Reduction of Cu(II) by photochemically generated phosphonyl radicals to generate Cu(I) as catalyst for atom transfer radical polymerization and azide-alkyne cycloaddition click reactions

The photoinduced electron transfer reactions of acylphosphine oxide type photoinitiators with Cu(II)Cl₂/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine complex for both atom transfer radical polymerization and copper catalyzed azide-alkyne cycloaddition processes is investigated by laser flash photolysis. The photolytically generated phosphonyl radicals are effective in reducing Cu(II) salts to Cu(I) with rate constants of ∼2 × 10⁹ M⁻¹ s⁻¹.     

Effects of specific adsorption of copper (II) ion on charge transfer reaction at the thin film LiMn2O4 electrode/aqueous electrolyte interface

This study investigated the effect of a specific adsorption ion, copper (II) ion, on the kinetics of the charge transfer reaction at a LiMn₂O₄ thin film electrode/aqueous solution (1 mol dm⁻³ LiNO₃) interface. The zeta potential of LiMn₂O₄ particles showed a negative value in 1 × 10⁻² mol dm⁻³ LiNO₃ aqueous solution, while it was measured as positive in the presence of 1 × 10⁻² mol dm⁻³ Cu(NO₃)₂ in the solution. The presence of copper (II) ions in the solution increased the charge transfer resistance, and CV measurement revealed that the lithium insertion/extraction reaction was retarded by the presence of small amount of copper (II) ions. The activation energy for the charge transfer reaction in the solution with Cu(NO₃)₂ was estimated to be 35 kJ mol⁻¹, which was ca. 10 kJ mol⁻¹ larger than that observed in the solution without Cu(NO₃)₂. These results suggest that the interaction between the lithium ion and electrode surface is a factor in the kinetics of charge transfer reaction.     

Chitosan modified with Reactive Blue 2 dye on adsorption equilibrium of Cu(II) and Ni(II) ions

This study aimed at immobilizing Reactive Blue 2 (RB 2) dye in chitosan microspheres through nucleophilic substitution reaction. The adsorbent chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis. This adsorption study was carried out with Cu(II) and Ni(II) ions and indicated a pH dependence, while the maximum adsorption occurred around pH 7.0 and 8.5, respectively. The pseudo second-order kinetic model resulted in the best fit with experimental data obtained from Cu(II) (R = 0.997) and Ni(II) (R = 0.995), also providing a rate constant, k₂, of 4.85 × 10⁻⁴ and 3.81 × 10⁻⁴ g (mg min)⁻¹, respectively, thus suggesting that adsorption rate of metal ions by chitosan-RB 2 depends on the concentration of ions on adsorbent surface, as well as on their concentration at equilibrium. The Langmuir and Freundlich isotherm models were employed in the analysis of the experimental data for the adsorption, in the form of linearized equations. Langmuir model resulted in the best fit for both metals and maximum adsorption was 57.0 mg g⁻¹ (0.90 mmol g⁻¹) for Cu(II) and 11.2 mg g⁻¹ (0.19 mmol g⁻¹) for Ni(II). The Cu(II) and Ni(II) ions were desorbed from chitosan-RB 2 with aqueous solutions of EDTA and H₂SO₄, respectively.     

Synthesis of poly(1,4-naphthylene) bearing crown ether side chain by asymmetric oxidative coupling polymerization

The oxidative coupling polymerization of racemic-, (R)-, and (S)-2,2′,3,3′-tetrahydroxy-1,1′-binaphthyl derivatives bearing a crown ether moiety was carried out in the presence of a Cu(I) or Cu(II) catalyst with various ligands, such as N,N,N′,N′-tetramethylethylenediamine, (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine, (−)-sparteine [(−)Sp], and (S)-(−)-2,2′-isopropylidenebis(4-phenyl-2-oxazoline). Methanol-insoluble poly(binaphthyl crown ether) with a molecular weight up to M_n=4.1×10³ was synthesized in moderate yields. Polymerization using (−)Sp proceeded in an S-selective manner; the polymer with the highest negative specific rotation was obtained with the (S)-monomer. The obtained polymers exhibited characteristic abilities for chiral recognition toward amino acids, such as 2-phenylglycine hydrochloride and 2-phenylglycine methyl ester hydrochloride.     

