Chelate Polymers. V. Novel Alternating Copolymers Based on Transition Metal–Azomethine Complexes and Siloxanes

Abstract

The Schiff base of 2,4‐dihydroxybenzaldehyde with ethylenediamine has been prepared and complexed with two different divalent metals: Cu(II) and Ni(II). The resulting bisphenolic chelates were inserted in new alternating polymeric structures by their polycondensation with 1,3‐bis‐(chloromethyl)‐1,1,3,3‐tetramethyldisiloxane or α, ω‐bis(chloromethyl)oligodimethylsiloxanes having different numbers of siloxane units in the chains. In order for their activation, the chelates were converted in salt forms by previously treating them with a NaOH 0.1 N solution or in situ in the presence of anhydrous K₂CO₃. DMF was used as a solvent. The structures of the ligand, complexes, and polymers obtained on their basis were confirmed by IR, UV, and ¹H NMR. Characterization was undertaken by thermogravimetric analysis (TGA), solubility tests, and viscosity measurements.     

TRENDS IN THE OPTICAL ROTATORY DISPERSION SPECTRA OF R-(−)-1,2-PROPYLENEDIAMINETETRAACETATO COMPLEXES OF GROUPS IIA,IIB,IIIA,IIIB,IVB AND SOME HEAVY METALS

Abstract

A general periodic trend was observed in the optical rotatory dispersion spectra of the R-(?)-1,2-propylenediamine-tetraacetato (R(?)PDTA) complexes of Group IIA metals: magnesium(II), calcium(II), strontium(II), and barium(II); Group IIIB metals: scandium(III), yttrium(III), and lanthanum(III); Group IVB metals: titanium(IV), zirconium(IV), and thorium(IV); Group IIB metals: zinc(II), cadmium(II), and mercury(II); Group IIIA metals: aluminum(III), indium(III), and thallium(III); and the heavy metals: mercury(II), thallium(III), lead(II), and bismuth(III). The periodic trend was related to the ionic potential of the metals within each group, in that as the ionic potential increases within a group, the molecular rotations decrease from a positive to a negative value at any given wavelength outside of a region of anomalous optical rotatory dispersion. Comparing the heavy metal, mercury(II), lead(II), thallium(III), and bismuth(III), complexes of R(?)PDTA, outside of the region of anomalous rotatory dispersion, the metal with the same charge but smaller ionic potential has the greater positive molecular rotation at any given wavelength.     

Simultaneous Determination of Heavy Metals in Bovine Liver and Oyster Tissue by Solvent Extraction-Reversed Phase High Performance Liquid Chromatography

Abstract

High performance liquid chromatographie method for the simultaneous determination of ppm levels of cadmium, nickel, lead, zinc, cobalt, copper and bismuth in biological samples has been developed. Each 250 mg of Bovine Liver(NBS 1577) or Oyster Tissue(NBS 1566) was ashed in a muffle furnace over night at 500 to 55O°C. Then the ash was treated with 1.5 ml of 2 N hydrochloric acid; and the solution was put into a separatory funnel. The dissolved heavy metals were extracted into chloroform as hexamethylenedithiocarbamato chelates. The metal chelates were separated on a reversed phase column(5 μm, ODS, 4.6 × 15O mm), and determined by measuring the peak height of each metal chelate. Cd, Ni, Pb, Zn and Cu were determined accurately over the concentration range of 0.5–850 ppm with standard deviation ca. 7%.     

A Simple Analytical Method for Monitoring the Total Concentration of Heavy Metal Ions in Environmental Waters

Abstract

A non-sophisticated analytical procedure has been developed for monitoring the sum of heavy metal elements which form stronger EDTA complexes than manganese(II). It is based on complexation of the heavy metals with EDTA and a catalytic indication of its stoichiometry. The equivalence point is determined visually using the substitution reaction between Mn(II)-EDTA and heavy metal ions, followed by the Mn(II)-catalyzed oxidation of Acid Blue 45 dye with hydrogen peroxide. The method has a reasonable accuracy, uses simple test equipment and stable reagents, there are few interferences and it can be carried out by non-technical personnel. Neither preconcentration nor dilution of the sample is required and it is applicable to aqueous samples containing heavy metals down to ppm levels. Some applications to river and groundwaters are shown.     

