Cupric Complexes Research Articles

Thiosulfate Leaching of Middle-Refractory Gold Ore with Ferricyanide as Oxidant

In order to decrease the consumption of lixiviant, study on dissolution of pure gold and middle-refractory gold ore using a novel thiosulfate leaching system with ferricyanide as oxidant was carried out. The results showed that the advantage of the novel system is that the thiosulfate consumption is negligible though the potential of ferricyanide is much higher than that of traditional cupric ammine complex. And compared to the ferric oxalate system, novel system could be used at relatively high pH condition which benefit to the stability of thiosulfate because ferricyanide can’t transfer to iron hydroxide in base solution. It is unlikely that very high dissolution rate of gold can be obtained using an air saturated thiosulfate- ferricyanide system without thiourea catalyst. However gold dissolution rate was increased with the increasing of concentration of ferricyanid in 5 mmol/L to 30mmol/L. When 0.1mmol/L thiourea was presented, the dissolution of gold approximately 1.5 times faster than that of in the absence of thiourea. Leaching of middle-refractory gold ore show that both of the consumption of thiosulfate and leaching rate was decreased compare to the traditional copper–ammonia thiosulfate system. Thiourea is not stable in base solution, but it was found that gold dissolution rates can be increased with a little thiourea ,the mechanism is still unclear.

An Efficient and Practical Protocol for Catalytic Hydrolysis of Nitriles by a Copper(I) Complex in Water

AbstractThe cuprous complex – Cu4I4(H2O)4 – has been isolated and employed for the catalytic hydrolysis of arenecarbonitriles, cinnamonitrile, and arylacetonitriles to the corresponding amides in pure water in high yields of up to 98%. The catalyst can be easily recovered and reused without loss of catalytic activity at least five times. Oxindole could be prepared successfully by one‐pot domino protocols based on this method.

Neutral cuprous complexes as ratiometric oxygen gas sensors

Four neutral mononuclear Cu(I) complexes, [Cu(pyin)(PPh(3))(2)] (1a), [Cu(pyin)(DPEphos)] (1b), [Cu(quin)(PPh(3))(2)] (2a) and [Cu(quin)(DPEphos)] (2b) (Hpyin = 2-(2-pyridyl)indole, Hquin = 2-(2-quinolyl)indole and DPEphos = bis(2-(diphenylphosphino)phenyl)ether) have been synthesized. X-Ray crystal structure analysis revealed that the central Cu(I) ion in all complexes is in a distorted tetrahedral coordination environment. All four complexes display the typical metal-to-ligand charge transfer (MLCT) absorption band at 371, 363, 413 and 402 nm, respectively. No emission was observed from any complexes in the solid state due to triplet-triplet annihilation. However, the complexes show unusual dual-emission originating from intraligand charge-transfer (ILCT) and MLCT transitions, when dispersed in a rigid matrix (e.g. PMMA) or in frozen CH(2)Cl(2). The oxidation potential of Cu(I)/Cu(II) in these neutral complexes, ∼0.5 V (vs. Ag/AgCl), is lower than those of cationic Cu(I) complexes. Films containing 10 wt% of these complexes in PMMA shows ratiometric fluorescent oxygen gas sensing property with a response ratio of 0.3-3.2 and response time of 3-4 s. Complex 2b acts as a ratiometric oxygen gas sensor with good reversibility through energy and electron transfer mechanisms under the loss of a counteranion.

Structural, spectroscopic, and electrochemical properties of tri- and tetradentate N3 and N3S copper complexes with mixed benzimidazole/thioether donors

Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene)amine (L(1)), bis(2-methylbenzimidazolyl)benzylamine (L(2)), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (L(3)), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me(2)L(2)), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me(2)L(3)) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L(3) and Me(2)L(3) give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu(2+) complexes [L(1)CuCl(2)] (1), [L(2)CuCl(2)] (2) and [Me(2)L(3)CuCl]ClO(4) (3(Me,ClO4)) are monomeric in solution according to ESI mass spectrometry data, as well as in the solid state. Their Cu(+) analogues [L(1)Cu]ClO(4), [L(2)Cu]ClO(4), [L(3)Cu]ClO(4) (4-6), [BOC(2)L(1)Cu(NCCH(3))]ClO(4) (4(BOC)), [Me(2)L(2)Cu(NCCH(3))(2)]PF(6) (5(Me)) and [Me(2)L(3)Cu](2)(ClO(4))(2) (6(Me)) are also monomeric in acetonitrile solution, as confirmed crystallographically for 4(BOC) and 5(Me). In contrast, 6(Me) is dimeric in the solid state, with the thioether group of one of the ligands bound to a symmetry-related Cu(+) ion. Cyclic voltammetry studies revealed that the bis(2-methylbenzimidazolyl)amine-Cu(2+)/Cu(+) systems possess half-wave potentials in the range -0.16 to -0.08 V (referenced to the ferrocenium-ferrocene couple); these values are nearly 0.23 V less negative than those reported for related bis(picolyl)amine-derived ligands. Based on these observations, the N(3) or N(3)S donor set of the benzimidazole-derived ligands is analogous to previously reported chelating systems, but the electronic environment they provide is unique, and may have relevance to histidine and methionine-containing metalloenzymes. This is also reflected in the reactivity of [Me(2)L(2)Cu(NCCH(3))(2)](+) (5(Me)) and [Me(2)L(3)Cu](+) (6(Me)) towards dioxygen, which results in the production of the superoxide anion in both cases. The thioether-bound Cu(+) centre in 6(Me) appears to be more selective in the generation of O(2)˙(-) than 5(Me), lending evidence to the hypothesis of the modulating properties of thioether ligands in Cu-O(2) reactions.

Experiences during Synthesis of a Dinucleating Spacer Incorporating 2-Chloropyridine Units Through Sandmayer Reaction

A bimetallic cuprous complex was accidentally reported, during synthesis of a dinucleating spacer incorporating two 2-chloropyridine units through Sandmayer reaction. The product was characterized by elemental analysis, FAB-Mass, FT-IR, UV, magnetic susceptibility and1H-NMR spectroscopic method. A possible mechanism is also proposed.

Synthesis and characterisation of neutral mononuclear cuprous complexes based on dipyrrin derivatives and phosphine mixed-ligands

Heteroleptic neutral mononuclear cuprous complexes with dipyrrin derivatives and phosphine mixed-ligands including 1,3,7,9-tetramethyldipyrrin (1), 5-phenyl-1,3,7,9-tetramethyldipyrrin (2), 2,8-dibromo-1,3,7,9-tetramethyldipyrrin (3), 1,9-dichloro-5-phenyldipyrrin (4), 1,9-dibromo-5-phenyldipyrrin (5), 5-pentafluorophenyl-1,3,7,9-tetramethyldipyrrin (6) and 1,5,9-triphenyldipyrrin (7) have been synthesized and fully characterized. The central Cu(i) atoms of these complexes in general formulas of Cu(1-6)(PPh(3))(2) (1a-6a) and Cu(1-6)(DPEphos) (1b-6b) [DPEphos = bis(2-diphenylphosphinophenyl)ether] all exhibit a pseudo-tetrahedral geometry, while complex Cu(7)(PPh(3)) (7a) is tricoordinated in a pyramidal conformation due to the large steric hindrance of ligand 7. The oxidation potentials assigned to oxidations of Cu(i)-Cu(ii) are extraordinarily low in the range of 0.36-1.02 V vs. Ag/AgCl compared with traditional [Cu(phen)(PP)](+) analogues. Their emission maxima range from 495 to 595 nm in dichloromethane at room temperature with quantum yields of 0.05-4.03% and lifetimes on the order of nanoseconds. Unlike the characteristic MLCT emission in cationic Cu(i) complexes, the emissions are assigned to the dipyrrin-centered intraligand charge transition (ILCT) based on the fact that the increased conjugation within the dipyrrinato anion leads to a weaker metal-ligand interaction, thus preventing the mixing of π orbitals of ligand and 3d orbitals of Cu(i) atom. This conclusion is also supported by electrochemical data and theoretical calculations.

