The Triple Complexes of Copper and its Complexes with the Schiff Bases of Pyridine-2-Aldehyde or 2-Acetyl Pyridine with Aliphatic Diamines

When alcohol solutions of copper salts are mixed with pyridine-2-aldehyde (PyA) and aliphatic diamines (A) (either ethylene diamine or 1,3-propane diamine) at pH ≤ 6.5, a copper complex containing a molecule of the pyridine derivative and a molecule of the diamine is formed, or a complex containing an additional molecule of the pyridine aldehyde is formed, depending on the PyA concentration in the solution. When the molar concentrations are Cu²⁺: 2PyA: A, and the pH ≥ 10, the copper (II) ion is reduced to monovalent copper, and a Schiff base of the copper complex is formed. When alcoholic solutions of copper, 2-acetylpyridine (AcPy), and aliphatic diamines are mixed in concentration ratios of Cu²⁺: 2AcPy: A, and pH > 9.5, again, the copper ion is reduced and a Schiff base is obtained. At pH = 7.5 a triple complex is obtained only from the copper chloride, containing either or one or two molecules of acetylpyridine, depending on the concentration of the latter in the solution.     

Preparation of functionalized ion‐imprinted phenolic polymer for efficient removal of copper ions

In this work, an ion‐imprinted polymeric material based on functionalized phenolic resin was developed for the efficient selective removal of Cu²⁺ ions from aqueous solution. p‐Aminophenol‐isatin Schiff base ligand (HPIS) was first synthesized and combined with Cu²⁺ ions to prepare the corresponding complex [Cu(PIS)₂]. The Schiff base ligand along with its copper complex was fully investigated and characterized before anchoring in a base‐catalyzed condensation copolymerization with formaldehyde and resorcinol. The Cu²⁺ ions were removed from the obtained resin construction and the resulting Cu²⁺ ion‐imprinted material (Cu‐PIS) was employed for the selective extraction of Cu²⁺ ions under different pH values, initial concentrations and contact time conditions. The optimum pH for the removal process was chosen as 6 and the maximum adsorption capacity was 187 ± 1 mg g^–1. Also, the kinetics showed a better fit with the pseudo‐second‐order equations. The selectivity of the prepared Cu‐PIS was also evaluated in a multi‐ionic species containing Ni²⁺, Cd²⁺, Pb²⁺, Co²⁺ besides Cu²⁺ ions and the determined parameters confirmed a superior recognition capability toward the imprinted Cu²⁺ ions. © 2019 Society of Chemical Industry     

Synthesis and characterization of new bis(crown ether)s of Schiff base type containing recognition sites for sodium and nickel guest cations

New bis(crown ether) ligands of Schiff base type ( 2 – 4 ) containing recognition sites for sodium and nickel guest cations have been synthesized by the condensation of two equivalents of 4′-formyl-5′-hydroxy(benzo-15-crown-5) ( 1 ) with diamines, H₂N–(CH₂)_n–NH₂(n = 2–4). Homonuclear ditopic crystalline 2 : 1 (Na⁺ : ligand) complexes ( 2a – 4a , 2b – 4b ) of the ligands with NaSCN and NaClO₄ have been prepared. The NaClO₄ complexes of 3 and 4 ( 3b and 4b ) form heteronuclear tritopic crystalline complexes with Ni²⁺ cations of stoichiometry 2 : 1 : 1 (Na⁺ : Ni²⁺ : ligand). A homonuclear monotopic Ni²⁺ complex has also been prepared by the reaction with Ni(CH₃COO)₂ · 6H_2O. The UV-VIS spectra of 2 – 4 and their NaClO₄ complexes ( 2b – 4b ) are studied in different solvents including acidic and basic media. In polar solvents, tautomeric equilibria (phenol–imine, O–H…︁N and ketoamine, O…︁H–N forms) are present, as supported by the UV-VIS data.     