Pre-column chelation liquid chromatographic separation and determination of trace V,Cu, Co,Pd, Fe and Ni

Conditions for the separation by reversed-phase liquid chromatography (LC) of V(V), Cu(II), Co(III), Pd(II), Fe(III) and Ni(II) chelates with 2-(5-bromopyridylazo)-5-diethylaminophenol (5-Br-PADAP) were studied. Six species of metal chelates were separated successfully with methanol-acetonitrile-water (72:12:16, v/v/v) containing 0.13 M NaCl and 0.29 mM cetyltrimethylammonium bromide (pH 5.0) as the mobile phase on a Nucleosil C₁₈ (5 μm) column (250 × 4 mm i.d.).The conditions of the determination of these metal chelates are discussed. A simple and rapid method for the determination of trace amounts of V(V), Cu(II), Co(III), Pd(II) and Ni(II) simultaneously by reversed-phase LC has been developed. The detection limits are 5 × 10^?12, 1 × 10^?10, 3 × 10^?11, 5.3 × 10^?9 and 2 × 10^?10 g, respectively. The method is applied to the determination of these metals in natural waters and mineral samples.     

Incorporation of transition metals into Mg-Al layered double hydroxides: Coprecipitation of cations vs. their pre-complexation with an anionic chelator

A comparative study on two different methods for preparing Mg-Al layered double hydroxides (LDH) containing various divalent transition metals M (M=Co, Ni, Cu) has been carried out. The first (conventional) method involved coprecipitation of divalent metals M(II) with Mg(II) and Al(III) cations using carbonate under basic conditions. The second approach was based on the ability of transition metals to form stable anionic chelates with edta⁴⁻ (edta⁴⁻=ethylenediaminetetraacetate) that were synthesized and further introduced into LDH by coprecipitation with Mg and Al. The synthesized LDHs were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) methods, thermogravimetry with mass-selective detection of decomposition products (TG-MSD), Fourier transform infrared (FTIR) and Raman spectroscopy techniques. The results obtained were discussed in terms of efficiency of transition metal incorporation into the LDH structure, thermal stability of materials and the ability of metal chelates to intercalate the interlayer space of Mg-Al LDH. Vibrational spectroscopy studies confirmed that the integrity of the metal chelates was preserved upon incorporation into the LDH.     

SERS approach for Zn(II) detection in contaminated soil

Soil contamination by metals is a common problem encountered in many industrialized countries. In this work we present a new approach for heavy metals detection by using surface-enhanced Raman scattering (SERS) spectroscopy. Zn(II) can be clearly determined by SERS in contaminated soil by using 4-(2-pyridylazo) resorcinol (PAR) as chelating molecule for the metal ion. The SERS spectra of PAR, of its metal chelates and of the soil extract-PAR mixture were recorded using a hydroxylamine reduced silver colloid. An excellent match of the PAR-contaminated soil extracts SERS spectrum to the Zn(PAR)₂ SERS spectrum can be observed, demonstrating the presence of Zn(II) in the soil probes. Density functional theory (DFT) based calculations were also performed for a reliable assignment of SERS spectra.     

The High Pressure Liquid Chromatogrpaphy of Metal Chelates of Diethyldithiocarbmic Acid and Dithizone

Abstract

The HPLC behavior of Ni(II), Co(III), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) chelates of diethyldithiocarbamic acid, H(DDTC), and dithizone, H(D_z), was studied on silica gel columns with toluene as the mobile phase. Calibration plots gave linear results for plots of peak area vs. amount of metal injected over the low nanogram to milligramrange. Calibration plots for the above cations were determined on the basis of 3 to 5 replicate determinations for 8 to 10 different concentration levels over the above range with a relative standard deviation less than 5.0% for all metals studied. A variable wavelength photometric detector was used and the detection limits at 270 nm were in the range of 5 to 200 ng depending on the metal species. The best separations were obtained on a1/4″ × 35 cm stainless-steel packed with 10 micron μ-Porasil.     

