Copper Acetate Complex Research Articles

Photochemical Vapor Generation of Halides in Organic-Acid-Free Media: Mechanism Study and Analysis of Water Samples.

Herein, we report a discovery that photochemical vapor generation (PCVG) of halides (bromide, chloride, and fluoride) can be realized in organic-acid-free media, with figures of merit comparable to those in classical scenarios employing acetic acid. Metal acetates, copper salts, and mixtures of different acetates and copper salts were evaluated for their performance in facilitating PCVG of halides; the formation of copper acetate complexes turned out to play a crucial role. Methyl halides (CH3X, X = Br, Cl, F) were identified by gas chromatography-mass spectrometry (GC-MS) as principal volatile compounds. Several important intermediate species, including cuprous ions (Cu+), methyl (•CH3), and hydroxyl (•OH) free radicals, were confirmed using cuproine, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), and coumarin as a chromogenic agent, radical tracer, and fluorescence probe based on UV-vis, GC-MS, and fluorescence spectroscopy, respectively. The ligand to metal charge transfer (LMCT) between acetate and copper and the charge transfer to solvent (CTTS) excitation of halides were considered to account for the generation of methyl halides in organic-acid-free media. The presence of 100 and 200 μg mL-1 of CuAc2, as well as sample delivery rates of 10.7 and 3.3 mL min-1, yielded limits of detection of 0.03 and 3 μg L-1 for Br- and Cl-, respectively, by inductively coupled plasma mass spectrometry (ICPMS). The method was applied to the analysis of bottled water and seawater, achieving spike recoveries between 92 and 101%.

Synthesis and structures of copper complexes bearing unsymmetric derivatives of (R,R)‐1,2‐diaminocyclohexane: An efficient catalyst for asymmetric Henry reaction

A series of Cu (II) complexes bearing asymmetric derivatives of (R,R)‐1,2‐diaminocyclohexane were synthesised and characterised. The X‐ray structures of the complexes showed distorted square planar geometry. The catalytic activities of in situ‐generated copper acetate complexes in the presence of 10 mol% of N,N‐diisopropylethylamine were evaluated in the asymmetric Henry reaction. The current catalysts showed high enantioselectivity (up to 99%) for (S)‐1‐nitro‐4‐phenylbutan‐2‐ol from the reaction of 3‐phenylpropanal and nitromethane.

Crystal structure of poly[[(acetato-κO){μ3-N-[(pyridin-4-yl)meth-yl]pyrazine-2-carboxamidato-κ(4) N:N (1),N (2):N (4)]copper(II)] dihydrate]: a metal-organic framework (MOF).

The title compound, [Cu(C11H9N4O)(CH3CO2)]·2H2O (CuL), is a hydrated copper acetate complex of the ligand N-[(pyridin-4-yl)meth-yl]pyrazine-2-carboxamide (HL). Complex CuL has a metal-organic framework (MOF) structure with a 10 (3) network topology. The ligand coordinates in a bidentate and a bis-monodentate manner, bridging three equivalent Cu(II) atoms via the pyridine N atom and the second pyrazine N atom. The Cu(II) atom has a fivefold coordination sphere, CuN4O, being coordinated to three N atoms of the ligand and the acetate O atom in the equatorial plane and to the second pyrazine atom in the apical position. This gives rise to a fairly regular square-pyramidal geometry. In the crystal, the water mol-ecules are linked to each other and to the three-dimensional framework via O-H⋯O hydrogen bonds. There are also a number of C-H⋯O hydrogen bonds present within the framework.

Structurally diverse copper complexes bearing NNO-tridentate Schiff-base derivatives as efficient catalysts for copolymerization of carbon dioxide and cyclohexene oxide.

