Neutral Copper Research Articles

Bis(2-amino-4,6-dimethylpyrimidine-κN)bis(isophthalato-κ2O,O′)copper(II) 2-amino-4,6-dimethylpyrimidine disolvate

The title compound, [Cu(C8H5O4)2(C6H9N3)2]·2C6H9N3, is a neutral mononuclear copper(II) complex. The Cu2+ cation lies on an inversion centre, coordinated by the N atoms from two 2-amino-4,6-dimethyl­pyrimidine ligands and four O atoms from two chelating isophthalate ligands, in a distorted octa­hedral configuration. The asymmetric unit also contains a 2-amino-4,6-dimethyl­pyrimidine solvent mol­ecule. The crystal structure is stabilized by a network of O—H⋯N, N—H⋯O and N—H⋯N hydrogen bonds and π–π stacking inter­actions, forming a three-dimensional supra­molecular structure.

Tris[bis(μ-1,10-phenanthrolin-2-olato)dicopper(I)] monosodium trihydrogen β-octamolybdate hemihydrate

The title compound, Na[H3Mo8O26][Cu2(C12H7N2O)2]3·0.5H2O, contains neutral dinuclear copper(I) complexes and infinite chain-like polyoxoanions comprising β-[Mo8O26]4− units linked by Na+ cations which lie on centres of inversion. The polyoxoanion chains are protonated, rendering them neutral.

Structure and biological properties of the copper(II) complex with the quinolone antibacterial drug N-propyl-norfloxacin and 2,2′-bipyridine

The neutral mononuclear copper complex with the quinolone antibacterial drug N-propyl-protected norfloxacin, Hpr-norfloxacin, in the presence of the nitrogen donor heterocyclic ligand 2,2′-bipyridine has been prepared and characterized. The crystal structure of (chloro)(2,2′-bipyridine)(pr-norfloxacinato)copper(II), 1, has been determined and refined with X-ray crystallography. X-band electron paramagnetic resonance (=EPR) spectroscopy at liquid helium temperatures from powdered samples indicates the presence of dimeric units in consistency with the crystal structure. In aqueous solutions of 1 the EPR behavior indicates mixture of dimeric and monomeric species. The antimicrobial activity of the complex has been tested on three different microorganisms and the best inhibition (MIC = 0.25 μg mL −1) has been exhibited against Escherichia coli. The study of the interaction of the complex with calf-thymus DNA has been performed with diverse spectroscopic techniques and has shown that complex 1 is bound to calf-thymus DNA by the intercalative mode. Potential anticancer cytostatic and cytotoxic effects of complex 1 on human promyelocytic leukemia HL-60 and human chronic myelogenous leukemia K562 cell lines have been investigated. Complex 1 shows an increased antiproliferative and necrotic effect on both HL-60 and K562 human leukemia cells in comparison to the free pr-norfloxacin.

A systematic study of ligand intermolecular interactions in crystals of copper(II) complexes of bidentate guanidino derivatives

The synthesis and X-ray structures of four neutral copper(II) complexes and one cationic complex incorporating bidentate alkyl N-(4-oxo-5,5-diphenyl-4,5-dihydro-1 H-imidazol-2-yl)imidocarbamate ligands are reported. The neutral complexes, which possess potential doublet (DA) hydrogen bonding motifs, form supramolecular structures based on synthons involving hydrogen bonding or phenyl embraces. The formation of sheets within the crystal through combination of these synthons, and the occurrence of guest molecules trapped in cavities between the sheets, are described. The cationic complex forms an extended hydrogen-bonded structure that incorporates nitrate ions. The structures of the five complexes are compared with others reported previously for complexes of related ligands.

Synthesis, structure and biological activity of copper(II) complexes with oxolinic acid

The neutral mononuclear copper complexes with the quinolone antibacterial drug oxolinic acid in the presence or not of a nitrogen donor heterocyclic ligand 1,10-phenanthroline, 2,2′-bipyridine or 2,2′-dipyridylamine have been synthesized and characterized with infrared, UV-visible and electron paramagnetic resonance spectroscopies. The experimental data suggest that oxolinic acid acts as a deprotonated bidentate ligand and is coordinated to the metal ion through the pyridone and one carboxylate oxygen atoms. The crystal structure of (chloro)(1,10-phenanthroline)(oxolinato) copper(II), 2, has been determined with X-ray crystallography. For all complexes a distorted square pyramidal environment around Cu(II) is suggested. The EPR (electron paramagnetic resonance) behavior of 2 in aqueous solutions indicates mixture of dimeric and monomeric species. The investigation of the interaction of the complexes with calf-thymus DNA has been performed with diverse spectroscopic techniques and showed that the complexes are bound to calf-thymus DNA. The antimicrobial activity of the complexes has been tested on three different microorganisms. The complexes show a decreased biological activity in comparison to the free oxolinic acid.

