The metal-complexing properties of N-benzoyl-N-phenylhydroxylamine derivatives containing N-phenyl ring substituents

The syntheses and chelating properties of a number of N-benzoyl-N-phenylhydroxyl-amine derivatives substituted in the N-phenyl ring have been investigated. The acid dissociation constants, selective precipitation, solvent extraction and spectrophotometric properties of a range of metal chelates are compared with those of the corresponding 3,5-dinitrobenzoylphenylhydroxylamines. The N-phenyl ring substituents have only small effects on reagent acidity. If the substituents are in the ortho position, considerable selectivity is found because of steric hindrance. The use of an o-chloro derivative as a selective precipitant for iron(III) in the presence of cobalt, nickel, copper and aluminium, is described.     

Amphiphilic polymer supported N-heterocyclic carbene palladium complex for Suzuki cross-coupling reaction in water

We synthesized amphiphilic polymer-supported N-heterocyclic carbene (NHC) precursor resins by loading polyethylene glycol (PEG) containing imidazolium groups on Merrifield resin. These PS-PEG-NHC precursor resins were compatible with water and readily formed a stable complex with palladium. These PS-PEG-NHC-Pd catalysts showed excellent catalytic activity for Suzuki cross-coupling reactions of various aryl iodides and bromides with phenylboronic acid in water than the previously described polystyrene based catalysts. In addition, the PS-PEG-NHC-Pd catalysts continued to provide excellent catalytic activity in Suzuki cross-coupling reactions after five consecutive recycles.     

Synthesis and structure of metal complexes containing zwitterionic N-hydroxyimidazole ligands

Cu(II) and Zn(II) complexes of N-hydroxyimidazoles were synthesised by reacting simple metal perchlorate salts with the imidazole ligand in alcohol and formulated with a metal:ligand ratio of 1:2. The X-ray crystal structures of five complexes (four Cu(II) and one Zn(II)) were obtained and each showed the two trans, N-hydroxyimidazole ligands forming six-membered, chelate rings with the metal. Both of the NO chelating, neutral N-hydroxyimidazole ligands are in the zwitterion form, with the uncoordinated imidazole imine N atom being protonated and the oxime O atom deprotonated. In the solid state the complexes form hydrogen-bonded supramolecular structures.     

Separation of beryllium and aluminium from other elements using an ion-exchange resin with N-benzoylphenylhydroxylamine as a functional group

A chelating polystyrene-divinylbenzene-based resin containing N-benzoylphenylhydroxylamine as the chelating group was synthesized and characterized through its water regain capacity (0.56 g g^?1) and stability towards acids, alkalis, heat and γ-radiation. The effective pH for use of the resin was 1.0–7.0 for beryllium, 2.5 for aluminium and 6.5 for coppjt]Analyst     

Extraction-photometric determination of vanadium(V) with N-hydroxy-N-m-tolyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine hydrochloride in the presence of acetic,monochloroacetic, and phenylacetic acids

N-Hydroxy-N-m-tolyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine hydrochloride (HTMCPTH), a monobasic and bidentate chelating agent which reacts with vanadium(V) in carboxylic acid media to develop a blue-violet complex, has been employed as a highly selective reagent for extraction and direct photometric determination of the metal. Solvent extraction experiments indicate that from aqueous acetic acid (1.0–10.0 M), monochloroacetic acid (0.1–10.0 M), and phenylacetic acid (at pH 0.5–6.0) vanadium(V) is quantitatively extracted into chloroform. Almost all common ions including Fe³⁺, Cu²⁺, Ni²⁺, Co²⁺, Mn²⁺, Cr³⁺, Ti⁴⁺, Zr⁴⁺, and Mo⁶⁺ do not interfere with the proposed method. The procedure has been utilized for accurate determination of vanadium in standard steels.     