Energetic cuprous azide complex: synthesis, crystal structure, and characterization

An energetic cuprous azide complex, [Cu2(2apyz)(N3)2] n (1) (2apyz = 2-aminopyrazine), has been synthesized through hydrothermal method by utilizing the reducibility of H3PO3 and structurally characterized by single-crystal X-ray diffraction. Complex 1 has a 2-D layer structure constructed from copper(I) bridged by azide and pyrazine. Catalysis research shows 1 can promote the burning rate of the main component of rocket propellant.

Complexation of penicillins and penicilloic acids by cupric ion.

Abstract A kinetic method was developed to study the interactions between cupric ion and penicillins G and V. Complexation was found to occur with the intact penicillins, followed by rapid hydrolysis of the complex into the corresponding penicilloic acid-cupric ion complex. The logarithmic stability constants for the interaction between cupric ion and penicillins G and V were found to be 2·61 and 2·24, respectively. In addition, the method of continuous variation was used to determine the logarithmic stability constants for the cupric ion-penicilloic acid complexes. These were found to be 4·20 and 4·50, for penicilloic V and G acids respectively.

Copper(II) assisted hydrolysis of 2,4,6-tris(pyrazol-1-yl)-1,3,5-triazine. Crystal and molecular structure of catena-[CuL(H2O)Cl]n (L = 2,4-dione-1,3,5-(1H)-triazin-1-amido)

This article describes the partial hydrolysis of the multidentate ligand 2,4,6-tris(pyrazol-1-yl)-1,3,5-triazine in the presence of copper(II), to give the anionic ligand 2,4-dione-1,3,5-(1H)-triazin-1-amido, which was isolated as the cupric complex catena-[CuL(H2O)Cl]n, where L is the amido ligand. No other hydrolysis products were isolated or identified.The complex defines a zigzag 1D covalent chain, along the b cell axis, through apical copper–oxygen bonds (Cu–N–C–O···Cu bridges).

Hydroxyquinoline based binders: Promising ligands for chelatotherapy?

We report here a thorough physico-chemical study of the coordination properties of clioquinol, an oxine-type active neurological drug in Alzheimer's disease, toward biologically relevant divalent metal ions (Cu, Zn, Ni, Co and Mn). Using a fruitful combination of electrospray mass spectrometry, absorption spectrophotometry and potentiometry, we have characterized the mono- and bis-chelated metal ion species. The determination of the stability constants showed a classical thermodynamic behavior along the studied series with the cupric complexes being by far the most stable species. Our data are discussed within the scope of Alzheimer's disease.

Phosphorescent Cuprous Complexes with N,O Ligands – Synthesis, Photoluminescence, and Electroluminescence

AbstractSix heteroleptic cuprous complexes, [L1Cu(PPh3)2](BF4) (1a), [L1Cu(DPEphos)](BF4) (1b), [L2Cu(PPh3)2](BF4) (2a), [L2Cu(DPEphos)](BF4) (2b), [L3Cu(PPh3)2](BF4) (3a), and [L3Cu(DPEphos)](BF4) (3b) {L1 = diphenyl(2‐pyridyl)phosphane oxide, L2 = diphenyl(8‐quinolyl)phosphane oxide, L3 = diphenyl(2‐pyridylmethyl)phosphane oxide, DPEphos = bis[2‐(diphenylphosphanyl)phenyl] ether}, were prepared and fully characterized. The electronic absorption spectra and quantum chemical calculations indicate that the lowest excited states of these complexes can be assigned to the metal‐to‐ligand charge transfer (MLCT) transition. In poly(methyl methacrylate) (PMMA) films, these complexes exhibit blue‐green to orange emissions with long lifetimes ranging from 7.5 to 28.6 μs. With wide energy‐band gaps of 3.50 and 3.28 eV, complexes 3a and 3b emit efficiently in 20 wt.‐% PMMA films with photoluminescence quantum efficiencies of 0.69 and 0.72, and emission maxima at 477 nm and 495 nm, respectively. Electroluminescent devices were fabricated with these N,O‐based CuI complexes as emitters. The best device performance, with a peak current efficiency of 4.9 cd/A, was obtained for 3b.

Formation of very stable and selective Cu(ii) complexes with a non-macrocyclic ligand: can basicity rival pre-organization?