Crystal structure, spectroscopic, and biological study of the copper(II) complex with third-generation quinolone antibiotic sparfloxacin

The neutral mononuclear copper(II) complex with the quinolone antibacterial drug sparfloxacin has been prepared and characterized with IR, UV–vis, and EPR spectroscopies and X-ray crystallography. The interaction of the complex with calf-thymus DNA has also been investigated and the antimicrobial activity has been evaluated against three different microorganisms.

Neutral and cationic mononuclear copper(II) complexes with enrofloxacin: Structure and biological activity

The mononuclear copper complexes with the quinolone antibacterial drug enrofloxacin (=Herx) in the presence or not of a nitrogen donor heterocyclic ligand 1,10-phenanthroline (=phen) and 2,2′-bipyridine (=bipy) have been prepared and characterized. Interaction of copper(II) with deprotonated enrofloxacin leads to the formation of the neutral complex Cu(erx) 2(H 2O), 1, while the presence of phen or bipy leads to the formation of a neutral or a cationic mononuclear complex, respectively. The crystal structures of (chloro)(1,10-phenanthroline)(enrofloxacinato)copper(II), 2, and (aqua)(2,2′-bipyridine)(enrofloxacinato)copper(II) chloride, 3, have been determined with X-ray crystallography. The complexes have been studied with X-band electron paramagnetic resonance in aqueous solutions at liquid helium temperature. The study of the interaction of the complexes with calf-thymus DNA has been performed with diverse spectroscopic techniques and has showed that all complexes are bound to DNA by the intercalative mode. The antimicrobial efficiency of the complexes has been tested on three different microorganisms and the available evidence supports that the best inhibition is provided by Cu(erx) 2(H 2O) (minimum inhibitory concentration = 0.125 μg mL −1) against Escherichia coli and Pseudomonas aeruginosa.

Molecular Structure and Bonding of Copper Cluster Monocarbonyls CunCO (n = 1−9)

In this work we analyze CO binding on small neutral copper clusters, Cun (n = 1-9). Molecular structures and reactivity descriptors of copper clusters are computed and discussed. The results show that the condensed Fukui functions and the frontier molecular orbital theory are useful tools to predict the selectivity of CO adsorption on these small clusters. To get further insight into the CO binding to copper clusters, an energy decomposition analysis of the CO binding energy is performed. The Cs symmetry of the formed CunCO clusters (n = 1-8) allows the separation between the orbital interaction terms corresponding to donation and back-donation. It is found that, energetically, the donation is twice as important as back-donation.

Copper(II) complexes derived from di-2-pyridyl ketone N(4), N(4)-(butane-1,4-diyl)thiosemicarbazone: Crystal structure and spectral studies

Neutral copper(II) complexes with a tetradentate NNNS Schiff base have been synthesized using the ligand, di-2-pyridyl ketone N(4), N(4)-(butane-1,4-diyl)thiosemicarbazone (HL). A series of five binuclear complexes of HL with general stoichiometry CuLX [ X = Cl ( 1), Br ( 2), NO 3 ( 3), N 3 ( 4) and SCN ( 5)], another dinuclear complex [Cu 2LCl 3] ( 6) with copper(II) chloride, and a tetranuclear complex [Cu 4L 4(SO 4) 2] ( 7) with copper(II) sulfate were also synthesized. The crystal structure of [Cu 2L 2(SO 4)] 2 · 3H 2O has been determined by X-ray diffraction studies. Crystal analysis shows that the complex is tetranuclear with five coordinated copper centers.

