Potentiometric study of the Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with 3-hydroxy-2-naphthalene carboxylic acid

Formation constants of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with 3-hydroxy-2-naphthalene carboxylic acid have been determined potentiometrically in a 50% (v/v) dioxane—water solution at 25°C and 0.2 M KNO₃. Experimental data are analysed using several computer programs. The obtained values for the log of the formation constant of the first 1 : 1 (metal : ligand) complex with the different metals are: Co 7.9, Ni 7.1, Cu 10.44, Zn 7.8 and Cd 7.3. The log of the formation constant for the 1 : 2 copper complex is 18.20. It is to be noted that Ni(II) yields a 1 : 1 complex weaker than expected from the Irving—Williams series.     

A potentiometric study of the complexes formed between Ni(II) and Zn(II) and 3-mercaptopropionic acid

The composition and stability constants of the complexes formed between Ni(2+) and Zn(2+) and 3-mercaptopropionic acid (3-MPA) were studied by a potentiometric method at 25 degrees and in 0.5M KNO(3). For the system Zn(2+)/3-MPA. a mixture of the mononuclear complex BA(2) and the polynuclear complexes B(3)A(4). and B(4)A(6) was found (B means the metal ion and A the ligand). The system Ni(2+)/3-MPA can be represented by the complexes B(5)A(10), B(6)A(11) B(6)A(9) and B(6)A(12). In this series the last two complexes are predominant.     

Polarographic study of the dipropyldithiophosphinate complexes of Pd(II), Pb(II), Cd(II), and Zn(II) ions

The complexes of the dithiophosphinic acids with Pd(II), Pb(II), Cd(II), and ZN(II) in a toluene-ethanol medium produce single polarographic waves. The half-wave potential is a linear function of the ligand concentration. The stabilities of these chelates, which are characterized by a sulphur-metal bond, are in the order: Pd(II) > Pb(II) > Cd(II) > Zn(II).     

Orotic acid complexes of Co(II), Ni(II), Zn(II) and Cd(II) with imidazole

The [Co(HOr)(H₂O)₂(im)₂] (1), [Ni(HOr)(H₂O)₂(im)₂] (2), [Zn(H₂O)₂(im)₄](H₂Or)₂ (3) and [Cd(HOr)(H₂O)(im)₃] (4) complexes (H₃Or: orotic acid, im: imidazole) were synthesized and characterized by elemental analysis, magnetic and conductance measurements, UV-vis and IR spectra. The thermal behaviour of the complexes was also studied by simultaneous thermal analysis techniques (TG, DTG and DTA). The orotate ligand (HOr²⁻) coordinated to the Co(II), Ni(II) and Cd(II) ions are chelated to the deprotonated pyrimidine nitrogen (N₍₃₎) and the carboxylate oxygen, while do not coordinate to the Zn(II) ion is present as a counter-ion (H₂Or⁻). The first thermal decomposition process of all the complexes is endothermic deaquation. This stage is followed by partially (or completely) decomposition of the imidazole and orotate ligands. In the later stage, the remained organic residue exothermically burns. On the basis of the first DTG_max, the thermal stability of the complexes follows order: 2, 176°C>1, 162°C>4, 155°C>3, 117°C in static air atmosphere. The final decomposition products which identified by IR spectroscopy were the corresponding metal oxides.     

The polynuclear complex formation between lead (II) and 2-mercaptoethanol reinvestigated

The termodynamics of complex formation between lead (II) and 2-mercaptoethanol has been rein-vestigated at I = 150 mmol dm⁻³ NaNo₃ and at lower metal: ligand ratios in order to determine the mononuclear formstion constants.     