Liquid chromatographic determination of chelates of cobalt (II), copper (II) and iron (II) with 2-thiophonaldehyde-4-phenyl-3-thiosemicarbazone

Summary A new chelating reagent 2-thiophenaldehyde-4-phenyl-3-thiosemicarbazone (TAPT) has been examined for high performance liquid chromatographic (HPLC) separations of cobalt (II), copper(II) and iron (II) or cobalt (II), nickel (II), iron (II), copper (II) and mercury (II) as metal chelates on a C₁₈, 5μm column (250×4 mm i.d.) The chelates were eluted isocratically with methanol: acetonitrile: water containing sodium acetate and tetrabutylammonium bromide (TBA), and detected at 254 nm. A solvent extraction procedure was developed for simultaneous determination of the metals with detection limits within 0.02–2.5 μ g.mL⁻¹. The method was applied to the determination of copper, cobalt and iron in natural waters.     

One-pot synthesis of a novel magnetic activated carbon/clay composite for removal of heavy metals from aqueous solution

Abstract

In the present work, a novel composite consisting of magnetite, activated carbon from spent coffee grounds and natural clay (MACCC) was prepared by a one-pot synthesis method via a simultaneous activation and magnetization processes. Various techniques (XRD, FTIR, SEM, TEM, EDX, BET) were utilized to characterize the synthesized composite before utilizing it as an adsorbent for removal of Cu(II), Ni(II) and Pb(II) ions from aqueous solutions. Conditions for removal of heavy metals were thoroughly optimized as 25?°C, pH of 5.5, adsorbent dosage of 2?g L^?1, and a contact time of 60?min. Three models of pseudo first-, second-order and intraparticle diffusion as well as three models of Langmuir, Freundlich, and Temkin were used to analyze kinetics and isotherms of the adsorption process. Thermodynamics was discussed completely. Regeneration and recyclability of the adsorbent were also evaluated. Based on the analysis of experimental results, a possible adsorption mechanism of heavy metals onto the synthesized composite was proposed. The maximum capacities caculated from Langmuir model followed the order of Pb(II) > Cu(II) > Ni(II) as 143.56, 96.16 and 84.86?mg·g^?1, respectively. The overall results indicated that MACCC is a potential adsorbent for removal of toxic Pb(II), Cu(II) and Ni(II) ions from wastewater due to simple preparation, high removal efficiency and good recyclability.     

Metal chelates of ampicillin versus amoxicillin: synthesis,structural investigation,and biological studies

Solid chelates derived from some alkaline earth and transition metal complexes with ampicillin (Hamp, a) and amoxicillin (Hamox, b) were synthesized and characterized using elemental analysis, molar conductivity, IR, magnetic susceptibility, and thermogravimetric studies. Both drugs behave as tetradentate ligands coordinating to metal through amino, imino, and carboxylate as well as through β-lactamic carbonyl. All chelates have octahedral geometry except Cu(II) complexes which have square planar structure and uranium has pentagonal bipyramidal coordination. ¹H- and ¹³C-NMR of the Zn(II) and UO₂(VI) chelates are compared with the free ligands. The antimicrobial activity of the prepared chelates was determined.     

Analytical Separations of Schiff Base Chelates by Reverse Phase Hplc on a 10 Micron C-18 Bonded Silica Subtrate

Abstract

Reverse phase partition chromatography on a 10 micron silica-bonded octadecyl hydrocarbon substrate is applied to the separation of neutral tetradentate chelates of copper (II), nickel (II) and palladium (II) with a range of non-fluorinated and fluorinated beta-ketoamine and salicylaldimine ligands. Variation of retention and resolution with respect to changes in ligand structure and metal chelated is investigated using acetonitrile, methanol and water solvent systems. Detection limits (254 nm) and linearity ranges of response are indicated.     