The Evaluation of Liposome-Water Partitioning of 8-Hydroxyquinolines and Their Copper Complexes

Bioavailability and toxicity of mixtures are urgent research issues, but usually mixtures of exclusively organic chemicals or exclusively metals are investigated. In our study, we explored the role of combinations of hydrophobic ionogenic organic compounds (HIOCs) with copper (Cu2+)for uptake and bioavailability of metals and hydrophobic metal complexes in an in vitro membrane system. We investigated the influence of the interactions of copper and 8-hydroxyquinolines, both components used in formulations of pesticides, on their partitioning into liposomes, which are model systems for biological membranes and are composed of lipid bilayers made of phosphatidylcholine. The test set of compounds comprised the parent compound 8-hydroxyquinoline and 8-hydroxyquinolines with hydrophobic (e.g., 5-chloro-8-hydroxyquinoline, 5,7-dichloro-8-hydroxyquinoline, 5,7-dibromo-8-hydroxyquinoline) and with hydrophilic (e.g., 8-hydroxyquinoline-5-sulfonic acid) substituents. Hydrophobic 8-hydroxyquinolines facilitate the passive uptake of copper into phospholipid bilayers by complex formation. Not only the neutral species of the ligands and their neutral copper ligand complexes are significantly taken up into the membrane, but also the cationic and anionic species of the ligands and the cationic complexes. The neutral, anionic, and cationic species of 8-hydroxyquinoline and the hydrophobic substituted 8-hydroxyquinolines exhibit linear correlations between their logarithmic liposome-water partitioning coefficients (log Klipw) and the logarithmic octanol-water partitioning coefficients of their neutral species (log Kow, neutral). The neutral species show the strongest partitioning followed by the anionic and cationic species. The associated quantitative structure activity relationships describing the dependency of log Klipw of the various species from log Kow, neutral of the neutral ligand species have slopes between 0.9 and 1. In contrast, the partitioning of the neutral and cationic copper-8-hydroxyquinoline complexes is dependent on several factors including the hydrophobicity of the ligand, the effective molecular size, and the polarization of the complex itself. In consequence, there is no linear relationship between log Klipw of these complexes and log Kow of the neutral species of their ligands. The complexes with very bulky substituents showed a reduced uptake. The Klipw of the nominally neutral complexes, where Cu2+ is coordinated with two ligands, were a factor three to four higher than the Klipw of the positively charged complexes with only one ligand. Although liposome-water partitioning merely describes one element of the uptake process into biological membranes, it is a key process for bioavailability of hydrophobic compounds and, presumably, also plays a crucial role for biological uptake of the described metal organic complexes.

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

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

Speciation of copper by using a new fullerene derivative as a mixed-mode sorbent

A new fullerene derivative was synthesized by photochemical reaction of C60 fullerene and rubeanic acid in a toluene–ethanol medium. The synthetic procedure was optimized by UV–visible spectroscopy, using the spectrum for C60 fullerene as reference; C60–rubeanic acid derivative, a novel adduct of C60 fullerene, exhibits an increased absorption band between 425 and 500 nm corresponding to the maximum absorption of rubeanic acid. The dark brown solid obtained was characterized by elemental analysis, and XRD and solid state 13C CP–MAS NMR spectroscopies. The band observed at 61.8 ppm is typical of sp3 atoms in the modified fullerene that forms by addition of amines to double bonds in fullerene, which bond covalently to the rubeanic acid group to form a monoadduct. The C60–rubeanic acid derivative can thus be used as a mixed-mode sorbent material for the speciation of cationic and neutral species. The adsorptive potential of the new derivative as a model for the preconcentration of copper traces on the pendant group of rubeanic acid, and neutral copper complexes (e.g. the pesticide copper oxinate) on the fullerene core has for the first time been assessed in this work. Both species are initially retained by the derivative and subsequently discriminated by sequential elution with various reagents. The proposed automatic method can accurately resolve mixtures of both types of copper species in ratios from 1 : 17 to 17 : 1 with relative errors less than 7%.

Theoretical Study of the Interaction of Molecular Oxygen with Copper Clusters

A new method based on frontier orbital theory has been used to investigate the binding site of molecular oxygen to neutral and anion copper clusters. It has been shown that one can make useful predictions of the binding sites based on the knowledge of the donor local reactivity of the cluster using the condensed Fukui function, f(-)(Ff). In this way, it was found that Cu(3), Cu(5), and Cu(5)(-) have the highest reactivity toward molecular oxygen.

Structure-driven design and synthesis of chiral dioxocyclam derivatives

Based on an analysis of previously reported structures and a potential geometry fit with substrates, a new family of chiral dioxocyclam derivatives have been designed. The synthesis of those ligands was accomplished starting from l-proline and α- d-amino acids (converted to β-amino acids) with a key step of macrocyclization reaction of amino esters. All ligands were converted into neutral copper(II) complexes (amide groups underwent deprotonation of upon treatment of ligands with copper(II) acetate). The complexes exhibit the desired shape of their active surfaces, as proved by X-ray analysis.