Spectrophotometric study of Cd(II), Pb(II), Hg(II) and Zn(II) complexes with 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin

The reaction of 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) with Cd(II), Pb(II), Hg(II) and Zn(II) was studied spectrophotometrically and kinetics, equilibrium constants as well as photodecomposition of complexes were determined. It was verified that these metal ions with large radius accelerate the incorporation reaction of zinc into TCPP. On the basis of the mechanism and kinetics of this reaction, a sensitive method for the spectrophotometric determination of trace amounts of Zn(II) has been developed. The molar absorptivity of examined Zn-TCPP complex and Sandell's sensitivity at 423 nm were 3.5×10⁵ M⁻¹ cm⁻¹ and 18.3 ng cm⁻². The detection limit for the recommended procedure was 1.4×10⁻⁹ M (0.9 ng ml⁻¹) and precision in range 20-100 ng ml⁻¹ not exceeds 2.7% RSD. The proposed method applied for zinc determination in natural waters and nutritional supplement was compared with AAS results and declared value.     

Studies on ion association. Calorimetric study of the formation of monoazido complexes of Ni(II), Zn(II) and Cd(II)

From rehydration experiments the hydrates Ba(OH)₂ · 8 H₂O, Ba(OH)₂ · 3 H₂O β-Ba(OH)₂, · 1 H₂O, and γ-Ba(OH)₂ · 1 H₂O have been found in the system Ba(OH)₂-H₂O. Thermoanalytical measurements (DTA, TG, DTG, high temperature X-ray diffraction, high temperature Raman scattering) on these hydrates are reported. Thermal decomposition of Ba(OH)₂ · 8 H₂O and Ba(OH)₂ · 3 H₂O always results in the formation of β-Ba(OH)₂ · 1 H₂O, the stable form of the monohydrates at ambient temperature. Dehydration of β- and γ-Ba(OH)₂ · 1 H₂O, both of which form anhydrous β-Ba(OH)₂ as the first product of decomposition, starts at 105 and 115°C, respectively. Single crystals of Ba(OH)₂ · 3 H₂O and γ-Ba(OH)₂ · 1 H₂O were prepared from Ba(OH)₂ · 8 H₂O meltings and from ethanolic solutions of Ba(OH)₂ , respectively. The crystal data are: Ba(OH)₂ · 3 H₂O (orthorhombic, Pnma): a = 764.0(2), b = 1140,3(5), c = 596.5(1) pm, Z = 4; γ-Ba(OH)₂ · 1 H₂O (monoclinic, P2₁/m or P2₁): a = 704.9(2), b = 418.4(1), c = 633.3(1) pm, β = 111.45(2)°, Z = 2.     

Synthesis and characterization of Ni(II), Zn(II), and Cd(II) complexes with dithiophosphonate derivatives

Ammonium salts of p-methoxyphenyldithiophosphonic acid O-alkyl esters (H₃CO-C₆H₄-(RO)P(S)S⁻NH ₄ ⁺ ; R = C₂H₅,-CH₂CH₂CH₂CH₂-, and cyclopentyl) and their complexes with Ni²⁺, Cd²⁺, and Zn²⁺ were prepared. 2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide, the so-called Lawesson reagent, was treated with the corresponding alcohol to give the O-alkyl ester of the acid. Dry NH₃ was then purged through the solution of this ester to form the ammonium salt of the O-alkyl dithiophosphonic acids. Nickel complexes of these ligands were formed in acetic acid, while zinc and cadmium complexes were formed in water and an ethanol medium, respectively. The geometry of the coordinated atoms was square planar with Ni²⁺ and tetrahedral with Zn²⁺ and Cd²⁺. Using an alkanediol, two dithiophosphonic acids were bridged, thus forming a ligand with four S atoms for coordination. The zinc and cadmium complexes of these tetradentate ligands were also synthesized. The text was submitted by the authors in English.     