Thin-Layer Chromatography of Metal Ions Complexed with Anils (V). Detection,Separation and Determination

Abstract

p-Diethylaminoanil of phenylglyoxal a bidentate ligand was used for complexation with Hg(II), UO₂(II), Au(III), Pt(IV) Mg(II), Bi(III), Sb(III) and Be(II) ions. The chelates were characterized by their analysis, molar conductance and infrared spectra. T.L.C. detection, separation and determination of these complexes on starch bound silica gel layers was studied Long persisting dark coloure of the complexes rendered the spots self descernible and no locating agent was required. A maximum four complexes could be resolved and identified. Errors in determinations and maximum separation limits were also deduced.     

Silica gel modified with N-(3-propyl)-O-phenylenediamine: functionalization, metal sorption equilibrium studies and application to metal enrichment prior to determination by flame atomic absorption spectrometry.

The use of the chemically modified silica gel N-(3-propyl)-O-phenylenediamine (SiG-NPPDA) adsorbent, for the preconcentration and separation of trace heavy metals, was described. SiG-NPPDA sorbs quantitatively (90-100% recovery) trace amounts of nine heavy metals, viz., Cd(II), Zn(II), Fe(III), Cu(II), Pb(II), Mn(II), Cr(III), Co(II) and Ni(II) at pH 7-8. The sorption capacity varies from 350 to 450 micromol g(-1). Desorption was found to be quantitative with 1-2 M HNO3 or 0.05 M Na2EDTA. The distribution coefficient, Kd and the percentage concentration of the investigated metal ions on the adsorbent at equilibrium, C(M,eqm)% (Recovery, R%), were studied as a function of experimental parameters. The logarithmic values of the distribution coefficient, log Kd, ranges between 4.0 and 6.4. Some foreign ions caused little interference in the preconcentration and determination of the investigated nine metals by flame atomic absorption spectrometry (AAS). The adsorbent and its formed metal chelates were characterized by IR (absorbance and/or reflectance), potentiometric titrations and thermogravimetric analysis (TGA and DTG). The mode of chelation between the SiG-NPPDA adsorbent and the investigated metal ions is proposed to be due to the reaction of the investigated metal ions with the two nitrogen atoms of the SiG-NPPDA adsorbent. The present adsorbent coupled with flame AAS has been used to enrich and determine the nine metal ions in natural aqueous systems and in certified reference materials (RSD < or = 5%). The copper, iron, manganese and zinc present in some pharmaceutical vitamin samples were also preconcentrated on SiG-NPPDA adsorbent and determined by flame AAS (RSD < or = 4.2%). Nanogram concentrations (0.07-0.14 ng ml(-1)) of Cd(II), Zn(II), Fe(III), Pb(II), Cr(III), Mn(II), Cu(II), Co(II) and Ni(II) can be determined reliably with a preconcentration factor of 100.     

Thin Layer Chromatography of Metal Ions Complexed with Anils (VII) Detection,Separation, and Determination

Abstract

Dark colored chelates of p-dimethylaminoanil of 3-benzoyl-methylglyoxal bidentate ligand with Sb(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), ZrO(II), Y(III), La(III), Pr(III), Nd(III) Sm(III), Gd(III) and Dy(III) have been chromatographed on starch bound silica gel thin layers. New correlations of I.R. with R_f (resolving solvent) have been used to ascertain the colored spots.

Among various mixtures resolved qualitatively a few typical ones have been alanysed quantitatively. Errors in determinations and maximum separation limits have also been deduced.     

Resacetophenone oxime–formaldehyde resin and its metal chelates. III

In this paper the synthesis and properties of resacetophenone oxime–formaldehyde resin are described. The number-average molecular weights of the resin determined by vapor-pressure osmometry and nonaqueous conductometric titration are 2200 ± 10% and 2500 g/mol, respectively. Cu(II), Ni(II), and Co(II) chelates of the resin were prepared. Elemental analysis of the chelates indicates a metal to ligand ratio of 1:2. The diffuse reflectance spectra and magnetic moments of Ni(II) and Co(II) chelates show tetrahedral structure, whereas Cu(II) chelate shows a square planar structure. Infrared spectral studies show that the metals are coordinated through the nitrogen of the oximino group and oxygen of the phenolic group. The presence of methylene bridges is also indicated by IR spectral studies. The thermal behavior of the resin and its metal chelates are also discussed.     

