Trivalent Copper Research Articles

Enhanced oxidation of 2,4-dichlorophenol in ferrate(VI) and copper oxide system via the formation of trivalent copper ion and singlet oxygen.

Improving the activity of ferrate is one of the main research focus in environmental field. Here, we demonstrate a novel copper oxide (CuO)-Ferrate(VI) system wherein CuO plays a key role in activating Fe(VI) to effectively eliminate phenolic contaminants. The dominant reactive species were determined to be Cu(III) and 1O2, confirmed by in situ Raman spectroscopy, quenching experiments, and EPR tests. The results indicated that Fe(VI) preferentially reacts with CuO, forming Cu(III) and 1O2. Subsequently, deprotonated 2,4-dichlorophenol (2,4-DCP) was adsorbed with Cu(III) via electrostatic adsorption and was directly oxidized by Cu(III). Co-existing ion experiments demonstrated the strong stability of the CuO/Fe(VI) system against environmental background substances, maintaining effective removal efficiency over multiple cycles. In summary, this study highlights the potential advantages of CuO-assisted Fe(VI) activation, offering a new route for the efficient utilization of Fe(VI) in eliminating phenolic pollutants.

Insight into efficient degradation of pentacyclic and hexacyclic sulfonamide antibiotics by synthetic trivalent copper: Performance and mechanism

High valent metal species, including Mn(III), Fe(IV) and Cu(III), have been identified as key intermediates in the degradation of pollutants in many advanced oxidation processes. However, unlike Mn(III) and Fe(IV), the current exploration of the reaction activity and selective oxidation mechanism of Cu(III) towards pollutants with different structures is still quite limited. Herein, the copper(III) periodate was synthesized to investigate the reactivity towards six sulfonamide antibiotics (SAs) including typical two pentacyclic structures (sulfamethoxazole (SMX) and sulfathiazole (STZ)) and four hexacyclic structures (sulfadiazine (SDZ), sulfamerazine (SMR), sulfamonomethoxine (SMM) and sulfapyridine (SPD)). The results indicated that all SAs almost completely removed by Cu(III) system after 10 min with the molar ratio of approximately 3:1 (Cu(III):SAs) and Cu(III) direct oxidation played the most important role. SAs with 6-ring substituents were more readily degraded by Cu(III) than SAs with 5-ring substituents, and the presence of electron-rich group such as -CH3 and -S in ring substituent increased the reactivity towards Cu(III). The introduction of coexisting anions (Cl−, SO42− and HCO3−) hardly affected the degradation of SAs by Cu(III) oxidation, while the addition of HA to some extent inhibited SAs degradation. The solution pH greatly affected the degradation of SAs by Cu(III) and the removal efficiencies of SAs roughly followed the rule of neutral > acidic > alkaline. The degradation mechanism of SAs with 5-ring and 6-ring substituents in Cu(III) system mainly included amino nitration, self-coupling, hydroxylation, S-N cleavage in SAs with 5-ring substituents and SO2 extrusion in SAs with 6-ring substituents. Although the real water matrix inhibited the degradation of SAs to varying degrees, Cu(III) still played a satisfactory performance on SAs degradation especially for electron-rich structure.

Mechanistic Insight on the Aerobic Oxidation of Alcohols by Trivalent Copper from DFT Calculations

AbstractDensity functional theory (DFT) calculations were carried out to elucidate the mechanism of alcohol oxidation by a Cu(III) anilidosalen complex. The study considered singlet, broken‐symmetry singlet, and triplet states. During the first step the alcoholate binds to the copper, inducing valence tautomerism, transforming the Cu(III) complex into a Cu(II)‐alkoxyradical adduct. Subsequently, an “aniline” ring abstracts a hydrogen from the substrate with a low barrier, yielding a Cu(I) aniline complex and the aldehyde, akin to galactose oxidase. Catalyst re‐oxidation is coupled to dioxygen reduction. Initially, dioxygen is reduced by Cu(I) into superoxide, which binds to the metal. Protonation then yields either a Cu(II)‐hydrosuperoxo or a Cu(III)‐hydroperoxo adduct. Further protonation closes the catalytic cycle by releasing hydrogen peroxide.