A nano-structured Ni(II)–ACDA modified gold nanoparticle self-assembled electrode for electrocatalytic oxidation and determination of tryptophan

A nano-structured Ni (II)/ACDA (2-amino-1-cyclopentene-1-dithiocarboxylic acid) film was electrodeposited on a gold nanoparticle–cysteine–gold electrode. The formation of Ni (II)/ACDA film and electrocatalytic oxidation of tryptophan on the surface of the modified electrode were investigated with cyclic voltammetric and chronoamperometric techniques. The hydrodynamic amperometry at rotating modified electrode was used for determination of tryptophan in the range of 0.085–43.0 μmol l⁻¹. The detection limit was found to be 23 nmol l⁻¹. The rate constant, transfer coefficient for the catalytic reaction and the diffusion coefficient of tryptophan in the solution were found to be 9.1 × 10² M⁻¹ S⁻¹, 0.52 and 1.09 × 10⁻⁵ cm² s⁻¹ respectively. It is worth noting that the as formed matrix in our work possesses a 3D porous network structure with a large effective surface area and high catalytic activity and behaves like microelectrode ensembles. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for the analytical purposes.     

Poly(2‐) and (3‐aminobenzoic acids) and their copolymers with aniline: Synthesis,characterization, and properties

Poly(2‐aminobenzoic acid) and poly(3‐aminobenzoic acid) were synthesized by chemical polymerization of the respective monomers with aqueous 1M hydrochloric acid and 0.49M sodium hydroxide, using ammonium persulfate as an oxidizing agent. In addition, polymerization in an acid medium was carried out in the presence of metal ions, such as Cu(II), Ni(II), and Co(II). Poly(2‐aminobenzoic acid‐co‐aniline) and poly(3‐aminobenzoic acid‐co‐aniline) were synthesized by chemical copolymerization of aniline with 2‐ and 3‐aminobenzoic acids, respectively, in aqueous 1M hydrochloric acid. The copolymers were synthesized at several mole fractions of aniline in the feed and characterized by UV–visible and FTIR spectroscopy, the thermal stability, and the electrical conductivity. Metal ions, such as Cu(II), Ni(II), and Co(II), were incorporated into homo‐ and copolymers by the batch method. The percentage of metal ions in the polymers was higher in the copolymers than in the homopolymers. The thermal stability of the copolymers increased as the feed mole fraction of aniline decreased and varied with the incorporation of metal ions in the polymers. The electrical conductivity of the homo‐ and copolymers was measured, which ranged between 10^?3 and 10^?10 S cm^?1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2641–2648, 2003     

Cationic conjugated polyelectrolyte-based fluorometric detection of copper(II) ions in aqueous solution

A series of water-soluble cationic polyfluorene copolymer containing 2,2′-bipyridine moieties (PFP-P_1-3) in the backbone were designed and synthesized as the fluorescent probes for Cu²⁺ ions. In the absence of the Cu²⁺ ion, the PFP-P₂ exhibits strong fluorescence emission in aqueous solution. Upon adding the Cu²⁺ ion, the PFP-P₂ coordinates to Cu²⁺ ions through weak N?Cu interactions, and its fluorescence is efficiently quenched by the Cu²⁺ ion with a Stern-Volmer constant (K_sv) of 1.44 × 10⁷ M⁻¹. The new method has high sensitivity with a detection limit of 20 nM. The minor interference from other heavy metal ions clearly shows that the PFP-P₂ can be used as the Cu²⁺ ion probe with good selectivity.     

Conductometric studies of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) tetrafluoroborates in N,N—dimethylacetamide solutions

Results are reported for the molar conductivities at 25°C of N,N—dimethylacetamide (DMA) solutions of Bu₄NBF₄ and Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) tetrafluoroborates. The limiting molar conductivities of [M(DMA)₆]²⁺ (M  MN, Co, Ni, Cu, Zn) and BF^?₄, as well as association constants for Co(BF₄)₂ in DMA solutions have been calculated. The slight differences between conductometric curves of different metal ions are discussed.     

Synthesis and characterization of highly soluble 9,10-diphenyl-substituted poly(2,6-anthracenevinylene)

We report the synthesis and optoelectronic properties of highly soluble poly(9,10-bis(3′,4′-di(2″-ethylhexyloxy))phenyl)-2,6-anthracenevinylene) (HSM-PAV). The key intermediate for the synthesis of HSM-PAV is 2,6-dimethyl-9,10-dibromoanthracene, and the high solubility of HSM-PAV is from the incorporation of lateral 3,4-di(2-ethylhexyloxy)phenyl moieties into the 9,10-positions of anthracene units. The increase of side alkyloxy groups endows HSM-PAV with higher molecular weight (M_n = 3.2 × 10⁴) and better electroluminescence performances (L_max = 590 cd/m², LE_max = 0.27 cd/A) compared with the poly(2,6-anthracenevinylene) with lateral monoalkyoxy moieties (M_n = 1.9 × 10⁴, L_max = 340 cd/m², LE_max = 0.17 cd/A). The electrical conductivity of doped HSM-PAV film with iodine is 5 × 10⁻² S cm⁻¹ that is several order higher than that of doped 9,10-anthracene-based polymers, further demonstrating that linkage position has a dramatic effect on the optoelectronic properties of anthracene-based conjugated polymers.     