Spectroscopic and theoretical study of Cu(II), Zn(II), Ni(II), Co(II) and Cd(II) complexes of glyoxilic acid oxime

The paper presents a detailed experimental and theoretical study of five metal complexes of glyoxilic acid oxime (gaoH2), Cu(gaoH)2(H2O)2 (1), Zn(gaoH)2(H2O)2 (2), Co(gaoH)2(H2O)2 (3), Ni(gaoH)2(H2O)2 (4) and [Cd(gaoH)2(H2O)2].H2O (5). The electronic and vibrational spectra were measured and discussed as to the most sensitive to the M-L binding bands. Two different types of coordination were considered for gaoH- ligand: bidentate through the carboxylic oxygen and oxime nitrogen in 1-4 and mixed bidentate and bridging through the COO group in 5. It is shown that the spectral behavior of the nu(COO) modes can be used to predict bridging ligand coordination. DFT(B3LYP/6-31++G(d,p)) calculations on model compounds: neutral, anionic and radical forms of gao and Cu(gaoH)2, have been carried out to correlate geometries, electronic and vibrational structures. The results obtained were used to assist the electronic and vibrational analysis of the complexes studied. The effect of the metal-ligand interactions (electrostatic and covalent) on the geometry structure of the ligand was investigated.     

X-ray photoelectron spectra of complexes with 1-(D-3-mercapto-2-methylpropionyl)-L-proline and Ni(II), Cd(II) and Cu(I): synthesis and LAXS study of Cu(I) derivative

Metal complexes of general formula Na2M(CAP)2xH2O (with M = Cd(II) or Ni(II), x = 7 and 4, respectively, CAP = 1-(D-3-mercapto-2-methylpropionyl)-L-proline) and NaCuCAPx3H2O have been synthesized as amorphous compounds and studied by means of X-ray photoelectron spectroscopy (XPS). Cu(I) derivative has been studied by IR, XPS and large-angle X-ray scattering (LAXS). IR data and the chemical shift of core level signals suggest that CAP is bonded to the metal via the sulphur atom and the carbonylic oxygen. LAXS data confirm this finding and are consistent with a tetrahedral configuration around the copper ion. The CAP molecule is bonded through the sulphur and the carbonylic oxygen and two water molecules complete the coordination around the metal. The sodium ion exhibits a tetrahedral configuration and interacts with the carboxylic group and two water molecules. One of these is bridging bonded between copper and sodium. No metal-nitrogen bonds are present.     

Crystal structure of polynuclear pivalate Ni(II) complexes with butanediol

Using single crystal X-ray diffraction the structure of polynuclear [Ni₆(OH)₄(Piv)₇(HOC₄H₈O)(HPiv)₄], {K₄[Ni₁₂(CO₃)₂(Piv)₁₆(OH)₈(HOC₄H₈OH)₂]}HPiv, {[Ni₆(OH)₄(Piv)₆(HOC₄H₈O)(Me₂CO)(HOC₄H₈OH)₂]₄×(Piv)₄}, and {K[Ni₂L₂(Piv)₃]}_∞ complexes, where HOC₄H₈OH is 1,4-butanediol, HPiv is pivalic acid, and L is the anion of nitroxyl radical 2,2,5,5-tetramethyl-4-(3′,3′,3′-trifluoro-2′-oxy-1′-propenyl)-3-imidazolin-1-oxyl is determined.     

Formation of protonated salicylate complexes of Cd(II) and Zn(II)

The formation constants of the protonated complexes of Cd(II) and Zn(II) with salicylic acid (H₂Sal) and the equilibrium constants for the extraction of these complexes into cyclohexane containing tributyl phosphate (TBP) have been determined. For the complex formation:

log K₁₁ is 1.9 for Cd(II) and 1.4 for Zn(II) at 30°C and 0.1 M NaClO₄. For the extraction:

log K_ex is ?1.6 for Cd(1I) and ?2.2 for Zn(II).     