Synthesis and application of modified poly (styrene‐alt‐maleic anhydride) networks as a nano chelating resin for uptake of heavy metal ions

A chelating resin based on modified poly (styrene‐alt‐maleic anhydride) with 3‐aminobenzoic acid was synthesized. This modified resin was further reacted by 1,2‐diaminoethane or 1,3‐diaminopropane in the presence of ultrasonic irradiation to prepare tridimensional chelating resin for the removal of heavy metal ions from aqueous solutions. The adsorption behavior of Fe(II), Cu(II), Zn(II) and Pb(II) ions was investigated by synthesized chelating resins in various pH. Among the synthesized resins, CSMA‐AB1 and CSMA‐AB2 demonstrated a high affinity for the selected metal ions compared to SMA‐AB, and the order of removal percentage changes as follow: Fe(II) > Cu(II) > Zn(II) > Pb(II). The adsorption of all metal ions in acidic medium was moderate, and it was favored at the pH value of 6 and 7. Also, the prepared resins were examined for removal of metal ions from industrial wastewater and were shown to have a very efficient adsorption in the case of Cu(II), Fe(II) and Pb(II); however, the adsorption of Zn(II) was lower than others. The resin was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction analysis and thermogravimetric analysis/derivative thermogravimetry. Copyright © 2012 John Wiley & Sons, Ltd.     

Application of thermodynamics in a specific force field to the adsorption of Al ions on the chelating resins Ostsorb Oxin, Ostsorb Salicyl, Spheron Oxin, and Spheron Salicyl: Mathematical analysis of sorption isotherms using nonlinear mean square software

The sorption mechanism of Al³⁺ on chelating resins by means of mathematical analysis of sorption isotherms using nonlinear mean square software was studied. This method should yield more detailed information than classical thermodynamics and should be more flexible than the statistical-mechanical method, so that it would make it possible to obtain fairly easily relations directly applicable in practice. This model defined the specific potential Φ_Al^R for the ion in a resin (which depends on properties of resin and ion). On the basis of this model, N and PO isotherms were derived. To study the sorption mechanism, the Freundlich, Langmuir, N and PO equations (models) of isotherms were used. It was estimated that the functional groups (8-hydroxyquinoline and salicylate) in the studied chelating resins influence Φ_Al^R and thus their mechanism and sorption capacity.     

Catalytic photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine and carbon dioxide

Photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine (TMB) in MeCN under bubbling of CO₂ proceeded with high catalytic efficiency, giving 3,3-diphenylacrylic acid (DPA) and 3-hydroxy-3,3-diphenylpropionic acid (20). The turnover number (TON=(DPA+20)/TMB) reached 17. Similarly, 1-phenyl-1-cyclohexene yielded cis-2-acetamido-2-phenylcyclohexanecarboxylic acid with TON 5.9. As compared with related N,N-dimethylaniline derivatives, TMB is more resistant to photodecomposition, has the much larger absorbance in the S₀→S₁ transition, and has the lower quenching efficiency by CO₂. Probably these factors are partly responsible for the high TON observed for TMB.     

Enhanced metal extractive behavior using dual mechanism bifunctional polymer: an effective metal chelatogen

A new class of chelating polymers using Amberlite XAD-16 (AXAD-16) modified with (N-(3,4-dihydroxy)benzyl)-4-amino,3-hydroxynapthalene-1-sulphonic acid has been developed based on dual mechanism bifunctional polymers, for the extraction of transition and post-transition metal ions. The optimum pH conditions for the quantitative sorption of metal ions were studied. The developed method showed superior extraction qualities with high metal loading capacities of 71, 85, 182, 130 and 46 mg g⁻¹ for Ni(II), Cd(II), Pb(II), Cu(II) and Co(II), respectively. The rate of metal ion uptake i.e. kinetics studies performed under optimum levels showed a time duration of <5 min except for Co(II) which required 20 min, for complete metal ion saturation. Desorption of metal ions were effective with 15 ml of 2 M HCl/HNO₃ prior to detection using flame atomic absorption spectrophotometer. The chelating polymer was highly ion-selective in nature even in the presence of large concentrations of alkali and alkaline earth metal ions, with a high preconcentrating ability for the metal ions of interest. The developed chelating matrix was tested on its utility with synthetic and real samples like river/sea/tap/well water samples and also with multivitamin/mineral tablets, showed R.S.D. values of <2.5% reflecting on the accuracy and reproducibility of data using the newly developed resin matrix.     