Investigations into some aryl substituted bis(thiosemicarbazones) and their copper complexes

The synthesis of three bis(thiosemicarbazone) compounds formed by the reaction of benzil with either thiosemicarbazide, 4-methyl-3-thiosemicarbazide or 4-phenyl-3-thiosemicarbazide are reported. The compounds were characterised by NMR spectroscopy, mass spectrometry and in the case of benzil bis(4-methyl-3-thiosemicarbazone) and benzil bis(4-phenyl-3-thiosemicarbazone) by X-ray crystallography. Attempts to purify benzil bis(thiosemicarbazone) and benzil bis (4-methyl-3-thiosemicarbazone) by recrystallisation resulted in the isolation of cyclised products that were characterised by X-ray crystallography. The 3 bis(thiosemicarbazone) compounds were used to synthesise both Cu(II) and Cu(I) complexes. The copper(II) complexes were formed by the reaction of the proligands with copper(II) acetate which gave neutral copper(II) complexes in which the thiosemicarbazone is doubly deprotonated, acting as a dianionic ligand. The copper(II)-benzil bis(4-phenyl-3-thiosemicarbazonato) complex was characterised by X-ray crystallography to show the copper in an essentially square planar N 2S 2 environment. The copper(I) complexes were synthesised by reacting the bis (thiosemicarbazone) ligands with [Cu(CH 3CN) 4]PF 6 to give cationic complexes. The copper(I)-benzil-bis(thiosemicarbazone) complex was characterised by X-ray crystallography which revealed that the complex was a dimeric dication. Each of the benzil bis(thiosemicarbazone) ligands act as a bidentate N,S donor to each copper(I) atom, forming an overall helical structure in which each copper atom is in a strongly distorted tetrahedral N 2S 2 environment. Electrochemical measurements show that the copper(II)-benzil bis(thiosemicarbazonato) complex undergoes a reversible reduction at biologically accessible potentials.

Effects of variety and crude protein content on nutrients and anti-nutrients in lentils ( Lens culinaris)

Protein content was used as an indicator of environmental conditions for a study on varietal and environmental variation of proximate composition, minerals, amino acids and anti-nutrients of lentils. Four lentil varieties, each with three levels of protein content, were selected. Crude protein content ranged from 24.3% to 30.2%. Analysis of variance showed that both varietal and environmental conditions had a significant effect on starch content. Significant varietal differences were found in acid detergent fibre (ADF), neutral detergent fibre (NDF), fat, ash, calcium (Ca), copper (Cu), potassium (K), manganese (Mn), phosphorus (P) and Zinc (Zn). Protein showed significant effects on the amino acids, arginine and tryptophan. Variety had a significant effect on sucrose, stachyose, phytic acid, tannins and trypsin inhibitor activity (TIA). Major lentil components, protein and starch content were inversely correlated. K, Mn, P and Zn were negatively correlated with protein content. Tryptophan was the most deficient amino acid and the sulphur-containing amino acids were the second limiting amino acid in lentils. Raffinose was positively correlated with starch while negatively correlated with ADF.

Rational Design of Mono-, Bi-, and Tetranuclear Macrocyclic Oxamido−Metal Complexes via Stepwise Complexation

By using the macrocyclic oxamido-copper(II) complex as a building block and N 3 - and Cl- as auxiliary bridged groups, a binuclear complex and two tetranuclear complexes derived from the binuclear species have been prepared by stepwise synthesis and characterized. Their formulas are Cu(μ-exoO 2 )cyclam (1), [Cu(μ-exoO 2 )cyclamCu-(tmen)](ClO 4 ) 2 .H 2 O (2), {[Cu(μ-exoO 2 )cyclamCu(μ-1,3-N 3 ) 0.5 (tmen)] 2 {ClO 4 )4, [Cu(μ-exoO 2 )cyclamCu(μ-1,3-N 3 ) 0.5 (tmen)] 2 -(ClO 4 ) 2 } (3), and [Cu(μ-exoO 2 )cyclamCu(μ-Cl) 0.5 (tmen)] 2 (ClO 4 )3 (4), where tmen = N,N,N'N'-tetramethylethylene-diamine and (exoO 2 )cyclam = 1,4,8,11-tetraazacyclotradecanne-2,3-dione. The structure of complex 1 consists of the neutral copper(II) complex of the [14]N 4 macrocyclic oxamido dianion, and the packing of the molecules along the b orientation results in a novel one-dimensional wavelike chain through weak coordination bonds and hydrogen bonds. The structure of complex 2 consists of binuclear cations, a weakly coordinated water molecule, and perchlorate anions, and the structures of 3 and 4 consist of tetranuclear cations derived from binuclear species through azide and chloride ligands, respectively, and perchlorate anions.

