Water-soluble Copper Complexes Research Articles

Catalytic cyclohexane oxidation to KA oil using novel hydrosoluble copper(I) complexes bearing aminophosphine ligands: Water as a selectivity promoter

Reacting the alkylated 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane (PTA), namely (PTA-CH2-C6H4-p-COOH)Br (1) or (PTA-CH2-C6H3-p-OH-m-CHO)Cl (2), with CuBr, CuI or [Cu(CH3CN)4]BF4, under mild conditions using different stoichiometric ratios resulted in the formation of the new water soluble copper complexes [CuBr2(PTA-CH2-C6H4-p-COOH)2]X (X = Br {3a}, I {3b} or BF4 {3c}), [CuBr(PTA-CH2-C6H4-p-COOH)3]Br3 (4) and [CuCl2(PTA-CH2-C6H3-p-OH-m-CHO)2]X (X = I {5a} or Cl {5b}). The compounds were characterized using multinuclear NMR, FTIR, ESI-MS and elemental analysis. The molecular structure of the neutral form of 3 was established by single crystal X-ray diffraction. In a homogeneous aqueous medium, the catalytic activity of the hydrophilic complexes was assessed for the cyclohexane oxidation to the KA oil (a mixture of cyclohexanone and cyclohexanol). The selectivity towards cyclohexanone is controlled by water, increasing with the H2O amount, and becoming higher than that of cyclohexanol for the 25–75% range of water in the solvent composition. Complex 5a exhibited the highest catalytic activity, achieving up to 21% conversion after 4 h at 50 °C using 0.5 mol% of the catalyst. Utilizing a similar loading of 5a, under microwave irradiation, afforded 18% of yield after 1.5 h at 70 °C.

Exploring the Potential of Water-Soluble Cu(II) Complexes with MPA–CdTe Quantum Dots for Photoinduced Electron Transfer

Three water-soluble copper complexes based on the amine/pyridine functionalities were investigated, along with quantum dots, as a catalyst–photosensitizer assembly, respectively, for fundamental understanding of photoinduced electron transfer. Luminescence quenching and lifetime measurements were performed to try and establish the actual process that leads to the quenching, such as electron transfer, energy transfer, or complex formation (static quenching). Cyclic voltammetry and dynamic light scattering experiments were also performed. Irrespective of the similar reduction potentials of the three complexes, very different photoluminescence properties were observed.

Electrocatalytic water oxidation by a water-soluble copper complex with a pentadentate amine-pyridine ligand

A water-soluble copper complex bearing a pentadentate N5 ligand works as an efficient and stable electrocatalyst for the water oxidation reaction in basic aqueous solution.

Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex

AbstractDifferent benzylic compounds were efficiently oxidized to the corresponding ketones with aqueous 70% tert-butyl hydroperoxide (TBHP) and the catalytic system composed of CuCl2.2H2O and 2,2’-biquinoline-4,4’-dicarboxylic acid dipotassium salt (BQC). The catalytic system CuCl2/BQC/TBHP allows obtaining high yields at room temperature under organic solvent-free conditions. The interest of this system lies in its cost effectiveness and its benign nature towards the environment. Benzylic tertbutylperoxy ethers and benzylic alcohols were observed and suggested as the reaction intermediates. Analysis of organic products by atomic absorption did not show any contamination with copper metal. In terms of efficiency, CuCl2/BQC system is comparable or superior to the most of the catalytic systems described in the literature and which are based on toxic organic solvent.

Water‐Soluble Copper Complex Derived from Ligand TETATA Having NNN Donors: Studies on Rapid Degradation of Organic Dyes, Catecholase and Phenoxazinone Synthase Activities

AbstractWater‐soluble copper complex [Cu(TETATA)(Cl2)] (1) derived from tridentate ligand (TETATA) (L=2‐(2‐((2‐((2‐aminoethyl)amino)ethyl)‐ amino)ethyl)isoindoline‐1,3‐dione) having NNN donor, was synthesized, characterized and its molecular structure was determined using X‐ray crystallography. This water soluble copper complex was found to be an efficient catalyst for rapid degradation of organic dyes like orange II, rhodamine B and methylene blue dyes were investigated. This catalyst was also utilised for the oxidation of catechol, giving rise to catecholase activity as well as oxidative coupling of 2‐aminophenol providing phenoxazinone synthase activity. DFT and TD‐DFT calculations were performed to understand the electronic properties of this molecule using B3LYP/LANL2DZ basis set.