The synthesis of ligand L based on a 2,6-bis[(N,N-bis(methylene phosphonic acid)aminomethyl] pyridine scaffold is described. Potentiometry combined with UV-Vis absorption spectrophotometric titrations were used to determine the protonation constants of the ligand and the stability constants of its corresponding Cu(II), Ni(II), Zn(II) and Ga(III) cations (0.1 M NaClO(4), 25.0 °C). The physico-chemical approach revealed very large stability constants for Cu(II) complexation (logK(CuL) = 22.71(7)) reflected in a very high pCu(II) value of ∼ 15.5 (pH = 7.4, [L](tot) = 10(-5) M, [Cu](tot) = 10(-6) M), close to those measured for the strong methylphosphonate functionalized cyclen chelators. Based on a literature survey, a correlation is proposed between the pK values of branched polyamine ligands and their stability constants for Cu(II) complexation, allowing for an estimation of the latter on the basis of the protonation constants of L. Ligand L was also shown to be very selective towards Cu(II) compared to the other cations studied (ΔlogK > 4). UV-Vis spectroscopy and kinetic measurements indicated that the formation of the cupric complexes with L is very fast, which, in combination with all other properties, makes it an excellent non-cyclic target for Cu(II) radiopharmaceutical within the frame of (64)Cu positron emission tomography imaging and radiotherapy.

Copper(I)/O2 Chemistry with Imidazole Containing Tripodal Tetradentate Ligands Leading to μ-1,2-Peroxo−Dicopper(II) Species

Cuprous and cupric complexes with the new imidazolyl containing tripodal tetradentate ligands {L(MIm), (1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine, and L(EIm), 2-(1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)ethanamine}, have been investigated to probe differences in their chemistry, especially in copper(I)-dioxygen chemistry, compared to that already known for the pyridyl analogue TMPA, tris(2-pyridyl)methyl)amine. Infrared (IR) stretching frequencies obtained from carbon monoxide adducts of [(L(MIm))Cu(I)](+) (1a) and [(L(EIm))Cu(I)](+) (2a) show that the imidazolyl donor is stronger than its pyridyl analogue. Electrochemical data suggest differences in the binding constant of Cu(II) to L(EIm) compared to TMPA and L(MIm), reflecting geometric changes. Oxygenation of [(L(MIm))Cu(I)](+) (1a) in 2-methyltetrahydrofuran (MeTHF) solvent at -128 degrees C leads to an intensely purple colored species with a UV-vis spectrum characteristic of an end-on bound peroxodicopper(II) complex [{(L(MIm))Cu(II)}(2)(mu-1,2-O(2)(2-))](2+) (1b(P)) {lambda(max) = 528 nm}, very similar to the previously well characterized complex [{(TMPA)Cu(II)}(2)(mu-1,2-O(2)(2-))](2+) {lambda(max) = 520 nm (epsilon = 12 000 M(-1) cm(-1)), in MeTHF; resonance Raman (rR) spectroscopy: nu(O-O) = 832 (Delta((18)O(2)) = -44) cm(-1)}. In the low-temperature oxygenation of 2a, benchtop (-128 degrees C) and stopped-flow (-90 degrees C) experiments reveal the formation of an initial superoxo-Cu(II) species [(L(EIm))Cu(II)(O(2)(*-))](+) (2b(S)), lambda(max) = 431 nm in THF) . This converts to the low-temperature stable peroxo complex [{(L(EIm))Cu(II)}(2)(mu-1,2-O(2)(2-))](2+) (2b(P)) {rR spectroscopy: nu(O-O) = 822 (Delta((18)O(2)) = -46) cm(-1)}. Complex 2b(P) possess distinctly reduced Cu-O and O-O stretching frequencies and a red-shifted UV-vis feature {to lambda(max) = 535 nm (epsilon = 11 000 M(-1) cm(-1))} compared to the TMPA analogue due to a distortion from trigonal bipyramidal (TBP) to a square pyramidal ligand field. This distortion is supported by the structural characterization of related ligand-copper(II) complexes: A stable tetramer cluster complex [(mu(2)-L(EIm-))(4)(Cu(II))(4)](4+), obtained from thermal decomposition of 2b(P) (with formation of H(2)O(2)), also exhibits a distorted square pyramidal Cu(II) ion geometry as does the copper(II) complex [(L(EIm))Cu(II)(CH(3)CN)](2+) (2c), characterized by X-ray crystallography and solution electron paramagnetic resonance (EPR) spectroscopy.

