Sulfoethylated polyethylenimine: synthesis in gel and sorption properties

Using the gel synthesis approach of polymer-analogous transformations, N-sulfoethylation of polyethylenimine was carried out by treating the polymer with sodium vinyl sulfonate. The compositions and structures of the products were characterized by elemental analysis, FT-IR spectroscopy, and ¹H NMR spectroscopy. At pH 3.0–4.5 sulfoethylated polyethylenimine can selectively extract Ag^I and Cu^II from an ammonia—acetate buffer solution in the presence of a series of transition and alkaline-earth metals. At pH > 6.5 the sorbent can be used for the group extraction of a number of transition metal ions. The structural feature of the obtained derivative eliminates the selectivity of sorption of Ag^I ions compared to Cu^II ions, which has previously been revealed for the sulfoethylated derivatives of chitosan and polyaminostyrene.

     

Sorbents based on N-(2-carboxyethyl)chitosan cross-linked by nanosecond electron beams

Methods for the synthesis of new chelating chitosan derivatives containing 2-carboxyethyl groups were developed. Their macromolecules were cross-linked by the irradiation with a nanosecond electron beam, which gave for the first time sorbents with a high sorption capacity for Cu^II ions. The maximum sorption capacity, which is achieved in the pH range 6.5–7.2. and the Langmuir adsorption constant of Cu²⁺ ions on the sorbent with the degree of substitution 0.91 are 1.37 mmol g^?1 and 152.51 L mol^?1, respectively. The structures of the formed complexes in the sorbent phase were characterized by ESR spectroscopy.     

A kinetic study of the oxidation of hydroxamic acids by compounds I and II of horseradish peroxidase: Effect of transition metal ions

Abstract

Oxidation of hydroxamic acids (HXs) generates HNO, and it is not clear whether it is formed also in the presence of metal ions. The kinetics of the oxidation of HXs, such as acetohydroxamic acid, suberohydroxamic acid, and suberoylanilide hydroxamic acid (SAHA), by compounds I and II of horseradish peroxidase (HRP) at pH 7.0 and 25?°C have been studied using rapid-mixing stopped-flow. The kinetics of these reactions were compared to those observed in the presence of Cu(ClO₄)₂, NiSO₄, or ZnSO₄. The rates decrease upon increasing [Cu^II] at constant [HXs], and no oxidation of HX occurs when [HX]/[Cu^II] ≈ 2, implying that HX oxidation in the presence of Cu^II proceeds through the free ligand since the predominant complex is CuX₂. In the case of Ni^II, the oxidation rate decreases upon increasing the ratio [Ni^II]/[HX] beyond 1, where the predominant complex is Ni^IIX⁺, implying that its oxidation is feasible. The effect of Zn^II could be studied only on the rate of HXs oxidation by compound II demonstrating similar behavior to that of Ni^II. HXs were also oxidized catalytically by HRP/H₂O₂ at pH 7.0, demonstrating that metal ions facilitate the formation of HNO while hardly affecting its yield and the extent of HX oxidation.     

Chitin-based magnetic composite for the removal of contaminating substances from aqueous media

A method of obtaining multipurpose magnetic chitin, which combines the magnetic properties of magnetite and the adsorption properties of polysaccharide, was proposed. The possibility of using chitin-(CT) and chitosan (CS)-containing magnetic composites for the adsorption of inorganic ions Co^II and Cr^VI and organic substances (2- and 4-nitrophenols) from aqueous media was analyzed. It was shown that the adsorption capacity of magnetic chitin with respect to Co^II and Cr^VI ions reached 41 mg g^?1 and 15 mg g^?1, respectively. The maximum adsorption capacity for 4-nitrophenol (19 mg g^?1 per CT-containing magnetic composite or 56 mg g^?1 per chitin component) was about three times higher than for 2-nitrophenol. The obtained adsorbent Fe₃O₄/CT is environmentally friendly and reusable.