Synthesis and characterization of Schiff‐base‐containing polyimides

Benzyl bisthiosemicarbazone and its complexes with nickel (NiLH₄) and copper (CuLH₄) were used as diamine monomers for the synthesis of new Schiff‐base polyimides. The solution polycondensation of these monomers with the aromatic dianhydrides afforded metal‐containing Schiff‐base polyimides with inherent viscosities of 0.98–1.33 dL/g (measured in N‐methyl‐2‐pyrrolidone at 25°C). The polyimides were generally soluble in a wide range of solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, tetrachloroethane, hexamethylene phosphoramide, N‐methyl‐2‐pyrrolidone, ethyl acetate, and pyridine at room temperature. The initial degradation temperatures of the resultant polyimides fell in the range of 220–350°C in nitrogen with char yields ranging from 36 to 64% at 700°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The Copper (II) Complexes of Phenyl-2 Pyridyl Ketone and the Triple Complexes Obtained by Adding Ethylenediamine

Copper salts of low pH (1.8–2.5) combine with phenyl-2-pyridyl ketone to form a ketone complex [(Py–CO–C₆H₅)₂Cu]²⁺. An electrically uncharged complex is obtained at pH > 9 [(Py–C(OH)(C₆H₅)O^?)₂Cu]⁰, liberating two protons from two molecules of the ligand. The stability constant of this complex is β = 16.05. By mixing the copper salts (except the halide) containing this ligand with ethylenediamine, a charged triple complex is obtained at pH < 7 [Py–C(OH)(C₆H₅) O–Cu–NH₂C₂H₄NH₃⁺]²⁺. At pH > 9.5, an uncharged triple complex is obtained: {[(Py–C(OH)(C₆H₅)O^?)₂Cu}₂ · NH₂C₂H₄NH₂}⁰. The copper halide salts produce only an uncharged triple complex; the halide ions are coordinated with the copper atoms. All of these complexes in their solid state, are bi- or polynuclear. As a result, they are magnetically subnormal.     

Nanodimensional microreactors encapsulation of 15- and 16-membered diaza dioxa macrocyclic Schiff-base copper(II) complex nanoparticles: Synthesis and characterization

Copper(II) complexes with 15- and 16-membered diaza dioxa Schiff-base macrocyclic ligands “[Cu(R[15 or 16]N₂O₂)]²⁺ (R = Et, Pr, Ph, Ch)” were entrapped in the nanopores of zeolite-Y by a three-step process in the liquid phase: (i) exchange of Cu(II) ions with NaY in water solution, (ii) reaction of Cu(II)–NaY with excess 1,3-bis(2-carboxyaldehydephenoxy)propane (O₂O₂) in methanol, [(1,3-bis(2-carboxyaldehydephenoxy)propane)copper]²⁺@NaY, [Cu(O₂O₂)]²⁺@NaY (iii) template synthesis of [Cu(O₂O₂)]²⁺@NaY with diamine. The obtained new complex nanoparticles entrapped in the nanopores of zeolite Y have been characterized by elemental analysis FT-IR, XPS, DRS, UV–vis spectroscopic techniques, molar conductance, magnetic moment data, XRD and nitrogen adsorption. Analysis of data indicates all of the complexes have been encapsulated within nanopores without affecting the zeolite framework structure.     

Removal of Copper(II) from a Concentrated Sulphate Medium by Cloud Point Extraction Using an N,N′-Bis(salicylaldehyde)Ethylenediimine Di-Schiff Base Chelating Ligand

Various chelating ligands have been investigated for the cloud point extraction of several metal ions. However, limited studies on the use of the Schiff base ligands have been reported. In this work, cloud point extraction behavior of copper(II) with N,N′‐bis(salicylaldehyde)Ethylenediimine Schiff base chelating ligand, (H₂SALEN), was investigated in aqueous concentrated sulphate medium. The extraction process used is based on the formation of hydrophobic H₂SALEN–copper(II) complexes that are solubilized in the micellar phase of a non‐ionic surfactant, i.e. ethoxylated (9.5EO) tert‐butylphenol. The copper(II) complexes are then extracted into the surfactant‐rich phase above cloud point temperature. Different parameters affecting the extraction process of Cu(II), such as equilibrium pH, extractant concentration, and non‐ionic surfactant concentration were explored. The extraction of Cu(II) was studied in the pH range of 2–11. The results obtained showed that it was profoundly influenced by the pH of the aqueous medium. The concentration factor, C_f, of about 17 with extraction efficiency of E % ≈100 was achieved. The stoichiometry of the extracted complex of copper(II) was ascertained by the Yoe–Jones method to give a composition of 1:1 (Cu:H₂L). The optimum conditions of the extraction‐removal have been established as the following: (1) 1.86 × 10^?3 mol/L ligand; (2) 3 wt% surfactant; (3) pH of 8 (4) 0.5 mol/L Na₂SO₄ and (5) temperature of 60 °C.     