Hydrogen production in a neutral aqueous solution with a water-soluble copper complex

A water-soluble polypyridine copper complex Cu(dpp)(ClO4)2 (1, dpp = 2,9-di(pyridin-2-yl)-1,10-Phenanthroline) enables to electrocatalyze H2 generation from neutral phosphate buffer solution at a relatively low overpotential of 520 mV vs. SHE. Sustained proton reduction catalysis occurs at glassy carbon electrode at −1.4 V vs. SHE for 2 h to give H2 with TONs of 734 mol H2 (mol catalyst)−1 cm−2 and 95% Faradaic yield. CVs, UV–Vis spectra, SEM, EDX and Tyndall analysis reveals that 1 has the desired stability and functions as a molecular electrocatalyst under the conditions. Due to the relatively low overpotential and high stability, light-driven hydrogen production based on 1 were also carried out with a TONs of 6 mol H2 (mol catalyst)−1 in an aqueous solution.

A water soluble and fast response fluorescent turn-on copper complex probe for H2S detection in zebra fish

According to the displacement method, herein we reported a water soluble copper complex [Cu(MaT-cyclen)2] as a fluorescent probe for the detection of H2S. For this, 1-((1-((10-methylanthracen-9-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)-1,4,7,10-tetraazacyclododecane (MaT-cyclen) was synthesized first. To improve its solubility in aqueous media, sodium acetate group was introduced into 8-hydroxy-2-quinoline successfully. MaT-cyclen was chelated with Cu(II) to form [Cu(MaT-cyclen)2] complex, which displayed high sensitivity and selectivity for H2S over the other possible competitive substances on the basis of forming CuS. Meanwhile, [Cu(MaT-cyclen)2] displayed rapid response (<1min), well reversibility, lowest detection limit (205nM), and high sensitivity for recognizing H2S in aqueous solution. Furthermore, its potential utility for biological applications was confirmed by fluorescence imaging of H2S in live cells as well as in zebra fish.

Earth-Abundant Copper-Based Bifunctional Electrocatalyst for Both Catalytic Hydrogen Production and Water Oxidation

The production of hydrogen through water splitting via electrolysis/photocatalysis seems a promising and appealing pathway for clean energy conversion and storage. Herein we report for the first time that a series of water-soluble copper complexes can be used as catalyst precursors to generate the copper-based bifunctional catalyst composite for both hydrogen production and water oxidation reactions. Under an applied cathodic potential, a thin catalyst film was grown on a fluorine-doped tin oxide (FTO) electrode, accompanied by the production of a large amount of hydrogen gas bubbles. Scanning electron microscopy shows the presence of nanoparticulate material on the FTO. Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated that the materials consist of amorphous cuprous oxide mixed copper hydroxide (H2–CuCat), which can catalyze water reduction in a copper-free aqueous solution (pH = 9.2) under a low overpotential. Remarkably, under an applied anodic potential, the m...

Synthesis of poly(2,6-dimethyl-1,4-phenylene oxide) derivatives in water using water-soluble copper complex catalyst with natural ligands

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was synthesized by oxidative polymerization of 2,6-dimethylphenol (DMP) using a water-soluble copper complex catalyst under oxygen and with natural ligands in alkaline water. Arginine, guanine, adenine, cytosine, histidine, and folic acid were used as ligands for the copper complex. Arginine performed the best, with a yield of 72%, a number-average molecular weight (Mn) of 4400, and a molecular weight distribution (Mw/Mn) of 1.7. It was then used to optimize reaction conditions. Surfactants, temperature, and sodium hydroxide concentration were varied in copolymerization of DMP and 2-allyl-6-methylphenol (AMP) to produce allyl-containing PPO with 77% yield (Mn = 4500; Mw/Mn = 1.8). The optimum conditions were applied to copolymerization of DMP, AMP, and bisphenol A, leading to dihydroxyl PPO analogs containing thermally cross-linkable allyl groups. The thermal properties of these thermosetting PPOs were studied by differential scanning calorimetry, thermogravimetric analysis, and Fourier-transform infrared spectroscopy.