Noncovalent interactions of pentafluorobenzoate in the Zn(II) and Cd(II) complexes

[Zn(Phen)2(Pfbz)(H2O)](Pfbz)(H2O)2 (I) and 2[Cd(Phen)2(Pfbz)(ONO2)][Cd(Phen)2(ONO2)2] (II) (Phen-1,10-phtnanthroline) containing the fluorine type ligand, pentafluorobenzoate (Pfbz) have been synthesized. Elemental analysis, IR spectra, and X-ray crystal structure analysis were carried out to determine the compositions and crystal structures of the two compounds. The crystal packing exhibits intricate intermolecular π-π stacking interactions and various hydrogen bonds. The C-H···F-C interactions and weak F···F interactions play important roles in the formation of the supramolecular network. Emission properties of I and II are also investigated. The text was submitted by the authors in English.     

The extraction of Zn(II), Cd(II) and Pb(II) from hydrochloric acid media by amberlite LA-2 hydrochloride dissolved in 1,2-dichloroethane

The extraction of HC1 by the secondary amine (B), known as Amberlite LA-2, dissolved in 1,2-dichloroethane and the aggregation of BHC1 have been studied by using a two-phase potentiometric titration technique. The experimental data, treated by a general minimizing program, indicate dimerization: 2 BHClright harpoon over left harpoon(BHCl)(2). The equilibrium constant of this reaction was calculated. The extraction of ZnCl(2), CdCl(2) and PbCl(2) from 0.2,0.5, 1.0 and 2.0M HCl, and 1MNaCl by Amberlite LA-2 hydrochloride (BHCl), dissolved in 1,2-dichloroethane, has been studied. The complexes (BHCl)(2)ZnCl(2), (BHCl)(2)CdCl(2) and (BHCl)(2)PbCl(2) were found to exist, irrespective of the composition of the aqueous phase. The formation constant of the first was calculated.     

Modelling the adsorption of Cd(II), Cu(II), Ni(II), Pb(II), and Zn(II) onto Fithian illite

Illite samples from Fithian, IL were purified and saturated with Na(+) ions. The acid-base surface chemistry of the Na-saturated illite was studied by potentiometric titration experiments with 0.1, 0.01, and 0.001 M NaNO(3) solutions as the background electrolyte. Results showed that the titration curves obtained at different ionic strengths did not intersect in the studied pH range. The adsorption of Cd(II), Cu(II), Ni(II), Pb(II), and Zn(II) onto illite was investigated as a function of pH and ionic strength by batch adsorption experiments. Two distinct mechanisms of metal adsorption were found from the experimental results: nonspecific ion-exchange reactions at lower pH values on the basal surfaces and 'frayed edges' and specific adsorption at higher pH values on the mineral edges. Ionic strength had a greater effect on the ion-exchange reactions. The binding constants for the five heavy metals onto illite were determined using the least-square fitting computer program FITEQL. Linear free energy relationships were found between the surface binding constants and the first hydrolysis constants of the metals.     

Studies on some Ni(II) and Zn(II) diaminomonocarboxylate complexes

pH-metric, calorimetric, NMR and spectro-photometric studies were carried out on the Ni(II) and Zn(II) complexes of 2,3-diaminopropionic acid (dapa), 2,4-diaminobutyric acid (daba), 2,5-diaminopentanoic acid or ornithine (Orn) and 2,6-diaminohexanoic acid or lysine (Lys).It is concluded that the maximum number of coordinated ligands (with the exception of totally deprotonated Orn) is three in the case of Ni(II), but only two in the Zn(II) complexes. The ω-amino groups of dapa, daba and Orn take part in the coordination in the Ni(II) complexes. Hence, with Ni(II) both “diamine type” and “glycine-like” complexes are formed. The tendency to “diamine-like” coordination increases from Orn to dapa, so much so that dapa behaves much rather as a C-substituted 1,2-diamino ethane than a substituted glycine. Only Lys is coordinated to the Ni(II) ion exclusively in a “glycine-like” manner.Zn(II) complexes were studied only to a pH value of 9 (because of precipitation). In this pH region the terminal NH₂ groups take part in the coordination only in the cases of dapa and daba. With Orn and Lys “glycine-like”parent and mixed hydroxo complexes are formed.