Trivalent Copper Ion-Mediated Dual Oxidation in the Copper-Catalyzed Fenton-Like System in the Presence of Histidine.

The Cu(II)/H2O2 system is recognized for its potential to degrade recalcitrant organic contaminants and inactivate microorganisms in wastewater. We investigated its unique dual oxidation strategy involving the selective oxidation of copper-complexing ligands and enhanced oxidation of nonchelated organic compounds. L-Histidine (His) and benzoic acid (BA) served as model compounds for basic biomolecular ligands and recalcitrant organic contaminants, respectively. In the presence of both His and BA, the Cu(II)/H2O2 system rapidly degraded His complexed with copper ions within 30 s; however, BA degraded gradually with a 2.3-fold efficiency compared with that in the absence of His. The primary oxidant responsible was the trivalent copper ion [Cu(III)], not hydroxyl radical (•OH), as evidenced by •OH scavenging, hydroxylated BA isomer comparison with UV/H2O2 (a •OH generating system), electron paramagnetic resonance, and colorimetric Cu(III) detection via periodate complexation. Cu(III) selectively oxidized His owing to its strong chelation with copper ions, even in the presence of excess tert-butyl alcohol. This selectivity extended to other copper-complexing ligands, including L-asparagine and L-aspartic acid. The presence of His facilitated H2O2-mediated Cu(II) reduction and increased Cu(III) production, thereby enhancing the degradation of BA and pharmaceuticals. Thus, the Cu(II)/H2O2 system is a promising option for dual-target oxidation in diverse applications.

Synthesis of a trivalent copper complex for efficient degradation of antibiotic ofloxacin

Copper-based catalysts have been widely used in heterogeneous advanced oxidation processes (AOPs) to degrade emerging contaminants, with trivalent copper species (Cu(III)) often identified as crucial intermediates. However, the current understanding of the reactivity and potential oxidation mechanism associated with such reactive species remains quite limited. In the present study, a stable Cu(III) complex was synthesized, and its reactivity towards a typical fluoroquinolone antibiotic, ofloxacin (OFX), was comprehensively investigated. The results revealed that Cu(III) itself functioned as the primary oxidizing agent instead of secondary hydroxyl radicals generated during OFX decomposition, which exhibited high reactivity over a wide pH range (3.0–9.0) with molar ratio of Cu(III) to OFX between 1:2 and 3:1. Interestingly, prevalent constituents of natural water, including (bi)carbonate (0–10 mM), chloride (0–10 mM), nitrate (0–10 mM) and humic acid (0–30 mg/L), displayed minimal influence on the oxidation efficiency of Cu(III). Piperazine moiety was identified as the primary reaction site, and three different pathways including tertiary amine oxidation, hydroxylation, and N-demethylation process were proposed. The detailed oxidation mechanisms were further illustrated by density functional theory (DFT) calculations. This study contributes to the theoretical foundation for investigating the mechanism of Cu(III)-mediated oxidation of antibiotics.

Heterometallic complexes of trivalent copper dithiocarbamate with indium and gallium chloride

Heterometallic Cu−In and Cu−Ga complex salts, [Cu(III)(dedtc)2][In(III)Cl4] (1) and [Cu(III)(dedtc)2][Ga(III)Cl4] (2) (dedtc = −S2CNEt2, diethyldithiocarbamate), were synthesized from Cu(II)(dedtc)2, In(III)Cl3, and Ga(III)I3 in dichloromethane and acetone solvents. The trivalent copper complex [Cu(III)(dedtc)2]+ was produced by an oxidation reaction of Cu(II)(dedtc)2 and [M(III)Cl4]– (M = In, Ga) which exhibit a blue-shift of the C–N vibrational mode resulting from the high oxidation state of copper(III) cations. In the Cu−Ga complex salt (2), [Ga(III)Cl4]– was obtained by a halogen exchange reaction between Ga(III)I3 and CH2Cl2. Cu−In and Cu−Ga complex single crystals were grown in benzene and dichloromethane media. Their crystal structures were confirmed that [Cu(III)(dedtc)2]+ units formed distorted octahedral structures with infinite polymeric Cu–S chains surrounded by dimeric [M(III)Cl4]– and benzene. The crystal structures of 1 and 2 included benzene as a guest molecule due to strong noncovalent interactions of metal chloride anions.