Syntheses and X-ray characterization of metal complexes with the pentadentate thiosemicarbazone ligand bis(4-N-methylthiosemicarbazone)-2,6-diacetylpyridine. The first pentacoordinate lead(ii) complex with a pentagonal geometry

In this paper we describe the electrochemical synthesis and characterization of new neutral manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead complexes with the ligand bis(4-N-methylthiosemicarbazone)-2,6-diacetylpyridine, H4DAPTsz-Me. X-Ray structures of [Mn(H2DAPTsz-Me)(EtOH)2] 1, [Pb(H2DAPTsz-Me)] 3 and [Zn(H2DAPTsz-Me)]2.EtOH.2H2O 4, were also determined. In these complexes the ligand behaves as bis-deprotonated and SNNNS pentadentate. In the manganese complex the metal is heptacoordinated, in a distorted pentagonal-bipyramidal environment, with the N3S2 donor set of the ligand in the pentagonal girdle and two solvent molecules occupying the axial positions. In the lead complex 3 the metal is pentacoordinated, bound exclusively to the five donor atoms of the ligand, as a consequence of the existence of "inert pair effect". The bishelical zinc complex 4 shows each zinc atom with different coordination geometry, one octahedrally six-coordinate while the other is distorted tetrahedrally four-coordinate.

The use of a novel oxime derivative [Phenyl( N-methylaniline)ketooxime] as leach reagent in the Copper(II) hydrometallurgy

Phenyl( N-methylaniline)ketooxime, (HL), has been designed and synthesized at the Chemical Engineering Research Center—UNSA, following the structural pattern of the LIX compounds, with a yield of 85%. The novel oxime derivative (HL) has been characterized through its physical and physicochemical properties such as: melting point (245–248 °C), solubility in water (ca. 2.0 g/l), protonation constant (log K p, 5.7 in methanol), and an absorption maximum ( λ max) in the UV–visible spectra, at 365 nm, in methanol solution. Results obtained from leach experiments indicate that the novel oxime derivative in alkaline and hypochlorite aqueous solution solubilises copper selectively in the form of a neutral copper(II) complex (CuL 2), which remained stable during the experimental period in a pH range between 9 and 11 and redox potential ( E h) range between −0.145 and 0.047 V. The aqueous blue–purple copper(II) complex solution was characterized from its absorption spectra, showing a single peak at λ max = 610 nm. The use of the novel oxime derivative in the leaching process has enabled the copper to concentrate from 0.82% in the ore to ca. 6.0 g/l in the pregnant leaching solution. On the other hand, electrowinning of the leach liquors has enabled the recovery of the copper and the release of the novel oxime derivative as a spent electrolyte, which was reused in a new leach process batch. Finally, by using Phenyl( N-methylaniline)ketooxime for copper hydrometallurgy, it is possible to propose an extraction process, which involves just two stages: leaching and electrowinning, thus requiring lower capital cost and energy consumption.

Synthesis, Characterization, and Reactivity of New Copper(II) Complexes of 2-Methylthio-N-(2-pyridylmethyl)acetamide

Copper(II) complexes were prepared with the new N(2)S(thioether) ligand 2-methylthio-N-(2-pyridylmethyl)acetamide (2-HL(N2S)). [Cu(2-L(N2S))Cl(MeOH)], which formed in the presence of excess triethylamine, is a distorted square pyramidal complex containing the ligand with the amide nitrogen deprotonated. The structurally analogous complex, [Cu(2-HL(N2S))Cl(2)], which formed in the absence of triethylamine, contains 2-HL(N2S) in the tautomeric imidic acid form. Neutral copper(II) N(2)S(thioether)S(thiolate) species were generated by addition of alkyl or aromatic thiolates to [Cu(2-L(N2S))Cl(MeOH)] and an unusual decomposition pathway was discovered.