     

New Mechanistic Insight into Stepwise Metal‐Center Exchange in a Metal–Organic Framework Based on Asymmetric Zn4 Clusters

Herein, a mechanism of stepwise metal‐center exchange for a specific metal–organic framework, namely, [Zn₄(dcpp)₂(DMF)₃(H₂O)₂]_n (H₄dcpp=4,5‐bis(4′‐carboxylphenyl)phthalic acid), is disclosed for the first time. The coordination stabilities between the central metal atoms and the ligands as well as the coordination geometry are considered to be dominant factors in this stepwise exchange mechanism. A new magnetic analytical method and a theoretical model confirmed that the exchange mechanism is reasonable. When the metathesis reaction occurs between Cu^II ions and framework Zn^II ions, the magnetic exchange interaction of each pair of Cu^II centers gradually strengthens with increasing amount of framework Cu^II ions. By analyzing the changes of coupling constants in the Cu‐exchanged products, it was deduced that Zn4 and Zn3 are initially replaced, and then Zn1 and Zn2 are replaced later. The theoretical calculation further verified that Zn4 is replaced first, Zn3 next, then Zn1 and Zn2 last, and the coordination stability dominates the Cu/Zn exchange process. For the Ni/Zn and Co/Zn exchange processes, besides the coordination stability, the preferred coordination geometry was also considered in the stepwise‐exchange behavior. As Ni^II and Co^II ions especially favor octahedral coordination geometry in oxygen‐ligand fields, Ni^II ions and Co^II ions could only selectively exchange with the octahedral Zn^II ions, as was also confirmed by the experimental results. The stepwise metal‐exchange process occurs in a single crystal‐to‐single crystal fashion.     

Structural studies on cadmium(II), cobalt(II), copper(II), nickel(II) and zinc(II) complexes of 1-malonyl-bis(4-phenylthiosemicarbazide)

Summary Several new complexes of the title ligand (H₂MPTS) with Co^II, Ni^II, Cu^II, and Cd^II have been prepared. Structural assignments of the complexes have been made based on elemental analysis, molar conductivity, magnetic moment and spectral (i.r.,¹H n.m.r., reflectance) studies. The compounds are non-conductors in dimethylsulphoxide. The neutral molecule is coordinated to the metal(II) sulphate as a bidentate ligandvia the two carbonyl groups. The ligand reacts with the metal(II) chlorides with the liberation of two hydrogen ions, behaving as a bianionic quadridentate (NONO) donor. Enolization is confirmed by the pH-titration of H₂ MPTS and its metal(II) complexes against NaOH. A distorted octahedral structure is proposed for the Cu^II complex, while a square planar structure is suggested for both Co^II and Ni^II complexes. The stoichiometry of the complexes formed in EtOH and buffer solutions, their apparent formation constants and the ranges for obedience to Beer's law are reported for Co^II, Ni^II and Cu^II ions. The ligand pK values are calculated. The antimicrobial activity of H₂ MPTS and its Co^II, Ni^II, Cu^II and Mn^II complexes is demonstrated.     

Structural aspects of a trimetallic CuII derivative: cytotoxicity and anti-proliferative activity on human cancer cell lines

A trimetallic Cu^II derivative, [Cu₃(L)₂(CF₃COO)₂] (1) (where H₂L = N,N′-bis(salicylidene)-1,3-propanediamine), was prepared and characterized. In 1, the two terminal Cu^II ions are linked to the central Cu^II by trifluoroacetato and doubly bridging phenoxido. Both the square-pyramidal and octahedral geometries are observed among two different Cu^II centers in the linear arrangement of the trimetallic unit. Compound 1 is characterized by IR and UV-Vis spectra. Compound 1 has high cytotoxic activity in breast adenocarcinoma (MCF-7), colorectal carcinoma (HCT116) and particularly, in ovarian carcinoma (A2780) cell line compared to a lung adenocarcinoma cell line. The IC₅₀ in A2780 cells is 25 times lower than the respective value for normal human primary fibroblasts demonstrating 1 has higher cytotoxicity towards cancer cells. Additionally, combination of DOX with 1 induces a higher loss of HCT116 cell viability compared with each drug alone.     