Thermal effect on sulfamethoxazole degradation in a trivalent copper involved peroxymonosulfate system

Persulfate (PS) activated by thermal or homogeneous metals can generate reactive oxygen species (ROS) and high-valence-state metals for contaminants degradation, showing great potential for applications. However, thermal effect in peroxymonosulfate (PMS) system with high-valence-state metal is still ambiguous. In this study, divalent copper (Cu(II)) catalysis was taken to explore thermal effect on PMS performance. Results showed that the Sulfamethoxazole (SMX) removal efficiency in the Cu(II)/PMS system at 60 min increased by only 5.9% with temperature increase from 30 °C to 60 °C. Moreover, SMX removal efficiency was excellent at neutral or basic pH, best with PMS concentration of 2.4 mM, and slightly affected by Cu(II) concentration. The singlet oxygen (1O2) was identified as main active species at low temperature while sulfate radicals (SO4−) was more effective at high temperature with Cu(II) co-activation. Also, trivalent copper (Cu(III)) was an important active species. The higher Cu(III) content, the better SMX removal efficiency, but the stronger intermediates toxicity. In combination with removal efficiency and intermediates toxicity at different temperatures, 30 °C was the optimal reaction temperature. Overall, this study provides new perspective on utilization of waste heat and high-valence-state metal for organic wastewater treatment in PMS systems.

A novel seaweed re-greening method involving trivalent copper

For many decades, copper chlorophyllin is a widely used non-tar colorants for re-greening vegetables. However, this re-greening process is time-consuming and requiring a high amount of copper. A novel vegetable re-greening method that requires only seconds and a trace amount of copper was proposed. 10 mg/L copper acetate and 1 % ascorbic acid were coupled under 100 °C for 1 min to protect the green of kelp. We monitored ascorbic acid degradation, pheophytin a and copper-chlorophyllin complex. The results showed that Copper(III), which is a necessary intermediate, accelerates the reaction between pheophytins and copper in the presence of l-ascorbic acid during heating. This rapidly creates a copper chlorophyllin complex as a green pigment. We demonstrate that the mechanism of copper-based re-greening of green vegetables was elucidated. This study may promote the commercial applications of copper acetate and ascorbic acid in the field of green protection of vegetables.

Cu-catalyzed selective Oxygenation of Aryl C‒H Bonds with O2 and MnO2 as Terminal Oxidants

Herein, We present efficient methods for the copper-catalyzed selective oxidation of aromatic C-H bonds under O2 or/and MnO2 conditions. A range of 2-arylpyridines and 2-arylpyrimidines was used for the synthesis of controlled mono/di acetoxylative products in moderate to good yields (29-99%) in the presence of 20 mol% CuO(nano), O2 with HOAc/Ac2O as an acetoxy source and solvent. The mono selective hydroxylation of C-H bonds was also achieved with Cu(OAc)2 as the catalyst. For the reaction mechanism, the trivalent copper intermediate might be involved in the catalytic cycle.

The Theoretical Description for the Perylaldehyde Aldoxyme Anodic Electrochemical Determination, Assisted by the Novel Squaraine Dye Composite with Copper(ii) Sulfide Nanoparticles

In this work the perillaldehyde aldoxime electrochemical determination on an anode, modified by squaraine dye composite with copper sulfide nanoparticles is analyzed. The electroanalytical process involves the formation of trivalent copper species, capable to oxidize the analyte by two parallel mechanisms. The correspondent mathematical model, correspondent to both of them, has been developed and analyzed by means of linear stability theory and bifurcation analysis. The model analysis clearly shows that the composite of a squaraine dye in organic phase and bivalent copper sulfide in the inorganic phase may be an efficient electrode modifier for perillaldehyde aldoxime electrochemical determination on an anode. The electroanalytical process will be mostly kinetically-controlled with the possibility of the transfer to diffusion-controlled mode. On the other hand, both oscillatory and monotonic instabilities may be realized in the electroanalytical process, and their probability will depend on the direction of the electroanalytical scenario in the concrete conditions, due to the possibility of the formation of ionic compounds in the pre-surface layer. DOI: http://dx.doi.org/10.17807/orbital.v13i5.1501

Trivalent copper stabilised by acetylacetone dithiocarbazate Schiff base ligands: structural, spectroscopic and electrochemical properties.