A mononuclear copper(II) complex of a protonated unsymmetrical dinucleating Schiff base ligand

Reaction of the unsymmetrical and potentially dinucleating Schiff base ligand HL¹ with copper(II) salts has given mono- and dinuclear metal complexes. The structure of a mononuclear complex of diprotonated HL¹, [Cu(H₂L¹)(OH₂)](ClO₄)₃·H₂O·CH₃OH_, has been determined.     

Synthesis and characterization of novel Schiff‐base polyamides from copper/benzil bisthiosemicarbazone complexes

A new copper‐containing Schiff‐base diamine, benzil bis(thiosemicarbazonato)copper(II) (CuLH₄), was synthesized in two steps from benzil bisthiosemicarbazone (LH₆). The ligand LH₆ and the complex CuLH₄ were characterized with Fourier transform infrared spectroscopy, ¹H‐NMR, and elemental analysis. CuLH₄ was used to prepare novel polyamides. The low‐temperature solution polycondensation of the complex CuLH₄ with various aromatic and aliphatic diacid chlorides afforded copper‐containing Schiff‐base polyamides with inherent viscosities of 0.25–0.36 dL/g in N,N‐dimethylformamide (DMF) and 0.75 dL/g in H₂SO₄ at 25°C. The polyamides were generally soluble in a wide range of solvents, such as DMF, N,N‐dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, ethyl acetate, tetrachloroethane, hexamethylene phosphoramide, N‐methylpyrrolidone, and pyridine. Thermal analysis showed that these polyamides were practically amorphous, decomposed above 270°C, and exhibited 50% weight loss at and above 400°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structural evidence of a ketimine as the product of an amino acid with an aldehyde. An intermediate in the racemization and transamination of amino acids

The aldimine and ketimine forms of two Schiff base complexes formed by the condensation of two isomeric imidazole carboxaldehydes with an amino acid are reported. Reaction of L¹, the Schiff base condensate of 5-methyl-4-imidazolecarboxaldehyde (5Me4Im) and valine, with copper(II) perchlorate results in the isolation of [Cu(L¹)(5Me4Im)(ClO₄)] while the analogous reaction of L², the Schiff base condensate of 1-methyl-2-imidazolecarboxaldehyde (1Me2Im) with alanine, and nickel(II) results in the isolation of [Ni(L²)₂]. L¹ exhibits the expected aldimine form of the amino acid derived Schiff base, 5Me4Im-CH = N-CH(R)CO₂⁻, while L² exhibits the tautomeric ketimine form, 1Me2Im-CH₂–N = C(R’)CO₂⁻. Structural data clearly support the two tautomeric forms. The ketimine form, observed in [Ni(L²)₂], has been proposed as an intermediate in the racemization and transamination of amino acids.     

Polymer‐immobilized N,N′‐bis(acetylacetone)ethylenediamine cobalt(II) Schiff base complex and its catalytic activity in comparison with that of its homogenized analogue

For the preparation of a heterogenized N,N′‐bis(acetylacetone)ethylenediamine cobalt(II) Schiff base complex, first crosslinked polymer beads were prepared by the suspension copolymerization of styrene (48.97 mmol, 5.1 g), allyl chloride (48.97 mmol, 3.746 g), and divinyl benzene (DVB; 1.75 mmol, 0.228 g) in the presence of azobisisobutyronitrile (0.9 × 10^?3 mmol, 0.15 g) as an initiator at 23 ± 0.1°C under an inert atmosphere. The copolymerization of styrene, allyl chloride in the presence of gelatin (0.75 g), bentonite (2.0 g), and boric acid (2.5 g) produced beads of different crosslinked densities corresponding to the concentration of DVB in the reaction mixture. The amount of allyl chloride in the prepared beads varied from 5.40 to 7.40 mmol g^?1 of beads with the amount of DVB varying from 2.0 to 0.8 mmol in the reaction mixture. A quadridentate Schiff base (acen) was prepared with ethylenediamine (5.0 mmol, 0.3 g) and acetylacetone (10.0 mmol, 1.0 g), and it was used to obtain a homogenized and heterogenized Co(II)(acen)₂ complex. The extent and arrangement of the Schiff base (acen) in the crosslinked beads depended on the availability of DVB in the reaction mixture. The amount of DVB in the reaction mixture influenced the extent of cobalt(II) ion loading, the degree of swelling, the porosity, and the pore size in the prepared beads. The beads (type IV) prepared with 1.75 mmol (0.228 g) of DVB in the reaction mixture showed a degree of swelling of 9.65% and efficiencies of loading and complexation for cobalt(II) ions of 49.4 and 85%, respectively, in comparison with beads obtained at other concentrations of DVB in the reaction mixture. The structure of free and polymer‐supported Co(II)(acen)₂ complexes was verified with IR, UV, and magnetic measurements, which suggested a square planar geometry for the complexes under both conditions. The catalytic activities of the homogenized and heterogenized Co(II)(acen)₂ complexes were compared by the evaluation of the rate constant (k) for the decomposition of hydrogen peroxide. The heterogenized Co(II)(acen)₂ complex showed a high catalytic activity for the decomposition of hydrogen peroxide (k = 2.02 × 10^?4 s^?1) in comparison with the homogenized Co(II)(acen)₂ complex (k = 4.32 × 10^?6 s^?1). The energy of activation for the decomposition of hydrogen peroxide with the heterogenized Co(II)(acen)₂ complex was low (38.52 kJ mol^?1) in comparison with that for the homogenized complex (73.44 kJ mol^?1). In both cases, the rate of decomposition of hydrogen peroxide was directly proportional to the concentration of hydrogen peroxide and cobalt(II) ions. On the basis of experimental observations, a rate expression for the decomposition of hydrogen peroxide was derived. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1398–1411, 2003     