Preparation and characterization of thiocyanate-selective electrodes based on new complexes of copper(II) as neutral carriers

The complexes of hydroxycitronellal (o-aminobenzoic acid) copper(II) (Cu(II)-HXAB) and salicylaldehyde (o-aminobenzoic acid) copper(II) (Cu(II)-SHAB) were used as neutral carriers in PVC-based membrane ion-selective electrodes. The electrode based on Cu(II)-HXAB exhibited near-Nernstian potential response to thiocyanate (SCN⁻) in a linear range of 1.0 × 10^− 6 to 1.0 × 10^− 1 M with a detection limit of 8.5 × 10^− 7 M and a slope of − 57.3 mV/decade in 0.01 M phosphate buffer solution (pH 5.0). The electrode exhibited high selectivity to SCN⁻ over other tested anions with an anti-Hofmeister selectivity sequence. The selectivity behavior might be discussed in terms of UV-Vis spectrum and infrared spectrum. The transfer process of thiocyanate across the membrane interface was investigated by making use of the AC impedance technique. The electrode containing Cu(II)-HXAB could be applied to thiocyanate analysis in waste water with satisfactory results.     

Polyelectrolyte-Cu(II) interactions studied by cyclic voltammetry

SUMMARY The polymer-metal ion interactions were studied by cyclic voltammetry. These were carried out with poly(acrylic acid)-Cu(II) and poly(vinylsulfonic acid)-Cu(II) systems at different pH. At low pH, the polymer was adsorbed on the electrode surface increasing the irreversibility of the Cu²⁺/Cu(s) redox system. At pH 2.7, it was possible to demonstrate that the interaction between Cu(II) and poly(vinylsulfonic acid) is basically electrostatic and with poly(acrylic acid) a complex formation also exists. Received: 5 April 2000/Accepted: 16 August 2000     

Highly salicylate-selective membrane electrode based on a new thiomacrocyclic Schiff base complex of binuclear copper(II) as neutral carrier

New binuclear metallic complexes of thiomacrocyclic Schiff base, 3,9,13,19 -tetraphenyl-6,16-dithione-1,11-dithio-4,5,7,8,14,15,17,18-octaazacycloeicosa-3,8,13,18-tetraene binuclear metal(II) [M(II)₂-TDDOCT] (M = Cu, Co, Ni), were synthesized and their anion response characteristics were investigated. The performances of the electrodes are considerably influenced by the nature of the central metals. The Cu(II) complex-based electrode exhibited a good selectivity to salicylate anion with an anti-Hofmeister selectivity pattern: Sal⁻ > ClO₄⁻ > SCN⁻ > I⁻ > Benzoate > B_r⁻ > Acetate > F⁻ > SO₃²⁻ > NO₂⁻ > Cl⁻ > NO₃⁻ > SO₄²⁻ > H₂PO₄⁻. The electrode had an excellent linear response to Sal⁻ from 9.0 × 10^− 7 to 1.0 × 10^− 1 M with a slope of − 59.3 mV per decade,a detection limit of 5.0 × 10^− 7 M, and a fast response time within 15 s over the entire concentration series in phosphate buffer solutions of pH 5.0 at 25 °C. Spectroscopic techniques and the influence of lipophilic charged additives on the electrode behavior were used to investigate the response mechanism to Sal⁻. The electrode can be applied to the direct determination of salicylate in human urine and pharmaceutical samples and the results obtained are in accord with the results from a standard method.     

Formation, Characterization and Electrical Conductivity of Polycarbosilazane-Cu(II), -Ni(II) and -Cr(III) Chloride Metallopolymers

A series of transition metal-polycarbosilazane complexes have been prepared by the reaction of poly(N,N-bis(dimethylsilyl)ethylenediamine), [–Si(CH₃)₂NHCH₂CH₂NH–] _n , with Cu(II), Ni(II), and Cr(III) chloride. The resulting complexes were characterized by infrared (FT-IR) and UV-visible spectroscopy, magnetic susceptibility measurements, thermogravimetric analysis (TGA), and powder X-ray diffraction (XRD). The average chain-chain spacing in these materials were estimated from XRD data and found to be 6.88, 7.91, 7.09, and 6.33 Å in metal-free, Cu(II)-, Ni(II)-, and Cr(III)-containing polycarbosilazanes, respectively. DC electrical conductivity measurements showed that all these metal-polycarbosilazane complexes exhibit semiconductor behavior while the metal-free matrix is an insulator.     

Simultaneous determination of trace aluminum (III), copper (II) and cadmium (II) in water samples by square-wave adsorptive cathodic stripping voltammetry in the presence of oxine

A validated adsorptive cathodic stripping voltammetry method is described for simultaneous determination of Al(III), Cu(II) and Cd(II) in water samples. In acetate buffer (pH 5) containing 10 μM oxine, these metal ions were determined as oxine complexes following adsorptive accumulation onto the HMDE at −0.05 V versus Ag/AgCl/KCl_s. The best signal to noise ratio was obtained using a square wave of scan increment 10 mV, frequency 120 Hz, and pulse-amplitude 25 mV. Limits of detection as low as 0.020 μg L⁻¹ Al(III), 0.012 μg L⁻¹ Cu(II) and 0.028 μg L⁻¹ Cd(II) were achieved. Interference due to various cations (K(I), Na(I), Mg(II), Ca(II), Mn(II), Fe(III), Bi(III), Sb(III), Se(IV), Pb(II), Zn(II), Ni(II), Co(II)), anions (Cl⁻, NO³⁻, SO₄ ²⁻, PO₄ ³⁻) and ascorbic acid was minimal as the measured signals change by 4% at the maximum. The stripping voltammetry method was successfully applied for simultaneous determination of Al(III), Cu(II) and Cd(II) in tap and natural bottled water samples.     

Electrochemical biosensor based on the interaction between copper(II) complex with 4,5-diazafluorene-9-one and bromine ligands and deoxyribonucleic acid

The copper complex of 4,5-diazafluorene-9-one (dafone) and bromine ligands ([Cu(dafone)₂]Br₂) was prepared and its interaction with double-stranded salmon sperm DNA (dsDNA) in pH 8.0 Britton-Robinson (B-R) buffer solution was studied by electrochemical experiments at the glassy carbon electrode (GCE). It was revealed that Cu(dafone)₂Br₂ could bind with salmon sperm DNA strands mainly by intercalation mode. The binding number of [Cu(dafone)₂]Br₂ for each salmon sperm dsDNA chain and equilibrium constant of the binding reaction were calculated to be 3 and 2.8 × 10¹² L³ mol⁻³, respectively. The Cu(dafone)₂Br₂ was further utilized as a new electrochemical DNA indicator for the detection of human hepatitis B virus (HBV) DNA fragment by differential pulse voltammetry (DPV). The difference of its electrochemical responses occurred between hybridized dsDNA duplex and probe DNA was explored to assess the selectivity of the developed electrochemical DNA biosensor. The constructed electrochemical DNA biosensor achieved a detection limit of 3.18 × 10⁻⁹ mol L⁻¹ for complementary target DNA and also realized a robust stability and good reusability.     

Helical poly(N-propargylamide)s with functional catechol groups: Synthesis and adsorption of metal ions in aqueous solution

A novel type of helical N-propargylamide (PA) copolymer was synthesized by catalytic polymerization of monomer 1 (M1), which provided pendent functional catechol groups, and monomer 2 (M2), which endowed the expected copolymer backbones with helical structures. With [(nbd)Rh⁺B^?(C₆H₅)₄ (nbd = 2,5-norbornadiene)] as catalyst, PA copolymers could be obtained with moderate molecular weights (3800–14,000) in high yields (?96%). The functional catechol groups enhanced the hydrophilicity of the hydrophobic mono-substituted polyacetylenes and aided the helical PA copolymers in showing a considerable adsorbance toward metal ions [Fe(III), Cr(III), Ni(II), Zn(II), Cu(II) and Cu(I)] in aqueous solution. The prepared copolymer in which M1/M2 was 0.1/0.9 [mol/mol, poly(1_0.1-co-2_0.9)] showed the highest adsorption capacity among the examined helical copolymers. In particular, for Fe(III), the maximum adsorption capacity was 186 mg g^?1.     