The copper coordination chemistry of N2S2 Schiff base ligands derived from acetylacetone and S-methyl or S-benzyl dithiocarbazate (H3acacsR, R = Me, Bn) reveals a rich variety of products depending on the reaction conditions. The free ligands spontaneously cyclise to their pyrazoline isomers but ring-open upon complexation with CuII. In the absence of oxygen, the ligands form CuIIN2S2 complexes ([CuII(HacacsR)]) that have been characterised electrochemically, spectroscopically and structurally. Intermediates in the complexation reaction are observed with time-resolved UV-Vis spectroscopy. Upon exposure to air, a number of different complexes are formed. Facile oxidation of [CuII(HacacsR)] to the trivalent analogue [CuIII(acacsR)] occurs in air. This compound is the precursor to two further oxidation reactions; one to the ketone [CuII(acacsRO)] where a carbonyl group has been installed at the apical C atom of the acetylacetone moiety and another to afford the novel dinuclear complex [(CuIII(acacsR))2]. The presence of excess base (Et3N) favours formation of the dimer.

Factors and mechanisms that influence the reactivity of trivalent copper: A novel oxidant for selective degradation of antibiotics

Trivalent copper complexes are active intermediates in aquatic redox reactions that involve copper ions or structural copper, but their reactivity and selectivity toward pollutants remain unknown. We characterized copper(III) periodate, a representative trivalent copper compound, with phenol and several antibiotics as model contaminants. The results show that Cu(III) is highly reactive to phenol degradation; near-complete degradation was achieved after 10 min at a molar ratio of 3:1 (Cu[III]: phenol). Common alcohols, including methanol and 2-propanol, showed pH-dependent reactivity for Cu(III). In contrast to aquo trivalent copper ions that react rapidly with tert-butanol, Cu(III) showed limited reactivity toward tert-butanol. A mechanistic investigation showed that the degradation was caused by direct oxidation by Cu(III) and that no hydroxyl radicals were involved. Common water components such as chloride ions did not influence the reaction, which suggests that the use of Cu(III) may help mitigate the generation of chlorinated products. As a one-electron oxidant, Cu(III) showed high reactivity to degrade electron-rich compounds; the concentrations of sulfamethazine, sulfamethoxazole, and sulfadiazine (100 μg/L) were reduced to 1.8, 7.5, and 42.5 ng/L, respectively, after 2 min of reaction with 10 μM Cu(III). These results demonstrate a novel and highly efficient oxidant for selective removal of ubiquitous micropollutants from water bodies.

Theoretical Study of the Oxidation of Methane to Methanol by the [CuIICuII(μ-O)2CuIII(7-N-Etppz)]1+ Complex

The reactivity patterns of a series of trivalent copper complexes have been studied to gain a better understanding of the chemical reactions occurring at the active site of particulate methane monooxygenase (pMMO). In this study, hybrid density functional theory is used to study the oxidation of methane to methanol mediated by the [CuIICuII(μ-O)2CuIII(7- N-Etppz)]1+ complex. Reaction mechanisms in different spin states were explored. Based on the calculated free-energy profile, a mechanism is suggested for the reaction of the oxidation of methane to methanol. The first step (1 → 2) is a hydrogen transfer to the bridged oxygen in the Cu2O2 core from the methane to form a methyl radical. The second step (2 → 3) is the radical recombination, in which the bridged hydroxyl rotates upward and exposes the oxygen moiety toward the methyl radical to form methanol. The radical recombination step is rate-limiting, with a calculated free-energy barrier of 19.6 kcal mol-1, which is in good agreement with the experimental value of 18.4 kcal mol-1. The mixed valent bis(μ-oxo)CuIICuIII species in the Cu3O4 core is directly responsible for the C-H activation of methane.