Stepwise synthesis of a pentanuclear copper(II)–manganese(II) cluster by using a versatile Schiff base ligand derived from 3-formylsalicylic acid

The Schiff base 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid (H₂L) is a useful ligand for the design of heteronuclear complexes. A pentanuclear copper(II)–manganese(II) cluster was synthesized by using H₂L as a ligand. The compound was characterised by analytical and spectral methods. Cryomagnetic investigations over the temperature range 1.9–300 K reveal antiferromagnetic interactions between the copper(II) and manganese(II) ions.     

Polystyrene anchored vanillin Schiff base—Complexation and ion removal studies

A set of six new polystyrene anchored metal complexes have been synthesized by the reaction of the metal salt with the polystyrene anchored Schiff base of vanillin. These complexes were characterized by elemental analyses, Fourier transform infrared spectroscopy, diffuse reflectance studies, thermal studies, and magnetic susceptibility measurements. The elemental analyses suggest a metal : ligand ratio of 1 : 2. The ligand is unidentate and coordinates through the azomethine nitrogen. The Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes are all paramagnetic while Zn(II) is diamagnetic. The Cu(II) complex is assigned a square planar structure, while Zn(II) is assigned a tetrahedral structure and Mn(II), Fe(III), Co(II), and Ni(II) are all assigned octahedral geometry. The thermal analyses were done on the ligand and its complexes to reveal their stability. Further, the application of the Schiff base as a chelating resin in ion removal studies was investigated. The polystyrene anchored Schiff base gave 96% efficiency in the removal of Ni(II) from a 20‐ppm solution in 15 min, without any interference from ions such as Mn(II), Co(II), Fe(III), Cu(II), Zn(II), U(VI), Na⁺, K⁺, NH₄⁺, Ca²⁺, Cl^?, Br^?, NO₃^?, NO₂^?,and CH₃CO₂^?. The major advantage is that the removal is achieved without altering the pH. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1536–1539, 2005     

Synthesis and X-ray crystal structure of monomeric lanthanocene aryloxide complexes with a tridentate Schiff base ligand

Reaction of tris(cyclopentadienyl)lanthanide with the tridentate Schiff base N-1-(ortho-methoxyphenyl)salicylideneamine in THF at room temperature affords the isolation of monomeric lanthanocene Schiff base complexes, (η⁵-C₅H₅)₂Ln (OC₁₄H₁₃NO) (Ln=Sm (1), Er (2), Dy (3), Y (4)), which have been characterized by elemental analysis and mass spectra. The X-ray determination of 1 indicates that the complex is monomeric in which the metal center is coordinatively saturated by two cyclopentadienyl rings and two oxygens and one nitrogen from the Schiff base ligand. The average Sm–C bond distance is 2.723(7) Å, while those of the metal center to the Schiff base oxygens and nitrogen atoms are 2.232(4), 2.572(4) and 2.534(4) Å, respectively.     