Structurally diverse copper acetate complexes based on NNO-tridentate Schiff-base ligands were synthesized and characterized as mono-, di-, and trinuclear complexes with respect to varied ancillary ligands. Treatment of the ligand precursors (L(1)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-4-methylphenol, L(2)-H = 4-chloro-2-(1-((2-(dimethylamino)ethyl)imino)ethyl)phenol, and L(3)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methylphenol) with Cu(OAc)2·H2O (1 equiv) in refluxing ethanol afforded five-coordinate mono- or bimetallic copper complexes ([(L(1))Cu(OAc)(H2O)] (1); [(L(2))Cu(OAc)(H2O)] (2); [(L(3))2Cu2(OAc)2] (3)) in high yields. Dinuclear copper acetate analogue [(L(1))2Cu2(OAc)2] (4) resulted from treatment of L(1)-H as the ligand precursor in refluxing anhydrous MeOH with equimolar proportions of metal acetate salt under a dry nitrogen atmosphere. However, a trinuclear complex, [(L(4))2Cu3(OAc)4] (5), was obtained on utilizing 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methoxyphenol (L(4)-H) as the proligand under the same synthetic route of 1-3; this complex was also synthesized in the reaction of L(4)-H and copper(II) acetate monohydrate in the ratio of 2:3, giving a quantitative yield. All complexes are active catalysts for copolymerization of cyclohexene oxide (CHO) and CO2 without cocatalysts. In particular, dinuclear Cu complex 3 performed satisfactorily to produce polycarbonates with controllable molecular weights and high carbonate linkages. These copper complexes are the first examples that are effective for both CO2/CHO copolymerization and formation of polymers in a controlled fashion.

ChemInform Abstract: Copper‐Mediated Oxidative Direct C—C (Hetero)aromatic Cross‐Coupling

AbstractReview: 38 refs.

Highly Active Dinuclear Copper Catalysts for Homogeneous Azide–Alkyne Cycloadditions

AbstractThe main feature of the herein presented class of molecularly defined catalysts for the copper‐catalyzed azide–alkyne cycloaddition reaction is the presence of two copper centres in one catalyst molecule. We report the facile three‐step synthesis of two representative bis‐NHC‐dicopper complexes as well as their catalytic performance in the azide–alkyne cycloaddition. A screening with one of these complexes has proved its wide applicability and excellent performance as homogeneous catalyst in various organic solvents and with different alkyne and azide substrates.

Copper-mediated oxidative direct C–C (hetero)aromatic cross-coupling

Some new types of copper-mediated intermolecular oxidative direct C-C (hetero)aromatic cross-couplings are described. A combination of the simple CuCl(2) salt and molecular oxygen allows 1,3-azoles to couple with terminal alkynes directly to form the corresponding heteroarylacetylenes. This direct version of Sonogashira-type coupling can be applied to the reaction with polyfluoroarenes. A copper acetate complex enables direct biaryl coupling between 2-arylazines and 1,3-azoles even in the absence of any palladium catalysts. Moreover, the Cu-based protocol can be extended to the coupling with indoles and pyrroles, in which a catalytic variant is also possible by using an ideal co-oxidant, atmospheric oxygen. On the other hand, a copper-promoted annulative direct coupling of o-alkynylphenols and -anilines with 1,3-azoles can provide a unique dehydrogenative approach to C3-azolylbenzoheteroles from nonhalogenated and nonmetalated starting materials. In addition, a related N-azolylindole synthesis from similar substrates is also disclosed.

Aromatic and Aliphatic Thiol Self-Assembled Monolayers on Au: Anchoring and Delivering Copper Species

The immobilization of dinuclear copper(II) acetate complexes (Cu2(CH3COO)4·2H2O) on self-assembled monolayers (SAMs) of different aliphatic and aromatic thiols with oxygen and nitrogen donors at the end group is investigated on preferentially oriented (111) gold surfaces (Au(111)). The Cu species are immobilized at the outer plane of these terminal groups by the interaction of the terminal moiety of the functionalized SAMs. The highest electrochemical activity for the Cu(II)/Cu(I) redox couple is found for the metallic complexes immobilized on SAMs of short thiols, irrespective of their aliphatic or aromatic character, or the nature of the terminal group of the linking molecule, suggesting that direct tunneling is the main path for charge transfer to the Au substrate. Even though a progressive demetalation of the copper acetate complex immobilized on N-terminated SAMs by the release of Cu ions to the solution is induced by repeated potential scans, this process is negligible for Cu species immobilized on ...