Highly sensitive trivalent copper chelate–luminol chemiluminescence system for capillary electrophoresis chiral separation and determination of ofloxacin enantiomers in urine samples

A simple, fast and sensitive capillary electrophoresis (CE) strategy combined with chemiluminescence (CL) detection for analysis of ofloxacin (OF) enantiomers was established in the present work. Sulfonated β-cyclodextrin (β-CD) was used as the chiral additive being added into the running buffer of luminol–diperiodatocuprate (III) (K5[Cu(HIO6)2], DPC) chemiluminescence system. Under the optimum conditions, the proposed method was successfully applied to separation and analysis of OF enantiomers with the detection limits (S/N=3) of 8.0nM and 7.0nM for levofloxacin and dextrofloxacin, respectively. The linear ranges were both 0.010–100μM. The method was utilized for analyzing OF in urine; the results obtained were satisfactory and recoveries were 89.5–110.8%, which demonstrated the reliability of this method. This approach can also be further extended to analyze different commercial OF medicines.

The Trivalent Copper Complex of a Conjugated Bis-dithiocarbazate Schiff Base: Stabilization of Cu in Three Different Oxidation States

The new tribasic N(2)S(2) ligand H(3)ttfasbz has been synthesized by condensation of 4-thenoyl 2,2,2-trifluoroacetone and S-benzyl dithiocarbazate. On complexation with copper(II) acetate, spontaneous oxidation to the Cu(III) oxidation state is observed, and the complex [Cu(ttfasbz)] has been isolated and characterized structurally. Reduction to the EPR active Cu(II) analogue has been achieved chemically and also electrochemically, and in both cases, the process is totally reversible. The Cu(III/II) redox potential of the complex is remarkably low and similar to that of the ferrocenium/ferrocene couple. Further reduction to the formally monovalent (d(10)) dianion [Cu(I)(ttfasbz)](2-) may be achieved electrochemically. Computational chemistry demonstrates that the three redox states [Cu(ttfasbz)], [Cu(ttfasbz)](-), and [Cu(ttfasbz)](2-) are truly Cu(III), Cu(II), and Cu(I) complexes, respectively, and the potentially noninnocent ligand does not undergo any redox reactions.

A novel flow injection chemiluminescence method for the determination of ractopamine in urine by using trivalent copper

In this paper, a novel chemiluminescence method was proposed for the determination of ractopamine by combining with flow injection technology. The chemiluminescence system was based on oxidation of luminol by diperiodatocuprate(III) in the presence of ractopamine. The diperiodatocuprate(III) was obtained by complexation of copper in the trivalent oxidation state with periodate in a strong alkaline medium. Hereby under the optimum conditions, the relative CL intensity was proportional to the concentration of ractopamine over the range 1.0 × 10−9 g mL−1 to 1.0 × 10−6 g mL−1, with a limit of detection (3σ) of 3.4 × 10−10 g mL−1. The relative standard deviation (R.S.D.) was 2.1% for 5.0 × 10−8 g mL−1 ractopamine (n = 7). The sensitive method was successfully applied for the determination of ractopamine (ng mL−1) in urine samples. The possible mechanism of the CL reactions was also discussed.

Highly sensitive trivalent copper chelate-luminol chemiluminescence system for capillary electrophoresis detection of epinephrine in the urine of smoker

Epinephrine (EP) is one of the most important neurotransmitters and hormones. Some previous literatures show that there is a close relation between its release and smoking. To compare the levels of EP in urines of smokers and nonsmokers, a sensitive chemiluminescence (CL) system, luminol-diperiodatocuprate (III) (K5[Cu(HIO6)2], DPC), has been developed and validated for the determination of EP after CE separation. The DPC-luminol-EP CL reaction showed very intensive emission and fast kinetic characteristics, thus led to a high sensitivity in the flow-through detection mode for capillary electrophoresis. With the peak height as a quantitative parameter, the relative CL intensity was linear with the EP concentration in the range of 2.0–400ng/mL, with a limit of detection of 0.82ng/mL (S/N=3). The reproducibility was assessed by intra- and inter-day relative standard deviations (RSDs) for 11 replicate determinations of EP standard samples at low, medium and high concentrations. The intra- and inter-day RSDs for CL signals were 5.5%–6.6% and 6.1%–7.5%, respectively, and those for migration times were 3.4%–5.8% and 4.3%–6.3%, respectively. The presented method was successfully applied to the determination of EP in EP injection and urine samples of smokers and nonsmokers. The recovery test results for urine samples ranged from 86.5 to 112.0%, which demonstrated the reliability of this method. The results for urine sample detection indicate that the average level of EP in the urines of the smoker group is obviously higher than that in the urines of the nonsmoker group, which may demonstrate that smoking can stimulate the release of EP in human body.