Synthesis,crystal structures and NIR luminescence properties of binuclear lanthanide Schiff Base complexes

Three binuclear lanthanide complexes [Nd₂(L¹)₃(MeOH)]·MeOH·H₂O (1) and [Ln₂(H₂L²)₂(OAc)₄]·2(CF₃SO₃)·MeOH·EtOH (Ln = Nd (2) and Ho (3)) were prepared using two Schiff base ligands. Interestingly, 1 has a triple-decker structure with two lanthanide ions enclosed by three rigid conjugated Schiff base ligands (H₂L¹), while 2 and 3 show nanoscale ring structures (8 × 12 × 12 Å) formed by flexible long-chain Schiff base ligands (H₂L², ~ 23 Å) with the lanthanide ions located in the center. Upon excitation of the ligand-centered absorption bands, 1–2 and 3 show typical NIR emission spectra for Nd^3 + and Ho^3 + ions, respectively. In 1, the Nd(III) centers are shielded within the decker-like structure and surrounded by chromogenic Schiff base ligands (energy transfer donors). Luminescence studies show that the NIR emission lifetime of 1 is longer than that of 2 in solution.     

Removal of Ag(l), Cu(II) and Zn(ll) ions with a supported liquid membrane containing cryptands as carriers

The interface behaviour in the facilitated co-transport of Ag(I), Cu(II) and Zn(II) ions through supported liquid membranes (SLMs) made of a flat-sheet polypropylene membrane support containing cryptands (2.2.2 or 2.2.1) as carriers was studied. The liquid-liquid extraction tests showed a maximum distribution coefficient when the carrier concentration was greaterthan 10⁻⁴M. In transport experiments the transmembrane flux increased with increasing carrier concentration reaching a limiting value at greater than 10⁻³M concentration. The calculation ofthe diffusion coefficients in membranes showed ahigherdiffusivityof2.2.2-metal complexes with respect to 2.2.1-metal complexes for silver ions. A sequence of diffusivity D(Ag+)>D(Cu²⁺)>D(Zn²⁺) was obtained, but carrier 2.2.1 showed a higher selectivity through copper ions. A sequence of diffusivity D(Cu²⁺)>D(Zn²⁺)>D(Ag⁺) was obtained. The diffusivity was significantly higher when using Celgard 2500 support compared to Celgard 2400 or 2402. Variable metal ion concentrations in the feed phase fluxes almost zero, at less than 10⁻² M concentration, were obtained. In the transient state of the transport through the SLM, different molar flow rates at the feed-membrane and membrane-strip interfaces were observed. The selectivity of the interfaces containing 2.2.2 in the separation binary mixtures of ions showed the following separation factors: SF_AgZn = 2.50, SF_AgCu = 1.64, SF_cuZn = 1.42.     

Soluble and insoluble ternary complexes of serum proteins with polyanions in the presence of Cu2+ in water

Complex formation between polyacrylic acid (PAA) and bovine serum albumin (BSA), human serum albumin (HSA), hemoglobin (Hb), globin (Gl), and, respectively, transferrin (Tr), were studied in neutral water. Water-soluble and insoluble complexes are formed upon addition of divalent copper ions to the solution. The contacts between proteins and PAA are achieved via chelate unit formation in which the copper ions are located at the center. The solubility of the polycomplexes depends on the nature of proteins and correlates with their isoelectric points (pI). In the mixtures of Hb–Cu²⁺–PAA and Gl–Cu²⁺–PAA, insoluble complexes are formed at pH = pI starting with very low concentrations of Cu²⁺ (n_cu/n_AA ≤ 0.01). On the other hand, these polycomplexes remain soluble at pH > pI. BSA, HSA, and Tr form soluble ternary polycomplexes at neutral water (pH 7). The formation of the polycomplexes in the mixture BSA&–Cu²⁺–PAA was intensively studied by titration, HPLC, electrophoretic, and spectrophotometric methods. The solubility, composition, and stability of these polycomplexes depend on metal/polymer and protein/polymer ratio. Insoluble polycomplexes are formed when concentration of Cu²⁺ reaches a critical value (n_Cu/n_AA ≥ 0.25). At this concentration of Cu²⁺, phase separation takes place, starting with very low concentration of protein in the system. Over the critical ratio of the protein/polymer, the mixture again exhibits water-soluble character. The pattern of distribution of Cu²⁺ between PAA coils and of protein globules between polymer-metal complex particules appeared to follow the self-assembly principle. A hypothetical structural scheme for the formation of soluble and insoluble ternary polycomplexes is proposed. © 1996 John Wiley & Sons, Inc.     

