Isomorphous replacement of M(II) ions in M(II)-Gd(III) dimers (M(II) = Cu(II), Mn(II), Ni(II), Co(II), Zn(II)): magnetic studies of the products

Complexes [M(II)Gd(III){pyCO(OEt)pyC(OH)(OEt)py}?](ClO?)?·EtOH [M(II) = Cu(II) (1), Mn(II) (2), Ni(II) (3), Co(II) (4) and Zn(II) (5)] crystallize in the monoclinic Cc space group and contain one hexacoordinate M(II) ion and one enneacoordinate Gd(III) ion, bridged by three {pyCO(OEt)pyC(OH)(OEt)py}? ligands. Magnetic susceptibility measurements indicate a ferromagnetic interaction for 1 and antiferromagnetic interactions for 2-4. Using the ? = -J?(Gd(III))?(M(II)) spin Hamiltonian formalism, fits to the magnetic susceptibility data yielded J values of +0.32 cm?1 for 1, -1.7 cm?1 for 2, and -0.22 cm?1 for 3. In complex 4, the orbital contributions of Co(II) precluded the determination of the magnetic coupling. The complex follows the Curie-Weiss law with θ = -2.07 K (-1.44 cm?1).     

Constructing Phenoxo-Bridged Heterobimetallic [Zn(II)2M(II)] (M = Sr and Ba) Salamo-Based Complexes

Russian Journal of General Chemistry - Two new phenoxo-bridged heterobimetallic [Zn(II)2M(II)] (M = Sr and Ba) salamo-based complexes, [{Zn(L)(μ2-OAc)}2Sr]·0.33CH3OH·H2O (1) and...     

Single crystal circular and linear dichroism spectra and absolute configuration of M(en)3(NO3)2 (M = Zn(II), Cu(II), Ni(II), Co(II), Mn(II) and Ru(II)

The isomorphous single crystals of M(ethylenediamine)₃(NO₃)₂, where M is Zn(II), Ni(II) and Co(II), exhibit macroscopic optical activity as predicted by their acentric space group. Axial circular dichroism measurements on these pure crystals show conclusively that spontaneous resolution has occurred. The axial circular dichroism and orthoaxial linear dichroism spectra of these pure crystals, and of Cu(II), Ni(II), Co(II), Mn(II) and Ru(II) doped into the Zn(en)₃(NO₃)₂ crystal have been measured at ambient and cryogenic temperatures in the range from 7 to 35 kK. The first NO₃^? transition at 32.5 kK is assigned as ¹A ← ¹A based on its linear polarization and sign of rotational strength. The d-d transitions are assigned in the context of D₃ symmetry and reveal a small negative crystal field parameter k, consistent with theoretical prediction. A positive R for all d-d transitions is found to be associated with the Λ configuration for all of the complex ions, by correlation with the crystal and solution circular dichroism of Ru(en)₃²⁺.     

Clathrate formation in the [M(4-MePy)2 (NCS)2]-4-MePy systems,where M=Co(II), Ni(II), Zn(II), Cd(II); 4-MePy=4-methylpyridine

A number of complexes [M(4-MePy)_n (NCS)₂], where M=Co(II), Ni(II), Zn(II), Cd(II); n=2 or 4 have been synthesized and phase diagrams [M(4-MePy)₂(NCS)₂]-4-MePy have been studied. The forming compounds have been obtained and described with the help of IR-spectroscopy and thermal analysis. The structure of a molecular type with variable section channels, filled by two types guest-molecules (by a water molecule in the narrow part of the channel and by two 4-methylpyridine molecules in the broad part of the channel, with a total ratio guest: host being 1:1) for [Cd(4-MePy)₄ (NCS)₂]·0.67(4-MePy)·0.33H₂O has been defined by X-ray method. This clathrate is isostructural (X-ray powder diffractogram) to the anhydrous compound [Cd(4-MePy)₄ (NCS)₂]·0.67(4-MePy).     