Synthesis and characterization of cyclohexene oxide functional polystyrene macromonomers by ATRP and their use in photoinitiated cationic polymerization

In this study, a novel well-defined macromonomer of epoxy end-functionalized polystyrene was synthesized by atom transfer radical polymerization (ATRP). The compound 3-cyclohexenylmethyl-2-bromopropanoate was synthesized by the condensation of 3-cyclohexene-1-methanol with 2-bromopropanoyl bromide. Subsequently, the epoxidation of the obtained 3-cyclohexenylmethyl-2-bromopropanoate using 3-chloroperoxybenzoic acid results in a new epoxy functional ATRP initiator. The ATRP of styrene (St) in bulk at 110 °C, by means of this initiator in conjunction with the cuprous complex Cu(I)Br/bipyridine, yields a well-defined macromonomer of polystyrene with an epoxy end group. GPC, IR, and 1H NMR analyses revealed that a low-polydispersity polystyrene with the desired functionality at the end of the chain was obtained. The photoinduced cationic polymerization of this macromonomer yielded graft and block copolymers.

Dioxygen Activation by Mononuclear Copper Enzymes: Insights from a Tripodal Ligand Mimicking Their CuM Coordination Sphere

A mononuclear cuprous complex is proposed as a novel in silico model for the Cu(M) active site of noncoupled copper monooxygenases. To the best of our knowledge, it is one of the first biomimicking models that allows one to recover the intimate structural features of the enzymatic oxygenated adducts and to gain clear-cut insights relevant to dioxygen activation by these enzymes.

Hydroxo-Bridged Dinuclear Cupric Complexes Encapsulated in Various Mesoporous Silicas to Mimic the Catalytic Activity of Catechol Oxidases: Reactivity and Selectivity Study

We report the synthesis and characterization of two hydroxo-bridged dinuclear cupric complexes, HPC [((phen)2Cu−OH−Cu(phen)2)3+, phen = 1,10-phenanthroline] and HBC [((bpy)2Cu−OH−Cu(bpy)2)3+, bpy = 2,2′-bipyridine], encapsulated in porous materials for the oxidation of 3,5-di-tert-butylcatechol (DTBC) to the corresponding quinone, 3,5-di-tert-butylquinone (DTBQ), to mimic catechol oxidases (COs). The separations of the two Cu(II) centers are 2.9, 3.51, and 3.65 A for CO, HPC, and HBC, respectively. The stability of dinuclear cupric complexes, turnover number (TON), and selectivity of DTBQ were examined in NaY zeolite (pore size 0.74 nm) and the solid mesoporous silicas (MPSs) MCM-41 (2.4 nm), MCM-48 (2.5 nm), and MAS-9 (9.0 nm). The studies showed that the MCM-41 and MCM-48 provided a better stability against the irreversible dissociation of dinuclear cupric complexes for their matching size, while NaY has too small and MAS-9 has too large pore size to stabilize these dinuclear copper complexes. The EPR s...

Replacement of a Nitrogen by a Phosphorus Donor in Biomimetic Copper Complexes: a Surprising and Informative Case Study with Calix[6]arene-Based Cryptands