Syntheses,Structures and Spectral Properties of Mononuclear CuII and Dimeric ZnII Complexes Based on an Asymmetric Salamo‐type N2O2 Ligand

The asymmetric Salamo‐type N₂O₂ ligand H₂L and its corresponding Cu^II and Zn^II complexes [CuL] and [{ZnL}₂]·2CH₃CN were synthesized and structurally characterized. Crystallographic data of the Cu^II complex revealed that the Cu^II ion is tetracoordinate with a slightly distorted square planar arrangement forming a 2D supramolecular plane structure by hydrogen bonding and π···π stacking interactions. In the Zn^II complex, the Zn^II ions are pentacoordinate in N₂O₂ tetradentate fashion and intermolecular contacts between Zn^II and oxygen atoms result in a head‐to‐tail dimer. The Zn^II ions were found to have slightly distorted square pyramidal and trigonal bipyramidal arrangements, respectively. Hydrogen bonding interactions stabilized the Zn^II complex to facilitate self‐assembly to a 1D linear chain. The Cu^II and Zn^II complexes show intense photoluminescence with maximum emissions at approx. 426 and 411 nm upon excitation at 360 and 350 nm, respectively.     

Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu‐SSZ‐13

Operando X‐ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu‐exchanged SSZ‐13. Catalysts prepared to contain only isolated, exchanged Cu^II ions evidence both Cu^II and Cu^I ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH₃ together are necessary for Cu^II reduction to Cu^I. DFT calculations show that NO‐assisted NH₃ dissociation is both energetically favorable and accounts for the observed Cu^II reduction. The calculations predict in situ generation of Brønsted sites proximal to Cu^I upon reduction, which we quantify in separate titration experiments. Both NO and O₂ are necessary for oxidation of Cu^I to Cu^II, which DFT suggests to occur by a NO₂ intermediate. Reaction of Cu‐bound NO₂ with proximal NH₄⁺ completes the catalytic cycle. N₂ is produced in both reduction and oxidation half‐cycles.     

High-dimensional mixed-valence copper cyanide complexes: Syntheses,structural characterizations and magnetism

Reactions of CuCl₂ with different CN complexes in presence of a neutral ancillary ligand lead to two novel mixed-valence Cu complexes [Cu^II(bpy)Cu^I(CN)₃]_n, 1 (bpy = 2,2′-bipyridine) and {[Cu^II(tn)₂][Cu^I₄(CN)₆]}_n2 (tn = 1,3-diaminopropane). For compound 1, the asymmetric unit involves two Cu ions Cu1 and Cu2 (Cu^I and Cu^II centres, respectively) which strongly differ in their environments. The Cu1 ion presents a CuC₄ pseudo-tetrahedral geometry, while the Cu2 ion presents a CuN₅ slightly distorted square-pyramidal geometry. The extended structure of 1 is generated by three cyano ligands which differ in their coordination modes. One CN group has a μ₃ coordination mode and bridges two Cu^I and one Cu^II ion, while the two other CN groups act as μ₂ bridges leading to a sophisticated 3-D structure. As for 1, the asymmetric unit of 2 involves three crystallographically different Cu ions (Cu1A and Cu1B, presumably Cu^I centres, and Cu2 presumably Cu^II centres). The Cu2 ion presents centrosymmetric CuN₄ coordination environments involving four nitrogen atoms from two bidentate tn ligands; while the Cu1A and Cu1B ions are three coordinated to cyano groups. The structure can be described as formed by 18-membered “[Cu^I(CN)]₆” planar metallocycles that are connected to their six neighbors to generate 2-D sheets; these sheets stack forming infinite hexagonal channels in which the [Cu(tn)₂]²⁺ units are located. Magnetic measurements show an unexpected weak ferromagnetic coupling (θ = 0.239(1) K) of the Cu^II ions through the long and “a priori diamagnetic” –NC–Cu^I–CN– bridges in compound 1 and an essentially paramagnetic behavior in compound 2.     

Complexation of late transition metal(II) ions (M = Co,Ni, Cu,and Zn) by a macrocyclic thiacrown ether studied by means of electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI‐MS) is used to probe the metal‐binding selectivity of a macrocyclic thiacrown ether (C₄₄H₃₂S₂₀) towards Co^II, Ni^II, Cu^II, and Zn^II. In homogeneous 1:1 v/v methanol/dichloromethane solutions, it is found that the thia ligand very selectively binds traces of copper even in the presence of an excess of the other metal ions. The large selectivity is ascribed to the redox‐active nature of copper which enables a reduction from Cu^II to Cu^I, occurring upon ESI‐MS, whereas Co^II, Ni^II and Zn^II cannot undergo similar redox reactions. Copyright © 2009 John Wiley & Sons, Ltd.     