Magnetic Properties of M3[Fe(Cn)6]2Xh2O (M = Co (II), Ni(II), Cu(II), Zn(II))

Compounds of the type M₃[Fe(CN)₆]₂XH₂O (M = Co(II), Ni(II), Cu(II), and Zn(II)) were prepared and magnetic properties of their powders were investigated by means of EPR spectra, Mössbauer effect and magnetic susceptibility measurements. The temperature dependence of the magnetization for the complexes Co₃[Fe(CN)₅]₂- 10H₂O, Ni₃[Fe(CN)₆]₂-10H₂O and Cu₃[Fe(CN)₆]₂-4H₂O revealed that below the critical temperatures 15, 22 and 20 K respectively, these complexes have zero-field magnetization. The magnetic hysteresis at 10 K for Co(II), Ni(II) and Cu(II) complexes was observed. Mössbauer spectra at 4.2 K for the compounds are discussed.     

Structure of M(OOPh)<Subscript>2</Subscript>[O(H)Me]<Subscript>4</Subscript> (M = Zn(II), Co(II), and Ni(II)) adducts

The structures of adducts M(OOPh)₂[O(H)Me]₄ (M = Zn(II), Co(II), and Ni(II)), synthesized by the reactions between corresponding aqueous metal acetates and benzoic acid under boiling in methanol were studied by X-ray diffraction.     

Hydrothermal syntheses and single crystal structural characterization of M(H2O)6(OPTA)2 [M = Co(II), Ni(II), Zn(II); OPTA = 1-oxopyridinium-2-thioacetato]

A new class of compounds of the family M(H₂O)₆(OPTA)₂ (where M = Co(II), Ni(II), and Zn(II); OPTA = 1-oxopyridinium-2-thioacetato) was prepared from the appropriate metal acetates, 1-oxo-pyridinium-2-thioacetic acid (OPTAH), and potassium hydroxide in hydrothermal media and structurally characterized. The structure is constructed from M(H₂O)₆ ²⁺ and two anions of OPTAH (C₇H₆NO₃S) linked through hydrogen bonding into an extended network.     

Solid-state coordination chemistry: influences of (M(terpyridyl))(M = Fe(III), Cu(II), Ni(II)) subunits on molybdenum oxide structures

The hydrothermal reactions of Na2MoO4 x 2H2O and 2,2':6',2"-terpyridine with appropriate salts of Fe(II), Cu(II), and Zn(II) yield a variety of mixed metal oxide phases. The Cu(II) system affords the molecular cluster [Cu(terpy)MoO4].3H2O (MOXI-40 x 3H2O), as well as a one-dimensional material [Cu(terpy)Mo2O7](MOXI-41) which is constructed from (Mo4O14)4- clusters linked through (Cu(terpy))2+ units. In constrast, the Zn(II) phase of stoichiometry identical to that of MOXI-41, [Zn(terpy)Mo2O7](MOXI-42), exhibits a one-dimensional structure characterized by a (Mo2O7)n2n- chain decorated with peripheral (Zn(terpy))2+ subunits. The iron species [(Fe(terpy))2Mo4O12](MOXI-43) is also one-dimensional but exhibits [(Fe(terpy))2(MoO4)2]2+ rings linked through (MoO4)2- tetrahedra. A persistent structural motif which appears in MOXI-40, MOXI-41, and MOXI-43 is the [(M(terpy))2(MoO4)2]n cluster with a cyclic )(M2Mo2O4) core. In general, the secondary metal sites M(II, III) are effective bridging groups between molybdate subunits of varying degrees of aggregation. Furthermore, the ligands passivate the bimetallic oxide from spatial extension in two or three dimensions and provide a routine entree into low-dimensional structural types of the molybdenum oxide family of materials.     

Synthesis and structural studies of 2-acetylthiophene-2-thenoylhydrazone complexes of oxovanadium(IV), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II)

Complexes with chemical compositions VO(Hatth)₂SO₄, VO(Hatth)₂SO₄·py, [M(Hatth)₂Cl·H₂O]Cl [M = Mn(II), