Kinetics of the metal exchange reaction of a Cu(II)-poly(vinyl alcohol) complex with Zn(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid in aqueous solution

The kinetics of the metal exchange reaction between Cu(II)-poly(vinyl alcohol) [Cu(II)-PVA] and Zn(II)-ethylenediamine-N,N,N,N-tetraacetic acid [Zn(II)-EDTA] has been studied by mixing both solutions in a spectrophotometer at pH 10.0 to 11.0, ionic strength =0.10(KNO₃), and 15 to 35°C. The reaction is initiated by the formation of unstable Cu(II)-H-PVA through attack of H⁺ ion on the Cu(II)-PVA complex, and both reactions, ligand exchange and metal exchange, proceed simultaneously. The metal exchange step may be rate determining. The rate equation and rate constants of this reaction were determined as follows: –d[Cu(II)-PVA]/dt=k _0(H)[PVA^–][Cu(II)-PVA] [Zn(II)-EDTA], wherek _0(H)=k ₁+(k₂+k₃)[H⁺],k ₁=5.98±1.64M ^–1 s^–1, andk ₂+k ₃=k₂ K _Cu(II)-H-PVA ^–H +k₃ K _Zn(II)-EDTA ^H =(5.91±0.89)×10⁷ M ^–2 s^–1.     

Kinetics of the metal exchange reaction of a Cu(II)-poly(vinyl alcohol) complex with Zn(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid in aqueous solution

The kinetics of the metal exchange reaction between Cu(II)-poly(vinyl alcohol) [Cu(II)-PVA] and Zn(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid [Zn(II)-EDTA] has been studied by mixing both solutions in a spectrophotometer at pH 10.0 to 11.0, ionic strength μ=0.10(KNO₃), and 15 to 35°C. The reaction is initiated by the formation of unstable Cu(II)-H-PVA through attack of H⁺ ion on the Cu(II)-PVA complex, and both reactions, ligand exchange and metal exchange, proceed simultaneously. The metal exchange step may be rate determining. The rate equation and rate constants of this reaction were determined as follows: ?d[Cu(II)-PVA]/dt=k _0(H)[PVA^?][Cu(II)-PVA] [Zn(II)-EDTA], wherek _0(H)=k ₁+(k′₂+k′₃)[H⁺],k ₁=5.98±1.64M ^?1 s^?1, andk ₂+k ₃=k′₂ K _Cu(II)-H-PVA ^?H +k′₃ K _Zn(II)-EDTA ^H =(5.91±0.89)×10⁷ M ^?2 s^?1.     

The synthesis, structure, and magnetic properties of a novel copper(II) cluster with H-bonding directed 3D-structure comprised of interconnected double-stranded ladders

Reaction between 2,6-diformyl-4-methylphenol (DFMP) and tris(hydroxymethyl)aminomethane (THMAM) with copper(II) acetate and sodium azide formed the antiferromagnetically coupled, polymeric copper(II) coordination cluster {[(H₅L)Cu₂(μ-N₃)]₂[Cu(N₃)₄]·2CH₃OH}_n (1), with a novel double-stranded ladder like structure in which [Cu(N₃)₄]²⁻ anions link single-chains comprised of dinuclear subunits, forming a 3D-structure of interconnected ladders through H-bonding. The 3D-structure is the result of coordinatively driven and hydrogen-bonding directed self-assembly.     

Preparation of Cu(II)‐chelated poly(vinyl alcohol) nanofibrous membranes for catalase immobilization

Poly(vinyl alcohol) (PVA) nanofibers were formed by electrospinning. Metal chelated nanofibrous membranes were prepared by reaction between Cu(II) solution and nanofibers, and which were used as the matrix for catalases immobilization. The constants of Cu(II) adsorption and properties of immobilized catalases were studied in this work. The Cu(II) concentration was determined by atomic absorption spectrophotometer (AAS), the immobilized enzymes were confirmed by the Fourier transform infrared spectroscopy (FTIR), and the amounts of immobilized enzymes were determined by the method of Bradford on an ultraviolet spectrophotometer (UV). Adsorption of Cu(II) onto PVA nanofibers was studied by the Langmuir isothermal adsorption model. The maximum amount of coordinated Cu(II) (q_m) was 2.1 mmol g⁻¹ (dry fiber), and the binding constant (K_l) was 0.1166 L mmol⁻¹. The immobilized catalases showed better resistance to pH and temperature inactivation than that of free form, and the thermal and storage stabilities of immobilized catalases were higher than that of free catalases. Kinetic parameters were analyzed for both immobilized and free catalases. The value of V_max (8425.8 μmol mg⁻¹) for the immobilized catalases was smaller than that of the free catalases (10153.6 μmol mg⁻¹), while the K_m for the immobilized catalases were larger. It was also found that the immobilized catalases had a high affinity with substrate, which demonstrated that the potential of PVA‐Cu(II) chelated nanofibrous membranes applied to enzyme immobilization and biosensors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Formation of an unusual copper(II) complex from the degradation of a novel tricopper(II) carbohydrazone complex

An unusual copper(II) complex [Cu(L^1a)₂Cl₂] CH₃OH·H₂O·H₃O⁺Cl⁻ (1a) was isolated from a solution of a novel tricopper(II) complex [Cu₃(HL¹)Cl₂]Cl₃·2H₂O (1) in methanol, where L^1a is 3-(2-pyridyl)triazolo[1,5-a]-pyridine, and characterized with single crystal X-ray diffraction study. The tricopper(II) complex of potential ligand 1,5-bis(di-2-pyridyl ketone) carbohydrazone (H₂L¹) was synthesized and physico-chemically characterized, while the formation of the complex 1a was followed by time-dependant monitoring of the UV–visible spectra, which reveals degradation of ligand backbone as intensity loss of bands corresponding to O → Cu(II) charge transfer.     

Unique direct synthesis of cyanide-bridged Fe2Cu2 molecular squares by destruction of sodium nitroprusside

The one-pot reaction of copper powder, sodium nitroprusside, ammonium thiocyanate and 2,2′-bipyridine (bpy) in acetonitrile solution at ambient conditions of air and water yields the novel heterometallic [Fe₂Cu₂(bpy)₆(μ-CN)₄(NCS)₂]₂[Fe(CN)₅(NO)](NCS)₂·5H₂O complex 1, which has been structurally and magnetically characterized. The most prominent feature of this complex is the unique tetranuclear squares comprised [Cu(bpy)NCS]⁺ and [Fe(bpy)₂]²⁺ corners with CN edges. The CuCu and FeFe separations are 6.72 and 7.73 Å, respectively. The variable-temperature magnetic susceptibility study revealed that a very weak antiferromagnetic coupling is active between Cu(II) centers (J_CuCu = −0.37 cm⁻¹).     

A novel one-dimensional nickel(II) complex with a hydrogen-bond-link

A novel compound [Ni(L)(H₂O)₂]_0.5[Ni(L)(WO₄)₂]_0.5·4H₂O (1) (L=3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) has been structurally and magnetically characterized. The nickel(II) ions are shown to be in distorted octahedral environments with secondary amines of macrocycles in which two trans water molecules and two trans tungstate ions are assembled around each metal center. Two nickel(II) complexes are connected into a one-dimensional chain via hydrogen bonds. The magnetic susceptibility measurement for 1 indicates weak antiferromagnetic interaction (J=−1.01(2) cm⁻¹; H=−JΣS_i·S_i+1) between the S=1 nickel(II) paramagnetic centers.     

Reactions of bis(3-aminopropyl)amine with formaldehyde in the presence of a metal ion: Preparation of a metal-free macropolycycle and a dinuclear copper(II) complex

The reaction of bis(3-aminopropyl)amine with excess formaldehyde in the presence of Ni²⁺ ion produces the macropentacyclic compound L¹(ClO₄)₂ (1) L¹ = 1,3,7,11,13,17- hexaazapentacyclo[15.3.1.1^3.7.1^7.13.1^13.17]tetracosane). The dinuclear complex [Cu₂(L²)₂(H₂O)₂](ClO₄)₂ (2) (HL¹ = 1-(3-aminopropyl)-3-(hydroxymethyl)-1,3-diazacyclohexane) as well as 1 can be prepared by the condensation reaction in the presence of Cu²⁺ ion. Interestingly, 2 · 2H₂O exhibits uncommon magnetic behavior.     

Structural Pitstops and Turnoffs on the Way to the Birefringent 2-D Layer Structure $$\{\hbox{(tmeda)M[Hg(CN)}_{2}]_{2}\}[\hbox{HgCl}_{4}]$$ (M=Cu,Ni)

The reaction of N,N,N′,N′-tetramethylethylenediamine (tmeda) and NiCl₂ with the soft, Lewis acidic Hg(CN)₂ and HgCl₂ in ethanol formed the 2-D layer structure {(tmeda)Ni[Hg(CN)₂]₂}[HgCl₄] (1), isostructural to the Cu(II) analogue. Complex 1 crystallizes in the tetragonal, non-centric m space group and contains a 2-D cationic layer of {(tmeda)Ni[Hg(CN)₂]₂}²⁺ units in which the six-coordinate Ni(II) centres are bridged by four Hg(CN)₂ groups and capped by a tmeda ligand. This array is interspersed with a layer of [HgCl₄]²⁻ anions, which form bridging Hg–Cl bonds with the Hg(CN)₂ units. The formation of 1 is very sensitive to reaction conditions; the addition of water to the mixture yields the related “structural pitstop” 2-D array {(tmeda)Ni(H₂O)[Hg(CN)₂]}{[Hg(CN)Cl]₂Cl₂}·H₂O (2), in which the halide migration among Hg(II) centres is incomplete. The larger zero-field splitting D-values of 6.91(1) cm⁻¹ for 1 vs. 2.85(4) cm⁻¹ for 2 indicate that some weak antiferromagnetic interactions are likely present in 1. The reaction of tmeda/Cu(ClO₄)₂·6H₂O with Hg(CN)₂ yields [Cu(tmeda)(μ-OH)(ClO₄)]₂[Hg(CN)₂(H₂O)₂][Hg(CN)₂] (3) which is composed of [Cu(tmeda)(μ-OH)(ClO₄)]₂ dimers in which the anions cis-bridge the copper(II) centres in the axial positions as well as bind to two adjacent Hg(CN)₂ moieties; the perchlorate anion is acting as a rare η⁴–μ₄–ClO₄ ligand. N-cyano interactions also exist between the Hg(II) centres; overall, a 2-D corrugated sheet structure which stacks via Cl–O–Hg bridges to yield a 3-D array is formed. The χ_M T value for 3 decreases with decreasing temperature; a maximum in χ_M vs. T at 20 K is also observed. This is consistent with antiferromagnetic interactions within the copper(II) dimer, which were fit with the Bleaney-Bowers model to yield J=−23.1(1) cm⁻¹, g=2.113(5) and a paramagnetic impurity P=0.017(1).Special Issue to honour Professor Richard J. Puddephatt     

Tracking the Transformation Process of a Pair of Zn(II) Coordination Clusters: Crystallography and Mass Spectrometry

Two zinc clusters Zn₄(H₃L)₄(NO₃)₄?5H₂O ( Zn₄ , H₄L=(1,2‐bis(1H‐benzo[d]imidazol‐2‐yl)ethane‐1,2‐diol) and [Zn₅(H₂L′)₆](NO₃)₄]?8H₂O?2CH₃OH ( Zn₅ , H₃L′=(1,2‐bis(benzo[d] imidazol‐2‐yl)‐ethenol) have been obtained by the reaction of Zn(NO₃)₂?6H₂O with H₄L at 80 °C or 140 °C under solvothermal condition. Powder X‐ray Diffraction (PXRD) of precipitate and Electrospray Ionization Mass Spectrometry (ESI‐MS) of reaction solution revealed the existence of transformation behavior from Zn₄ to Zn₅ by increasing the temperature from 80 °C to 140 °C, or directly heating Zn₄ at 140 °C via solvothermal reaction. Here we proposed a possible mechanism involves split process of Zn₄ and reassembly to form Zn_{5 .} ESI‐MS for single crystals revealed [Zn₄(H₃L)₄?3H]⁺ splits to [Zn(H₃L)]⁺ via [Zn₂(H₃L)₂?H]⁺. Time dependent ESI‐MS of reaction solution revealed the [Zn(H₂L′)]⁺→[Zn₂(H₂L′)₂?H]⁺→[Zn₅(H₂L′)₆?H]³⁺ stepwise assembly. It also has been captured the in situ reaction mainly occurs in the step of [Zn(H₃L)]⁺ to [Zn(H₂L′)]⁺.     

An unexpected sulfinate–sulfonate mixed coordination polymer of copper(II)

By reaction of copper nitrate trihydrate and 2,2′-dipyridyldisulfide in both aerobic and anaerobic conditions, the mixed [{Cu(2-pySO₂)₂}_n]–[{Cu(2-pySO₃)₂}_n] coordination polymer of copper(II) (1) has been synthesized. The X-ray diffraction analysis indicates that complex 1 exhibits an infinite one-dimensional polymeric chain consisting of [Cu(C₅H₄N)₂] building units connected by SO₂/SO₃ groups. The atom which has been labelled O3 is only present in 60% of the molecules. Complex 1 exhibits a very weak ferrogmagnetic spin coupling (zJ = +0.40 cm⁻¹).     

THIOCYANATE-ASSISTED SOLID PHASE ENRICHMENT OF Cu(II) USING PYRIDINE DERIVATIVE WITH X-RAY CRYSTALLOGRAPHIC EVIDENCE

Equimolar mixture of pyridine-2,6-dimethanol (PDM), and thiocyanate ion immobilized on silica serves as an efficient sorbent for selective retention of Cu(II) from other associated metal ions at µg g^?1 level. The maximum sorption capacity for Cu(II) was found as 2.44 mmol g^?1 at pH 6.0. The sorbed Cu(II) was completely eluted with 3 mol L^?1 HNO₃ and measured with a flame atomic absorption spectrometer (FAAS). The structure of the extracted Cu(II) complex was confirmed by single-crystal X-ray structure analysis and Fourier transform-infrared (FT-IR) spectroscopy. Thermogravimetric analysis (TGA) of the isolated Cu(II) complex was performed to determine its thermal stability at the extraction temperature. The three sigma detection limit (N = 15) of the method is 0.6 µ g mL^?1 with a relative standard deviation (RSD) of 0.1% (N = 15). Pre-concentration factor of the method is 133. Slight interference from Mn²⁺ ion was eliminated by prior oxidation with potassium periodate. The developed method was tested for trace level separation and estimation of Cu(II) in certified reference materials and environmental samples.

[Supplementary materials are available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resources: two tables providing details of the bond lengths and bond angles of the Cu(II) complex.]     

Photochemical reductive elimination of [PtIV(NH3)4(NH2)Cl]2 +: Photogeneration of hydrazine

When [Pt^IV(NH₃)₅Cl]^3 + is deprotonated the complex [Pt^IV(NH₃)₄(NH₂)Cl]^2 + is formed. Upon NH₂⁻ → Pt^IV LMCT excitation (λ_irr > 250 nm) a reductive elimination takes place: [Pt^IV(NH₃)₄(NH₂)Cl]^2 + → [Pt^II(NH₃)₃Cl]⁺ + N₂H₄ + H⁺. Since Pt(II) ammine complexes can be reoxidized to Pt(IV) by H₂O₂ it is suggested that in a cyclic process the overall reaction could proceed according to the equation: 2 NH₃ + H₂O₂ → N₂H₄ + 2 H₂O.     

Reversible photoreaction of C60-containing poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was reacted with strong base NaH to convert its pendant hydroxy to oxy anions, followed with nucleophilic addition to buckminsterfullerene-C₆₀. The resulted PVA(C60−Na⁺)_n products were then converted to PVA(C₆₀H)_n by stirring with a strong acid cation exchanger of the H⁺ form. The reduced viscosities of PVA(C₆₀H)_n decreases with amount of C₆₀, and are between 0.38 and 0.66 dL/g compared to 1.97 dL/g of the original PVA. Repeated photocrosslinking under 300 nm light and photocleavage under 254 nm light of these C₆₀-containing PVAs were investigated in DMSO by tracing their UV absorption variations at 325 nm (maximum absorption of C₆₀H). It is confirmed that both PVA(C₆₀H)_n exhibit excellent reversibility at least under the observed three cycles. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 605–611, 1998     

Ammonium tris-oxalatoferrate(III) as a source of metalloligand in direct synthesis of Cu/Fe coordination polymer

It has been shown that one-pot reaction of copper powder, ammonium tris-oxalatoferrate(III) (NH₄)₃[Fe(C₂O₄)₃]·3H₂O as a source of metalloligand, and ethylenediamine (en) leads to the formation of heterobimetallic complex (NH₄)[Cu(en)₂Fe(C₂O₄)₃]?2dmso (1). This complex has been characterised by elemental analysis, IR spectroscopy and single crystal X-ray crystallography. Crystal structure analysis reveals that 1 consists of [Cu(en)₂Fe(C₂O₄)₃]^? anionic chains with regularly alternated [Cu(en)₂]²⁺ and [Fe(C₂O₄)₃]^3? moieties. Magnetic susceptibility measurements indicate absence of a significant exchange interaction between the metal units. The polycrystalline X-band EPR spectrum of 1 exhibits broad line characteristic of Fe(III) centers, whereas the signals observed in EPR spectrum of frozen dmf solution of 1 are distinctly associated with zero field splitting in the spin states of rhombically distorted Fe(III) centers, non interacting with Cu(II) centers.     

New coordination polymers. III: Oxidation of poly(vinyl alcohol) by permanganate ion in alkaline solutions. Kinetics and mechanism of formation of intermediate complex with a spectrophotometric detection of manganate(vi) transient species

The kinetics of formation of the [PVA. Mn^VIO] intermediate complex have been measured by the conventional spectrophotometric technique. The rate of formation of the complex was found to be given by the expression d[Complex]/dt = k₁[MnO-₄][PVA^?]. The results showed that the rate of formation is dependent on the base concentration. A first-order reaction in permanganate and fractional order with respect to the poly(vinyl alcohol) (PVA) concentration were observed. The activation parameters have been evaluated and a tentative reaction mechanism has been suggested.     

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.     

The Effect of the Synthetic Conditions on the Deposition and Distribution of Copper Complexes on Polymer Supports

The influence of conditions (e.g., ratios of components, temperature etc.) on the reaction of Cu(OCOCH₃)₂·2H₂O with polyethylene grafted-polyacrylic on the amount of the metal and the composition of the immobilized Cu(II) complexes was studied. The concentration dependence obeys the Langmuir law. Analysis of the data leads to an evaluation of the stability constant for the Cu(II) complexes (K=300 l/mole at 333 K). The constant corresponds to a Cu(II) fixation value, k=0.35 mole/l (22.22 mg Cu(II)/g). The multistage fixation mechanism for Cu(II) complex formation was demonstrated by the marked atom technique. Cu(II) is fixed by one carboxylate group (to 16 mol% of the supported Cu(II), K ₁=16×10^–2 mole/g) and by two carboxylate groups (K ₂=2.54×10^–3 mole/g) of the grafted ligands. The PE-gr-PAA–Cu(II) system mimics the situation-insoluble support-soluble functional polymer covering and realizes the advantages of both the soluble and the three-dimensional crosslinked polymer. Steady-state magnetic susceptibility measurements and ESR spectroscopy were used to study the distribution of cupric ion attached to a polyethylene-grafted poly(acrylic acid) support. The existence of three types of cupric ion complexes was demonstrated: (1) isolated complexes, (2) complexes bonded by dipole–dipole interactions, and (3) clusters with strong exchange interactions. The mean distances between the isolated ions (¯r22–15 Å) and between the dipole–bound complexes (¯r _agreg7 Å) were estimated. The results obtained were compared to the data for other immobilized catalysts. Preliminary results on the fixation of bimetallic Cu(II) and Pd(II) complexes to the polymers as well as on their distributions were obtained.