Metal chelates of thiazole-2-ylthiourea

Summary The formation constants of 1-phenyl-3-thiazole-2-ylthiourea complexes with some bivalent metal ions (Cu^II, Ni^II, Zn^II and Mn^II) have been determined in 75% EtOH–H₂O. Complexes of Cu^II, Ni^II, Zn^II, Hg^II and Pd^II have been isolated and characterized by conductance, i.r., electronic spectra and magnetic measurements. The ligand forms ML complexes with Cu^II and Hg^II and ML₂ with Ni^II, Zn^II and Pd^II, where L is the uninegatively charged bidentate ligand and binds through the ring nitrogen and thiocarbonyl sulphur atoms.     

A new oxamato-bridged heterotrinuclear NiIICuIINiII complex: synthesis,structure and properties

A new oxamato-bridged Ni^IICu^IINi^II species, [Ni(iprtacn)]₂[Cu(pba)(H₂O)_0.5](BPh₄)₂ (1), (iprtacn?=?1,4,7-triisopropyl-1,4,7-triazacyclononane; pba?=?1,3-propylenebis(oxamato)) has been synthesized and structurally as well as magnetically characterized. Complex 1 has a discrete trinuclear Ni^IICu^IINi^II structure: Two nickel(II) ions are bridged by [Cu(pba)]^2? with the macrocyclic ligand iprtacn a terminal ligand of nickel(II). Fitting the magnetic data of 1 led to g _Cu?=?2.16, g _Ni?=?2.18, J?=??112.5?cm^?1, D?=?±7.78?cm^?1. The irregular spin state structure and interaction of complex 1with DNA are described here.     

Postsynthetic Improvement of the Physical Properties in a Metal–Organic Framework through a Single Crystal to Single Crystal Transmetallation

A single crystal to single crystal transmetallation process takes place in the three‐dimensional (3D) metal–organic framework (MOF) of formula Mg^II₂{Mg^II₄[Cu^II₂(Me₃mpba)₂]₃}?45 H₂O ( 1 ; Me₃mpba^4?=N,N′‐2,4,6‐trimethyl‐1,3‐phenylenebis(oxamate)). After complete replacement of the Mg^II ions within the coordination network and those hosted in the channels by either Co^II or Ni^II ions, 1 is transmetallated to yield two novel MOFs of formulae Co₂^II{Co^II₄[Cu^II₂(Me₃mpba)₂]₃}?56 H₂O ( 2 ) and Ni₂^II{Ni^II₄[Cu^II₂(Me₃mpba)₂]₃}? 54 H₂O ( 3 ). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties.     

A click fluorophore sensor that can distinguish Cu(II) and Hg(II) via selective anion-induced demetallation

A cyclam‐based fluorescent sensor featuring a novel triazole pendant arm has been synthesised using click chemistry. The sensor is highly responsive to both Cu^II and Hg^II in neutral aqueous solution and displays excellent selectivity in the presence of various competing metal ions in 50‐fold excess. The addition of specific anions such as I^? and S₂O₃^2? causes a complete revival of fluorescence only in the case of Hg^II, providing a simple and effective method for distinguishing solutions containing Cu^II, Hg^II or a mixture of both ions, even in doped seawater samples. X‐ray crystal structures of both the Hg^II sensor complex and a model Cu^II complex show that pendant triazole coordination occurs through the central nitrogen atom (N2), providing to the best of our knowledge the first reported examples of this unusual coordination mode in macrocycles. Fluorescence, mass spectrometry and ¹H NMR experiments reveal that the mechanism of anion‐induced fluorescence revival involves either displacement of pendant coordination or complete removal of the Hg^II from the macrocycle, depending on the anion.     