Quantum discord in spin-cluster materials

The total quantum correlation (discord) in Heisenberg dimers is expressed via the spin-spin correlation function, internal energy, specific heat or magnetic susceptibility. This allows one to indirectly measure the discord through neutron scattering, as well as calorimetric or magnetometric experiments. Using the available experimental data, we found the discord for a number of binuclear Heisenberg substances with both antiferro- and ferromagnetic interactions. For the dimerized antiferromagnet copper nitrate Cu(NO_3)_2*2.5H_2O, the three independent experimental methods named above lead to a discord of approximately 0.2-0.3 bit/dimer at a temperature of 4 K. We also determined the temperature behavior of discord for hydrated and anhydrous copper acetates, as well as for the ferromagnetic binuclear copper acetate complex [Cu_2L(OAc)]*6H_2O, where L is a ligand.

Supercritical carbon dioxide, a new medium for aerobic alcohol oxidations catalysed by copper-TEMPO

The copper catalysed aerobic oxidation of selected alcohol substrates in supercritical carbon dioxide (scCO(2)), employing a range of simple copper(II) catalyst compounds, is here described. The copper acetate complex of polydimethylsiloxane (PDMS) functionalised pyridine (1), compound 2, has previously been synthesised and characterised by us and its solubility in scCO(2) demonstrated. Due to this solubility we anticipated that the selective aerobic oxidation of alcohols to aldehydes could be homogeneously catalysed by this compound in scCO(2) in combination with the co-catalyst 2,2,6,6-tetramethylpiperidin-1-yloxy free radical (TEMPO). Our initial results showed that complete oxidation of 4-nitrobenzyl alcohol was achieved within 4 h of reaction. However, the activities of analogous copper derivatives containing simpler pyridine substituents, [Cu(AcO)(2)(py)](2) and [Cu(AcO)(2)(4VP)](2) (4VP = 4-vinylpyridine), were shown to be similar, in spite of their negligible solubility in scCO(2). When we repeated the reactions in highly non-polar hexane rather than scCO(2) similar observations were made. In both cases, as 2 is soluble and the pyridine analogues are not, a much higher reaction rate was anticipated for 2 as it is the only compound capable of homogeneous catalysis. However, in some cases slightly better activities were observed for [Cu(AcO)(2)(py)](2) rather than for the PDMS functionalised analogue, 2. Thus, despite poor catalyst solubility typically being very inhibitory in this type of catalytic process, in this system solubilisation of the catalyst is not necessary. In continuation the activity of silica supported copper complexes was therefore investigated. Employing such catalysts the 4-nitrobenzyl and benzyl alcohol substrates were completely oxidised to the corresponding aldehydes in scCO(2), this time employing lower catalyst loadings. Other types of alcohol substrate showed more limited conversions however. To conclude, alcohol oxidation in the non-conventional green solvent scCO(2), with the benign terminal oxidant, dioxygen, and simple, cheap, easily prepared metal catalyst compounds was demonstrated. This is the first copper-TEMPO catalysed alcohol oxidation system in scCO(2) to be described.

Magnetic properties of copper(II) complexes with some hydrazones of substituted salicylaldehydes

A series of novel mono-and binuclear copper(II) complexes with substituted salicylaldehyde acylhydrazones H2L of the formula CuL · xH2O (x = 0 and 1) and [Cu(HL)](ClO4)(CH3OH) were synthesized. The isolated dimeric complexes of copper acetate were found to exist as isomers with different bridging atoms. In dimers showing a superexchange between the paramagnetic centers through bridging phenoxide O atoms, the antiferromagnetic exchange couplings were much stronger than those in complexes with bridging O atoms of the a-oxyazine fragment.

Bis(acetato-κ2O,O′)diaquacopper(II)

A new monomeric copper acetate complex, [Cu(C2H3O2)2(H2O)2], was obtained unexpectedly by the reaction of Cu2(CO3)2(OH)2·xH2O, acetonitrile, ammonia and water under hydro­thermal conditions. The structure contains a dis­crete centrosymmetric diacetatodiaqua­copper(II) complex and the CuII atom is coordinated by four O atoms from two acetate anions and two water mol­ecules, giving a distorted octa­hedral geometry.