The aim of the paper is to characterize Cu complexes in the P(Ar)N(3) environment provided by ligands derived from triphenylphosphine P(C(6)H(4)CH(2)NHR)(3) and compare their coordination behavior and reactivity with those obtained with all-nitrogen ligands such as tren. It is shown that coordination of the PN(3) ligand (R = iPr) to Cu(I) and Cu(II) leads to complexes whose coordination sphere is hardly controlled as they readily undergo decoordination of either one N or the P donor together with oxidation of the latter. In strong contrast, when grafted on the small rim of a calix[6]arene, the P(Ar)N(3) is geometrically constrained into a tripod that enforces the metal center to remain in the same environment with a P-Cu bond for both oxidation states. These calix[6]PN(3)-based Cu(I) and Cu(II) complexes react readily with exogenous ligands, making a comparison with calix[6]tren-based copper complexes possible. Indeed, reactivity studies in solution highlight very different behaviors. The complex [Cu(calix[6]PN(3))](2+) shows an unusual affinity for weak sigma-donors (e.g., MeCN > EtOH), while the analogous cuprous complex, [Cu(calix[6]PN(3))](+), displays a surprising affinity for hard O-donor ligands (EtOH, DMF), which has never been observed for the tren analogues. Even more surprising is the lack of reactivity of [Cu(calix[6]PN(3))](+) toward dioxygen, which contrasts strongly with the high reactivity of the [Cu(calix[6]tren)](+) complex. In an attempt to explain the observed differences in binding properties and reactivity, Density Functional Theory calculations and electronic spectra simulations were undertaken. They suggest that coordination of the soft P(Ar)(3) center allows to tune the metal ion properties, either by absorbing excess electron density from Cu(I), or by increasing the electronic density of Cu(II). This is due to the simultaneous presence of the phosphorus atom (sigma-donor) in apical position and the aromatic groups (pi-acceptors) bound to the P-atom.

Determination of dithiocarbamates; improvements to the method described in EN 12396-1 standard

A procedure to improve the performance and reliability of the method described in European standard EN-12396-1 is presented. A CS2 working range of 10–50 µg per 25 mL was validated. The quantification limit was lowered from 0.25 mg kg−1 to 0.05 mg kg−1 (200 g of sample matrix), in agreement with the Maximum Residue Limits for dithiocarbamates (DTCs). The procedure involves the measurement of the average absorbance at 374 nm and 435 nm, to allow for the equilibrium between the two coloured Cupric(II) complexes formed. Two main modifications of the decomposition and distillation apparatus assembly were introduced. One was the stabilization of the colour-forming reagent solution at 0°C to ensure stability of absorbance. The other was the inclusion of a bubbler trap with ethanol, to retain interfering compounds. The possible CS2 contamination by several types of protective gloves was also studied. Vinyl gloves, made according to the AQL 1.5 – EN 455-1/2 standard, did not interfere with the method.

The cerebral copper-protein complexes in hepato-lenticular degeneration studied by means of electron-spin-resonance technique.

The electron-spin-resonance spectra of cupric complexes existing in brains with hepato-lenticular degeneration were analyzed and quantitatively evaluated with regard to unit mass and compared with those of control brains. Compared with control specimens, the brains with Wilson's disease showed an approximately five–fold increase in copper content; but there were no detectable differences in the paramagnetic characteristics of the cupric complexes between the control and pathological brains. The content and paramagnetic spectrum of the iron complexes were found to be unchanged in the brains with Wilson's disease.

DNA Oxidative Cleavage Induced by the Novel Peptide Derivatives of 3‐(quinoxalin‐6‐yl)alanine in Combination with Cu(II) or Fe(II) Ions

Three model dipeptides containing 3-(2,3-di(pyridin-2-yl)quinoxalin-6-yl)alanine, 3-(dipyrido[3,2-a:2,3-c]phenazin-11-yl)alanine, and 3-(2,3-diphenylquinoxalin-6-yl)alanine were studied with respect to their ability to bind selected transition metal ions, such as Cu(II), Fe(II), Ni(II), Co(II), Mn(II), and Cr(III). It was found that only Cu(II) and Fe(II) ions could form stable complex species with the studied compounds. The ability to form the complexes correlated well with DNA damage experiments. Only the ferrous and cupric complexes are capable of generating both single- and double-strand scissions. However, double-strand breakages appear to be dominating lesions in the presence of hydrogen peroxide, especially for copper(II) containing systems. The quantity of breakage products in the presence of N-(3-(dipyrido[3,2-a:2,3-c]phenazine-11-yl)alanyl)glycine complexes was the highest as compared to the complexes of the remaining compounds. Moreover, this ligand was the only one that cleaved DNA in the absence of either Cu(II) or Fe(II) ions.