The kinetics of the Cu/Cu redox couple in deep eutectic solvents

Kinetics of electron transfer of the Cu(I)/Cu(II) redox couple at a platinum electrode has been studied with chronoamperometry, cyclic voltammetry and impedance spectroscopy in a deep eutectic solvent consisting of choline chloride and ethylene glycol. At 25 °C, the reaction was found to be quasi-reversible with a relatively high rate constant k⁰ of 9.5 ± 2 × 10⁻⁴ cm s⁻¹, and a charge transfer coefficient α of 0.25 ± 0.05. Diffusion coefficients for the Cu(I) and Cu(II) complexes were determined to be 2.7 ± 0.1 × 10⁻⁷ and 1.5 ± 0.1 × 10⁻⁷ cm² s⁻¹, respectively. The viscosity of the electrolyte was 41 ± 3 mPa s. The temperature dependency was also investigated. The activation energy of mass transfer was found to be 27.7 ± 1 kJ mol⁻¹ and that of electron transfer 39 ± 7 kJ mol⁻¹. Speciation of the Cu(I) and Cu(II) complexes was determined using UV–VIS spectroscopy, and the prevailing Cu(I) complex was found to be [CuCl₃]²⁻ and that of Cu(II) [CuCl₄]²⁻.     

Stability constants of adipate complexes of copper(II), nickel(II), zinc(II), cobalt(II), uranyl(II) and thorium(IV) determined by electrophoresis

Stability constants of Copper(II), Nickel(II), Cobalt(II), Zinc(II), Uranyl(II) and Thorium(IV) adipates have been determined by paper electrophoresis. Adipic acid (0.005 mol dm^?3) was added to the background electrolyte: 0.1 mol dm^?3 HClO₄. The proportions of (CH₂)₄COOH COO^? and (CH₂)₄C₂O⁼₂ were varied by changing the pH of the electrolyte. These anions yielded the complexes Zn(CH₂)₄COOH COO⁺, Co(CH₂)₄COOH COO⁺, Ni(CH₂)₄COOH COO⁺, Th(CH₂)₄COOH COO³⁺, Th[(CH₂)₄COOH COO]₄, Cu(CH₂)₄ C₂O₄ and UO₂[(CH₂)₄(C₂O₄)]^2?₂, whose stability constants are found to be 10^2.8, 10^2.8, 10^3.2, 10^5.2, 10^15.3, 10^2.7 and 10^11.8 respectively (μ = 0.1, temp. 40°C).     

Neutral Pd(II) and Ni(II) Acetylide Catalysts for the Polymerization of Methyl Methacrylate

Homogenous polymerization of methyl methacrylate using Pd(II)- and Ni(II)-based acetylide complexes as initiators has been investigated. M(PR'₃)₂(CCR)₂ (M=Pd, Ni; R'=PPh₃, Pn-Bu₃; R=Ph, CH₂OH, CH₂OOCCH₃, CH₂OOCPh, CH₂OOCPhOH-o) were found to be a novel type of effective initiators for the polymerization of methyl methacrylate. Among them, Pd(C CPh)₂(PPh₃)₂ (PPP) shows the highest activity in the MMA polymerization and the PMMA obtained is a syndiotactic polymer with high number-average molecular weight (M _n) of 14.1 × 10⁴. Some features and kinetic behavior of MMA polymerization initiated by PPP were studied in detail. The polymerization reaction is first-order with respect to both [PPP] and [MMA]. Radical polymerization mechanism is proposed.     

Crown ether bridged homo- and heterodinuclear copper(II) and nickel(II) cyclidene complexes: Interaction with anions

Homodinuclear (3CuCu, 3NiNi) and heterdionuclear (3CuNi) cyclidene complexes linked by two 1,10-diaza-18-crown-6 ethers were synthesized and their properties characterized. For the 3CuCu in the negative potential range the mixed-valence state Cu^I-Cu^II was observed and the comproportionation constants were determined. The redox potentials of M^II/III showed a good correlation with DN of the solvent. In acetonitrile solution containing 0.1 mol dm⁻³ Bu₄NPF₆ reversible M^II/III redox processes were observed. However, in the presence of stronger ion pairing anions (e.g. BF₄⁻ and ClO₄⁻) the “potential inversion” occurred. Redox potentials of dinuclear complexes were compared with mononuclear cyclidene complexes. The influence of selected anions (Cl⁻ and NO₃⁻) on the redox process M^II/III was studied. The effect of Cl⁻ anion was different for 3CuCu and 3NiNi. In 3CuCu coordination of two chloride anions took place after oxidation of copper centers. In the 3NiNi complex two Cl⁻ anions were coordinated to one of the nickel(II) centers facilitating oxidation, at different potentials, of both nickel(II) cations. The behaviour of heteronuclear complex with Cl⁻ anions was similar to 3NiNi. All dinuclear complexes interacted with NO₃⁻ anions and the observed potential shifts were larger for nickel(II) than for copper(II) cations.