chromium(II) siloxide compounds with unique features for O2 activation.

Synthesis and Crystal Structure of a Polymeric Copper(II) Complex Derived from 2-Hydroxy-5-methylbenzaldehyde Oxime with Antibacterial Activities

A centrosymmetric O-bridged polynuclear copper(II) complex, [CuL2]n, where L is the deprotonated form of the Schiff base ligand 2-hydroxy-5-methylbenzaldehyde oxime, has been prepared and characterized by IR, UV and single-crystal X-ray determination. There is a crystallographic inversion center in the complex. The Cu atom in the complex is coordinated by the phenolate oxygen, imino nitrogen and hydroxyl oxygen atoms from two Schiff base ligands, forming octahedral geometry. The complex was tested in vitro for its antibacterial activity.