Sorption investigation on the removal of metal ions from aqueous solutions using chelating terpolymer resin

A novel chelating terpolymer resin has been synthesized from anthranilic acid, phenylhydrazine, and formaldehyde by condensation in glacial acetic acid. The structure of the chelating resin was clearly elucidated by use of a variety of spectral techniques, for example FTIR, and ¹H and ¹³C NMR spectroscopy. The average molecular weight of the terpolymer resin was determined by gel-permeation chromatography. The empirical formula and empirical weight of the resin were determined by elemental analysis. The physicochemical properties of the terpolymer resin were determined. Scanning electron microscopy was used to establish the surface features of the chelating resin. The ion-exchange behaviour of the resin for specific metal ions, viz. Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Pb²⁺, was evaluated by a batch equilibrium method. The study was extended to three variations: evaluation of metal ion uptake in the presence of different electrolytes at different concentrations; evaluation of metal ion uptake at different pH; and evaluation of metal ion uptake at different times. Further, the reusability of the resin was also determined to assess the efficiency of the resin after a few cycles of sorption. From the results it was observed that the resin acts as an effective chelating ion-exchanger.     

Preconcentration and separation of copper (II) with solvent extraction using N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2 diaminopropane

Preconcentration and separation with solvent extraction of Cu(II) from aqueous solution using N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2 diaminopropane (H₂L) as the new extractant has been studied. Separation of Cu(II) from other metal ions such as Cd(II), Ni(II), Zn(II), Pb(II), Cr(III), Co(II) and Mn(II) at aqueous solutions of various pH values and complexing agent H₂L, has been described. The possible extraction mechanism and the compositions of the extracted species have been determined. The separation factors for these metals using this reagent are reported while efficient methods for the separation of Cu(II) from other metal ions are proposed. From the loaded organic phase, Cu(II) stripping was carried out in one stage with different mineral acid solutions. The stripping efficiency was found to be quantitative in case of HNO₃ and HCl. From quantitative evaluation of the extraction equilibrium data, it has been deduced that the complex extracted is the simple 1:1 chelate, CuL. The extraction constant has a value of logK_ex=−4.05±0.04.     

Peptide thioester preparation based on an N-S acyl shift reaction mediated by a thiol ligation auxiliary

Formation of peptide thioesters, based on an N to S acyl shift mediated by an auxiliary, N-4,5-dimethoxy-2-mercaptobenzyl (Dmmb) group, under acidic conditions, is described. The protected peptide was assembled on a hydroxymethylphenylacetamidomethyl resin via an N-Dmmb-amino acid residue according to standard Fmoc solid-phase peptide synthesis following treatment with trifluoroacetic acid. The peptide α-thioester was released from the resin by reaction with 2-mercaptoethanesulfonic acid in the presence of N,N-diisopropylethylamine.     

Selective functionalization at the small rim of calix[6]arene. Synthesis of novel non-symmetrical N3, N4 and N3ArO biomimetic ligands

Eight novel calix[6]arene-based biomimetic ligands for transition metal ions have been synthesized. They display a non-symmetrical N₃, N₄ or N₃ArO binding core that mimics enzyme active sites presenting histidine and tyrosine residues. The key step for their synthesis is the mono-alkylation at the small rim of the C_3v symmetrical trimethyl ether derivative of tBu-calix[6]arene with N-Boc-2-chloroethylamine to yield a novel calix[6]arene synthon. Its combined O-alkylation with a chloromethyl aromatic amine and N-deprotection or alkylation or reductive alkylation with a salicylaldehyde derivative yielded the calix[6]arene-based ligands with mixed N/O donors.     

Coordination steric effect of N,N-dimethylformamide, N,N-dimethylacetamide and N-methyl-2-pyrrolidone on the assembly of coordination polymers

Three coordination polymers 1, 2 and 3 have been synthesized in DMF (N,N-dimethylformamide), DMA (N,N-dimethylacetamide) and NMP (N-methyl-2-pyrrolidone), respectively. In 1, DMF solvent molecule coordinates to zinc ion as an ancillary ligand, and 1D chain structure is obtained. 2 and 3 are isostructural, in which solvent molecules, DMA and NMP, do not coordinate to zinc ions, and 1D double stranded chain structures are formed. The coordination steric hindrance of the solvents is suggested as the decisive factor of the assemblies. Crystallography and thermoanalysis reveal that 2 and 3 are more stable and also include more guest solvent molecules than 1.     