Theoretical and practical investigations of copper ion selective electrode with polymeric membrane based on N,N′-(2,2-dimethylpropane-1,3-diyl)-bis(dihydroxyacetophenone)

A novel ion-selective poly(vinyl chloride) (PVC) membrane sensor for Cu²⁺ ions based on N,N′-(2,2-dimethylpropane-1,3-diyl)-bis(dihydroxyacetophenone) (NDHA) as a new ionophore was prepared and studied. The best performance was observed for the membrane composition, including 30:65:1:4 (wt%) = PVC:DBP:KTpClPB:NDHA. The electrode showed a good Nernstian slope of 30.0 ± 0.5 mV/decade in a wide linear range activity of 3.0 × 10⁻⁷ to 1.0 × 10⁻² mol dm⁻³ Cu(NO₃)₂ with limit of detection 2.5 × 10⁻⁷. Sensor exhibited a fast response time (t_95% < 10 s) and could be used for about 4 months in the pH range of 3.0–7.4. The proposed potentiometric sensor was found to work satisfactorily in partially non-aqueous media up to 30 (vol%) content of methanol, ethanol and acetone. Applications of this electrode for the determination of copper in real samples, and as an indicator electrode for potentiometric titration of Cu²⁺ ion using EDTA, were reported. In order to predict the extraction ability of NDHA for different metallic ions, the complexes [M(NDHA)] and [M(H₂O)₆] (where M = Cu²⁺, Co²⁺, Hg²⁺, Pb²⁺, Ag⁺, Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cd²⁺, K⁺ and Al³⁺) were investigated using ab initio theoretical calculations. The metal binding capability was evaluated using the binding energy. Results of our study could be useful for prediction of the extraction power of this Schiff base and could play a guiding role in planning experiments.     

Structure and magnetic properties of A Cu(II) coordination polymer supported by a tetrapodal Schiff base ligand

A Cu(II) Schiff base coordination polymer, {[Cu₃L(μ₂-NO₃)₂·(H₂O)₂].3H₂O}_n, is readily prepared by complexation of the tetrapodal Schiff base, H₄L (H₄L = 1,1,1,1-tetrakis[(salicylaldimino)methyl]methane), with cupric nitrate trihydrate. It has been demonstrated that the coordination polymer consists of linear trinuclear Cu(II) entities, and displays a cooperative coordination mode for nitrate anions, coordinated water molecules, and Schiff base ligands to Cu(II) ions. In addition, variable-temperature magnetic susceptibility measurements reveal a strong antiferromagnetic coupling interaction between adjacent copper(II) ions with large J value of − 289.66 cm^− 1.     

Application of FTIR spectroscopy for structural characterization of ternary poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

The FTIR spectroscopic technique was used in the study of ternary polymer–metal complexes containing two polyelectrolytes of opposite charge and metal ions. The structure of the ternary (PAA‐Fe³⁺‐PVP) complexes was examined by following the changes in their infrared spectra. It was found that the shapes of the absorption bands of the resultant compounds are influenced by the presence of Fe³⁺. According to this result it was suggested that two types of structure which differ in the composition are formed, one of which results from the coordination of Fe³⁺ with PAA‐PVP complex and the other is due to the formation of Fe³⁺ polycarboxylate. Comparison between the spectrum of PAA‐PVP complex and those of the compounds resulted from the reaction between the two opposite charged electrolytes, PAA and PVP and each of the divalent metal chlorides NiCl₂, CoCl₂, CuCl₂, and ZnCl₂) led to the conclusion that a reaction took place between the divalent transition metal chlorides and the extent of reaction depends on the nature of metal ions and PAA‐PVP complex. The FTIR spectra of the precipitate resulted from the mixtures of PAA‐PVP and Ni(NO₃)₂ or Sr(NO₃)₂ were investigated. It was noted that the addition of Ni(NO₃)₂ or Sr(NO₃)₂ to the mixture of the electrolytes of PAA and PVP provoked appreciable changes in the characteristic spectral features of the complex resulting from the interaction of the metal ions with the polymer–polymer complex. The FTIR spectra of the precipitate resulted from the reaction between CeCl₃, ErCl₃, and LaCl₃ were also investigated. It was concluded that a reaction took place between the rare earth metals and the PPC. This means that ternary polymer–metal–polymer complexes were formed. The extent of changes in the spectral features differs from metal to metal according to the nature of metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2007