The assembly,synthesis and properties of a trinuclear cyano-bridged CuII–MoIV–CuII complex

A new trinuclear cyano-bridged Cu^II–Mo^IV–Cu^II compound has been prepared, characterized spectroscopically (UV–Vis and IR) and its structure determined by X-ray crystallography. The title complex 1 exhibits an antiferromagnetic exchange interaction between copper(II) ions mediated by [Mo(CN)₈]^4? diamagnetic units.     

Bis{[μ‐N,N′‐bis­(salicyl­idene)‐1,4‐butane­di­amine‐N,N′,O,O′‐copper(II)]‐μ‐chloro‐chloromercury(II)}

A new tetranuclear Cu^II–Hg^II–Hg^II–Cu^II complex, [Cu₂Hg₂Cl₄(C₁₈H₁₈N₂O₂)₂], has been prepared by means of a copper complex found in the literature. The molecular structure of this complex was determined by X‐ray diffraction and the Cu–Hg–Hg–Cu chain was seen to be non‐linear. The change in magnetic susceptibility with temperature was recorded for this complex and observed to abide by the Curie–Weiss law. The coordination around the Hg^II ions is square pyramidal. The Cu?Hg bridging distance is 3.5269 (7) Å.     

2D Compound Constructed by Cu3 Units with Mixed Azido and Tetrazole Double Bridges: Synthesis,Structure, and Theoretical Study on Magnetic Properties

The two‐dimensional (2D) layer Cu^II compound [Cu₃(L)₂(N₃)₄] ( 1 ) [L = 2‐amino‐3‐(5‐tetrazole)‐methyate‐N‐pyridine] was synthesized by in‐situ hydrothermal reaction of CuCl₂ · 2H₂O, NaN₃, and 3‐(5‐tetrazole)‐methyate‐N‐pyridine. The central Cu1 and Cu2 atoms are located in five‐coordinate and six‐coordinate arrangements, respectively. Three Cu^II ions are linked by mixed double EO (end‐on)‐azido‐tetrazole bridges to give trinuclear Cu^II clusters, which are further extended by EE (end‐to‐end) azido bridges to form 2D metal‐organic layers. The magnetic exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –849 cm^–1) revealed that the double EO‐azido‐tetrazole bridges transmit antiferromagnetic coupling between Cu^II ions.     

Mosaic CuI−CuII−InIII 2D Perovskites: Pressure-Dependence of the Intervalence Charge Transfer and a Mechanochemical Alloying Method

The perovskite (BA)₄[Cu^II(Cu^IIn^III)_0.5]Cl₈ ( 1_BA ; BA⁺=butylammonium) allows us to study the high-pressure structural, optical, and transport properties of a mixed-valence 2D perovskite. Compressing 1_BA reduces the onset energy of Cu^I/II intervalence charge transfer from 1.2 eV at ambient pressure to 0.2 eV at 21 GPa. The electronic conductivity of 1_BA increases by 4 orders of magnitude upon compression to 20 GPa, when the activation energy for conduction decreases to 0.16 eV. In contrast, Cu^II perovskites achieve similar conductivity at ≈50 GPa. The solution-state synthesis of these perovskites is complicated, with more undesirable side products likely from the precursor mixtures containing three different metal ions. To circumvent this problem, we demonstrate an efficient mechanochemical synthesis to expand this family of halide perovskites with complex composition by simply pulverizing together powders of 2D Cu^II single perovskites and Cu^IIn^III double perovskites.     

Copper and copper-palladium catalysts of aliphatic thiols oxidation in biological objects: Quantum-chemical DFT simulation

DFT calculations (M06, PBE0/Def2-TZVP) of coordination compounds used in reactions of selective oxidation of thiols to disulfides were performed. Primary active centers of the catalysts are polynuclear scaffolds {L₂M(μ-OH)₂ML₂}²⁺ and {L₂M(μ-OH)₂M′(μ-OH)₂ML₂}²⁺ (M = Cu^I, Cu^II, Pd^II; M' = Cu^II; L = NH₃). Cu^II ions in combination with PdII ions are capable of formation of polynuclear active center {PdII(μ-OH)₂Cu^II(μ-OH)₂Pd^II}²⁺ bringing together a large number of mutually oriented RS^– groups and thus affecting the rate of formation of disulfide R₂S₂.