Catalyzed oxidative polymerization to form poly(2,6-dimethyl-1,4-phenylene oxide) in water using water-soluble copper complex

Simply stirring 2,6-dimethylphenol with a small amount of copper complex catalyst in alkaline water provided a green way to prepare poly(2,6-dimethyl-1,4-phenylene oxide) in water. We have searched for the optimum alkaline-resistant metal catalyst from a series of water-soluble copper complexes. The formed polymer was easily separated as an off-white powder by filtration after salting out.

A New and Highly Efficient Water‐Soluble Copper Complex for the Oxidation of Secondary 1‐Heteroaryl Alcohols by tert‐Butyl Hydroperoxide.

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An unprecedented highly efficient solvent-free oxidation of alkynes to α,β-acetylenic ketones with tert-butyl hydroperoxide catalyzed by water-soluble copper complex

The catalytic system composed of CuCl 2 and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC) was found to be highly efficient for the selective α-oxidation of internal alkynes to the corresponding α,β-acetylenic ketones, with aqueous tert-butyl hydroperoxide under mild conditions. For the first time, full conversions of alkynes were reached with excellent selectivities, and propargylic tert-butylperoxy ethers were observed and suggested as the reaction intermediates. In the case of terminal alkynes, the oxidations are sluggish and low yields ranging from 32% to 40% were obtained.

A new and highly efficient water-soluble copper complex for the oxidation of secondary 1-heteroaryl alcohols by tert-butyl hydroperoxide

The water-soluble copper complex generated in situ from CuCl 2 and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), has been revealed as a highly efficient and selective catalyst for the oxidation of secondary 1-heteroaryl alcohols to the corresponding heteroaromatic ketones with aqueous tert-butyl hydroperoxide, under mild conditions. The catalytic system is compatible with different heterocycles such as pyridines, pyrroles, indoles, thiophens, furans, thiazoles, and imidazoles.

Solvent-free oxidation of alcohols by t-butyl hydroperoxide catalyzed by water-soluble copper complex

The catalytic system composed of CuCl 2 and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), was found to be highly efficient for the selective oxidation of secondary benzylic, allylic and propargylic alcohols to the corresponding ketones, with aqueous t-butyl hydroperoxide under phase-transfer catalysis conditions. The catalytic system is stable and can be recycled and reused several times without loss of activity.

Use of Diastereomeric Interactions To Probe the Inplane Attachment of Water-Soluble Molecules to the Polar Head Groups of Langmuir Films of Cu−α-Amino Acid Complexes

To provide more direct information on the role played by “tailor-made” auxiliary molecules in the early stages of crystal nucleation, the interplay between clusters of polar headgroups of monolayers of the copper complexes S−Cu−S‘ and S−Cu−R‘ and water-soluble copper complexes S‘−Cu−S‘ and R‘−Cu−R‘ were investigated [where S represents enantiomerically pure (S)-palmitoyl-Nε-lysine, and S‘ and R‘ represent chiral resolved (S) and (R) forms of alanine, serine, or valine]. The different monolayers were formed by spreading the amphiphilic (R) or (S) α-amino acid on an aqueous solution of copper acetate followed by injection of the water-soluble (S‘) or (R‘) α-amino acid into the subphase. The surface pressure−molecular area isotherms of the Langmuir monolayers of the two type of complexes (S−Cu−S‘ and S−Cu−R‘) are different, the former being substantially more expanded. The polar headgroups of the S−Cu−S‘ and of the S−Cu−R‘ monolayers transferred onto a solid support assume a trans and cis configuration, respectively, according to comparative X-ray photoelectron spectroscopy (XPS) studies with appropriate cis and trans three-dimensional (3-D) α-amino acid Cu complexes. A grazing incidence X-ray diffraction (GIXD) analysis demonstrated that the S−Cu−S‘ and S−Cu−R‘ monolayers have different 2-D crystal structures, in keeping with the XPS results. A model is presented suggesting that the water-soluble S‘−Cu−S‘ copper complexes are enantioselectively bound to the periphery of the domains of the cis S−Cu−S‘ monolayers, but not to the domains of the trans S−Cu−R‘ monolayers. By symmetry, the same principal holds for the monolayers and water soluble copper complexes of α-amino acids of the opposite handedness.