Gas Chromatography of Transition Metal Salicylaldimine Complexes

Abstract

The stability and ease of formation of some neutral salicylaldimine transition metal complexes has suggested that they may be gas chromatographed and find analytical applications. Thermal an of some bidentate Ni(II), Cu(II) and Zn(II) salicylaldimine comp has shown them to be thermally stable and volatile. Observations the gas chromatographic separation of some of these chelates is described, their favorable properties allow elution from glass a stainless steel columns with minimal decomposition under favorable conditions.     

Use of an o-aminobenzoic acid-functionalized XAD-4 copolymer resin for the separation and preconcentration of heavy metal(II) ions

XAD copolymer resins may be functionalized with heavy metal ion-selective ligands either by covalent linkage to the polymer backbone or by impregnation. These resins may be tailored to be specific for certain heavy metals by adjusting the adsorption and elution parameters, thereby enabling simple and cost-effective spectrophotometric and flame atomic absorption spectrometry (FAAS) determinations of these metals without requiring the more sophisticated coupled instrumental techniques. For the synthesis of o-aminobenzoic acid (ABA)-immobilized XAD-4 copolymer resin that is expected to preconcentrate a number of transition and heavy metals, the azo-linkage method was chosen. For this purpose the copolymer was nitrated, reduced to the corresponding amine, converted to the diazonium salt with nitrite, and reacted with o-aminobenzoic acid to produce the XAD-ABA sorbent. This sorbent was capable of preconcentrating Pb(II), Cd(II), Ni(II), Co(II) and Zn(II) from weakly acidic or neutral aqueous solution. The retained metals were eluted with 1.0 M HNO₃ from the resin column, and were subsequently determinated with by flame atomic absorption spectrometry. The developed resin preconcentration and determination method was successfully applied to the analysis of a synthetic metal mixture solution, a certified reference material (CRM) of coal sample, and brackish lake water.     

Preparation and reactivity of metal-containing monomers

The stability of chelates of several bivalent metals with poly(methacryloylacetone) was determined by pH titration. Two models in which the fragment of a polymeric molecule in the coordination sphere of a metal was approximated by either a mono- or a bidentate ligand were considered. Different mechanisms of complex formnation were realized depending on the nature of M(II).For part 29 seeIzv. Akad. Nauk, Ser. Khim., 1993, 975 [Russ. Chem. Bull., 1993,42, 937 (Eng.Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1063–1066, June, 1993.     

Building [2]Catenanes around a Tris(diimine)ruthenium(2+) ([Ru(diimine)3]2+) Complex Core Used as Template

In the course of the last two decades, the use of transition metals as templates for constructing catenanes has almost exclusively been restricted to tetrahedral copper(I). The present work is dealing with an octahedral metal, ruthenium(II), coordinated to three bidentate chelates. Incorporation of two chelates (1,10‐phenanthroline) in a ring allows to prepare a C₂‐symmetric ruthenium complex, the two chelates being disposed cis to one another (see 14 ²⁺ and 16 ²⁺ in Scheme 5 and 6, resp.). The ring is large enough to accomodate a third chelate, thus allowing the metal‐directed threading of a long fragment containing the third chelate (2,2′‐bipyridine derivative; see 23 ²⁺ and 24 ²⁺ in Scheme 8). The last step consists of a ring‐closing metathesis reaction with two terminal olefins. The two ruthenium(II)‐complexed catenanes 25 ²⁺ and 26 ²⁺ were prepared by using this strategy, each containing a 42‐membered ring interlocked to a larger macrocycle (50‐ or 63‐membered ring) incorporating the two 1,10‐phenanthroline chelates. It is expected that these catenanes can be set in motion under light‐irradiation, thus behaving as photochemically driven molecular machines.