Analysis of Weak Interactions in the Crystal Packing of Inorganic Metalorganic Hybrids Based on Keggin Polyoxometalates and Dinuclear Copper(II)−Acetate Complexes

Reaction of in situ generated copper-monosubstituted Keggin polyoxometalate (POM) and copper-phenanthroline complexes in potassium or sodium acetate buffers led to the formation of the potassium salt of [[SiW(11)O(39)Cu(H(2)O)][Cu(2)(phen)(2)(H(2)O)(ac)(2)]](4-) (1) and [[Si(2)W(22)Cu(2)O(78)(H(2)O)][u(2)(phen)(2)(H(2)O)(ac)(2)](2)](8-) (2, where phen = phenanthroline and ac = acetate) hybrid polyanions, respectively. Both compounds are the first discrete mono- and bimolecular transition-metal-substituted Keggin POMs that support a binuclear copper-acetate complex. Despite the different nature of the POMs, the crystal packing of the two compounds is closely related, being formed of hybrid parallel layers that give rise to an alternate sequence of inorganic and metalorganic regions. This packing type seems to be determined by the extensive network of weak intermolecular interactions established by the dicopper complexes, as a Hirshfeld surface analysis shows. Electron paramagnetic resonance studies indicate that both the supported [Cu(2)(ac)(2)(phen)(2)(H(2)O)](2+) complexes and the copper(II)-monosubstituted POMs are magnetically isolated.

Copper(II) acetates with aliphatic/heterocyclic amines

Three copper acetate complex compounds, namely Cu(CH3COO)2(en)2·2H2O (I), Cu(CH3COO)2(tn)2(II) and Cu2(CH3COO)4(pyz) (III) (en=ethylenediamine, tn=1,3-diaminopropane, pyz=pyrazine), were prepared and characterized during heating in argon by thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) using mass spectrometry (MS). The results of infrared spectroscopy (IR) were evaluated to be used as a spectroscopic criterion for the determination of the carboxylate binding mode in the compounds.

Copper(II) acetates with aliphatic/heterocyclic amines

Three copper acetate complex compounds, namely Cu(CH3COO)2(en)2·2H2 O( I), Cu(CH3COO)2(tn)2 (II) and Cu2(CH3COO)4(pyz) (III )( en=ethylenediamine, tn=1,3-diaminopropane, pyz=pyrazine), were prepared and characterized during heating in argon by thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) using mass spectrometry (MS). The results of infrared spectroscopy (IR) were evaluated to be used as a spectroscopic criterion for the determination of the carboxylate binding mode in the compounds.

Preparation of Silver Nanoparticles in Cellulose Acetate Polymer and the Reaction Chemistry of Silver Complexes in the Polymer

Copper complexes have been directly incorporated into cellulose acetate (CA) and the resulting light blue colored homogeneous films of 5-20 wt.% copper acetate complex concentrations are found to be thermally stable up to200 °C. The reaction chemistry of Cu in CA has been investigated by reacting them with small gas molecules such as CO, H 2 , D 2 , O 2 , NO, and olefins in the temperature range of 25-160 °C, and various Cu-hydride, -carbonyl, -nitrosyl, and olefin species coordinated to Cu sites in CA are characterized by IR and UV/ Vis spectroscopic study. The reduction of Cu(II) complexes by reacting with H 2 gas at the described conditions results in the formation of Cu 2 O and copper metal nanoparticles in CA, and their sizes in 30-120 nm range are found to be controlled by adjusting metal complex concentration in CA and/or the reduction reaction conditions. These small copper metal particles show various catalytic reactivity in hydrogenation of olefins and CH 3 CN; CO oxidation; and NO reduction reactions under relatively mild conditions.