Trivalent copper chelate‐luminol chemiluminescence system for highly sensitive CE detection of dopamine in biological sample after clean‐up using SPE

A transition metal chelate unstable at a high oxidation state, diperiodatocuprate (III) (K₅[Cu(HIO₆)₂], DPC), was synthesized and applied in the luminol-based chemiluminescence (CL) system for highly sensitive CE end-column detection of dopamine (DA). This method was based on the fact that DA enhanced the CL emission resulting from the reaction between luminol and DPC in alkaline medium. The DPC-luminol-DA CL system showed very intensive emission and very fast kinetic characteristics, thus resulting in a high sensitivity in flow-through detection mode for CE. Under optimal conditions, the linear range was 1.0 × 10⁻⁸-5.0 × 10⁻⁵ g/mL (R² = 0.9984) with a limit of detection of 6.0 × 10⁻⁹ g/mL (S/N = 3). The RSDs of the peak height and the migration time were about 4.2 and 2.4% for a standard sample at 3.0 × 10⁻⁶ g/mL (n = 5), respectively. The presented method has been successfully used for the determination of DA in commercial preparation and human urine samples after clean-up using SPE.

Micellar electrokinetic chromatography-chemiluminescent detection of biogenic amines using N-(4-aminobutyl)-N-ethylisoluminol as derivatization reagent and trivalent copper chelate as chemiluminescence enhancer

A facile, sensitive and universal method was established for analysis of biogenic amines using micellar electrokinetic chromatography coupled with chemiluminescent (CL) detection. It was found that diperiodatocuprate (III) (K5[Cu(HIO6)2], DPC), a transition metal chelate at unstable high oxidation state, could effectively enhance the reaction between luminol-type compound and hydrogen peroxide, to produce very strong CL signal. In addition, triethylamine was found to be able to effectively improve the yield of the derivatization reaction between biogenic amines and a luminol-type derivatization reagent, N-(4-aminobutyl)-N-ethylisoluminol (ABEI). Based on these facts, three biogenic amines were pre-column derivatized with ABEI, and post-column detected using high sensitive luminol-hydrogen peroxide-DPC CL system. Since the background was quite low, and the signal was quite strong, a considerable improved sensitivity was obtained. The presented method had been successfully applied to simultaneously analyze glycine, proline and phenylalanine with the detection limits (S/N=3) of 0.030μmolL−1, 0.23μmolL−1 and 0.21μmolL−1, respectively. To evaluate its potential application value, glycine in saliva and urine samples was detected using this method, and satisfied results were obtained. This approach can be further extended to detection of many other compounds such as peptides and drugs by using luminol-type derivatization reagent.

Effect of Metal Ions (Trivalent Chromium Ion and Copper Ion) on Light-Degradation of Silk Fabric

It was studied that metal ions affected light-degradation of silk fabric in this paper. The contrast of the weight and the tensile properties of silk fabric treated without or with different concentrations of metal ions (copper sulfate solution and chromium sulfate solution) by different time of light conditions were carried out. The results showed that after the treatment of silk with metal ions solution, the weight gain of the silk fabric increased with increasing the concentration of metal ions solution. There were different changes in the breaking strength of silk fabric treated with different metal ions when subjected to light exposure. In the same light conditions, comparing with the fabric without treatment, the breaking strength of the fabric with copper (ii) ions treatment increased while the breaking strength of the fabric with chromium (iii) ions treatment obviously decreased. Besides, fabric samples with copper ions treatment slowed down the decreasing rate of the breaking strength and fabric samples with chromium ions treatment accelerated the decreasing rate with increasing light exposure time. The results indicated copper (ii) ions had an inhibitory effect on light-degradation of silk fabric, and chromium (iii) ions enhanced light-degradation of silk fabric. Meanwhile, their respective function for fabric increased along with the increment of adsorption values of metal ions on silk fabrics. When being treated with the same concentration of metal ion solution, weight loss of the silk fabric improved and the breaking strength of the fabric decreased with increasing light exposure time, and the two had linear relationship.