Synthesis and aromatic nucleophilic N-N, N-S and N-O exchange reactions of N,N-dimethyl-2-trifluoroacetyl-1-naphthylamine

We succeeded in the synthesis of N,N-dimethyl-2-trifluoroacetyl-1-naphthylamine (10) by the regioselective deacylation of N,N-dimethyl-2,4-bis(trifluoroacetyl)-1-naphthylamine with trifluoroacetic acid and water. The aromatic nucleophilic substitutions of 10 with various amines, thiols and alcohols proceeded cleanly to give the corresponding N-N, N-S and N-O exchanged products in moderate to excellent yields.     

SYNTHESES AND ADSORPTION PROPERTIES OF PHENOL-FORMALDEHYDE-TYPE CHELATING RESINS BEARING THE FUNCTIONAL GROUP OF TARTARIC ACID

Several kinds of novel chelating resins bearing the functional group of tartaric acid (TTA-FQ-12, TTA-FQ-23, and TTA-FQ-34) were synthesized by reacting epoxy maleic anhydride, which was prepared through the oxidization reaction of maleic anhydride by hydrogen peroxide, with phenol-formaldehyde resin containing polyamine (FQ resins series). The effects of such factors as reaction time, reaction temperature and pH value on the loading capacity of TTA in resins were investigated. The results showed that the optimum reaction conditions are as follows: time 9-12h; temperature 90-105℃;pH value 6-10. The loading capacities of TTA can reach 0.15, 0.14, and 0.11 mmol/g^-1 when the functional group of FQ resin was -OCH2CH2NHC2H4NH2, -O(CH2CH2NH)2C2H4NH2 and -O(CH2CH2NH)3C2H4NH2), respectively. The structures of resins were characterized by FTIR spectra. The primary study on the adsorption properties of the resins for metal ions showed that there are two kinds of adsorption mechanisms i.e. ion exchange and chelate in the adsorption process. TTA-FQ resins have much higher adsorption selectivity for Pb^2 and Zn^2 than for Cu^2 and Ni^2 . These resins can probably be used for separating Pb^2 or Zn^2 in the mixture of metal ions or for treating wastewater containing heavy metal ions.     

Physico‐Chemical Studies on Cu(II) Complexes of Acrylate Chelating Polymers

Abstract

Metal chelating polymers containing amide and carboxylic groups were prepared by gamma‐radiation polymerization of acrylic acid (AA) monomers in the presence of polyacrylamide (PAM). The resins obtained were loaded by copper ions and characterized by FT‐IR spectroscopy, electron spin resonance (ESR), thermogravimetric analysis (TGA), and differential scanning calorimetery (DSC). The IR spectra indicated a lower frequencies shift in the carbonyl bands due to copper ion chelation with carbonyl groups in the polymer resins. Also, the IR spectra reveal a splitting in the band at 3600–3200?cm^?1 that due to the coordination of the NH and OH groups with copper ions. The ESR spectrum was anisotropic with hyperfine structure having the following values 2.3808 and 2.07218 for g _∥ and g _⊥, respectively. These spectra for copper ions have square planar coordination with two nitrogen and two oxygen atoms. TGA and DSC studies show that radiation crosslinking and complexation with copper ion increase the thermal stability of PAM–AA resins. Meanwhile, resin complexes with copper ion showed a higher thermal stability than pure resin. The increase in thermal stability may be correlated with the metal ions coordination with NH and OH groups; this coordination prevents the splitting of ammonia and water molecules. Also, the metal ions providing a coordination crosslink between polymer chains could increase thermal stability.     

Solvent extraction and photometric determination of a microgram of cerium with N-p-tolyl-p-chlorobenzohydroxamic acid

A spectrophotometric method for determination of a microgram quantity of cerium with N-p-tolyl-p-chlorobenzohydroxamic acid is described. The orange-red-colored complex is extracted from chloroform at pH 9 which absorbs between 460 and 465 nm. Beer's law is obeyed at this wavelength. A clean-cut separation from many commonly occurring metal ions is easily accomplished. The system obeys Beer's law within the range of 0.5–28 ppm of cerium(IV). The molar absorptivity of cerium-N-p-tolyl-p-chlorobenzohydroxamic acid complex is 4.5 × 10³ liters mol^?1 cm^?1.     