Picolinamide–Cu(Ac) 2-imprinted polymer with high potential for recognition of picolinamide–copper acetate complex

In this report, with semi-empirical quantum method, we have studied the conformation and energy of supermolecule composed of picolinamide and its positional isomers with methacrylic acid. We tried to explore the reason why picolinamide was not likely to show imprinting effect when using methacrylic acid as functional monomer in our previous work. In order to produce imprinting effect, which was not achieved based on hydrogen bonding interaction, we have synthesized a molecular-imprinted polymer (MIP) based on copper ion coordination in prepolymerization. The complex in prepolymerization was composed of copper(II), acetate, picolinamide and 4-vinylpyridine (4-Vpy). Suprisingly, the MIP had high selectivity to picolinamide–copper acetate complex, and changes of either copper ion, picolinamide or acetate would result in decrease in the imprinting effect. This is also the first example where the high selective recognition of the MIP to its template was achieved mainly by inhibiting the binding of non-template rather than enhancing the binding of the template. And this report can be also looked upon as a first step towards the solution to the problem of imprinting of template that contains intramolecular hydrogen bond.

Spectrophotometric Studies of the Coordination Polymers Based on Poly(8-Hydroxyquinoline) Matrix

Incorporation of various metal ions into a poly(8-hydroxyquinoline) (PHQ) matrix via a complexation mechanism to form the corresponding coordination polymers was investigated experimentally and computationally. TGA, DTG, MS, and elemental analysis measurements show that the polymeric chelates of copper(II) ion with the PHQ matrix have a hydrophilic nature about two-times stronger than the salt (i.e., copper acetate monohydrate). The results of DSC, TGA, and DTG suggest that the PHQ-Cu(II) matrix is more thermally stable than the copper acetate complex. A first-order derivative treatment of the UV-visible absorption spectra of the matrixes under investigation is sensitive to at least 1.5-times that of the normal (zero-order derivative) spectra. Analysis of the absorbance vs. mole fraction data for metal ions such as Cu(II), Ni(II), Co(II), and Fe(III), which are coordinated to the PHQ matrix, afforded information about the equilibria that prevailed in solution. The largest stability constant (log β) corresponds to a stiochiometric ratio of 2PHQ:1Mn+. The results are supported by elemental analysis, TGA, DTG, and mass spectroscopic measurements, and are consistent with molecular mechanics (MM+) calculations. A simple, rapid and sensitive method for the spectrophotometric determination of trace amounts of Cu(II) ion in solution by coordination with the PHQ matrix is proposed. The method has been applied successfully to the determination of Cu(II) ion in Heamoton capsule samples (mg/g). The proposed method is in excellent agreement with the determination of Cu(II) ion by atomic absorption spectrometry.

Activation of dioxygen by copper complexes incorporated in molecular sieves

The activation of dioxygen, at ambient conditions, by dimeric copper acetate complexes incorporated in molecular sieves Y, MCM-22 and VPI-5, in the oxidation of phenols to ortho diphenols and diphenols to o-quinones is reported. l-tyrosine is oxidised to l-DOPA, phenol to catechol, catechol to ortho benzoquinone and cresols to the corresponding ortho dihydroxy and o-quinone compounds. The incorporated copper complexes have been characterized by IR, UV and ESR spectroscopies. A linear correlation between the concentration of the copper acetate dimer in the molecular sieve (from ESR) and the conversion of l-tyrosine suggests that the dimeric copper atoms are the active sites in the activation of dioxygen. The catalytic efficiency (turnover numbers) of the copper atoms are higher in the incorporated state compared to that in ‘neat’ copper acetate. Our results indicate that copper acetate dimers in molecular sieves mimic both the monophenolase and diphenolase catalytic activity of the monooxygenase enzyme, tyrosinase.

Indirect flow-injection determination of tannins in wines and tea by atomic absorption spectrometry

An automatic continuous precipitation system for the indirect determination of tannins in foods based on the standard gravimetric method was developed as an alternative to the Official Methods of Analysis based on the Folin-Ciocalteu reagent. Tannins were precipitated by injecting the copper-acetate complex into the sample, and the unprecipitated copper was determined by atomic absorption spectrometry. The calibration graph was linear over the range 1–25 μg ml −1 tannic acid, and the relative standard deviation for determination of 10 μg ml −1 tannic acid was 2.0%. The 3σ detection limit was 0.7 μg ml −1. No compounds normally found in wines or tea had any effect on the determination. The results obtained in the analysis of 11 wines and 5 teas are critically compared with those provided by the Folin-Ciocalteu method.