Development of column-pretreatment chelating resins for matrix elimination/multi-element determination by inductively coupled plasma-mass spectrometry

Chelating resins, two kinds of iminodiacetate derivatives (IDA) of cross-linked chitosan (CCS) were synthesized and investigated for adsorption capacity, matrix elimination and collection/concentration of analytes by a column pretreatment in a multi-element ICP-MS determination method. The adsorption behavior of 54 elements at the 10 ng ml(-1) level on chitosan derivatives in a packed mini-column was systematically examined. Almost 30 kinds of metal ions were recovered quantitatively at pH 5 with CCS-HP/IDA (cross-linked chitosan possessing N-2-hydroxypropyl iminodiacetic acid groups) column. Compared with available chitosan-iminodiacetate resin, CHITOPEARL CI-03, the recovery of the metal ions such as Cu, Pb and La is satisfactory with CCS-IDA (cross-linked chitosan possessing N,N-iminodiacetic acid groups) and CCS-HP/IDA using 2 M nitric acid as an eluent, which may be attributed to the difference of cross-linking and macroporous structure. Compared with Chelex-100, the adsorption efficiency is in the order: Chelex-100 > CCS-IDA > CCS-HP/IDA, especially in the chelating ability for alkaline earth metals. The resin with a longer spacer (CCS-HP/IDA) showed higher adsorption selectivity between heavy metal ions and alkaline earth metals at pH < 7. The separation efficiency of the major matrix cations in seawater (Na. K, Mg, Ca) has also been investigated, and matrix interference was negligible even in a seawater sample at pH 5 with CCS-HP/IDA. The recoveries of Mn at pH 5 with CCS-HP/IDA or Chelex-100 were almost 100%. However, those of Mg with each resin were 4 or 98%, respectively. The adsorption capacities of synthesized CCS-HP/IDA for Cu(II), Pb(II) and La(III) were 0.90, 0.65 and 0.34 mmol g(-1), respectively. Therefore, the chelating chitosan resins developed are applicable to the pretreatment of trace amounts of elements in various kinds of water samples.     

Theoretical study on the interaction of sulfur‐ and aminopyridine‐containing chelating resins with Hg(II) and Pb(II)

The geometries and energetics of complexes of Hg(II) and Pb(II) with sulfur‐ and aminopyridine‐containing chelating resin including crosslinked polystyrene immobilizing 2‐aminopyridine via sulfur‐containing (PVBS‐AP), sulfoxide‐containing (PVBSO‐AP), and sulfone‐containing (PVBSO₂‐AP) spacer arms have been investigated theoretically, and thus interactions of the metal ions with chelating resins were evaluated. The results indicate that PVBS‐AP behaves as a tridentate ligand to coordinate with the metal ions by S and two N atoms to form chelating compounds with S atom playing a dominant role in the coordination, whereas PVBSO‐AP and PVBSO₂‐AP interact with metal cations, respectively, in a tricoordinate manner by O and two N atoms forming chelating complexes. Furthermore, it is revealed that O and N2 atoms of PVBSO‐AP are the main contributor of coordination to Hg(II), whereas N2 atom of PVBSO₂‐AP is mainly responsible for the coordination to Hg(II). For PVBSO‐AP‐Pb²⁺ and PVBSO₂‐AP‐Pb²⁺ complex, the coordination is dominated by the synergetic effect of N1, N2, and O atoms. Natural bond orbital and second‐order perturbation analyses suggest that the charge transfer from the chelating resins to metal ions is mainly dominated by the interactions of lone pair of electrons of the donor atoms with the unoccupied orbitals of metal ions. Hg(II) complexes exhibit larger binding energies than the corresponding Pb(II) complexes, implying the chelating resins exhibit higher affinity toward Hg(II), which is consistent with the experimental results. Combined the theoretical and experimental results, further understanding of the structural information of the complexes and the coordination mechanism was achieved. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011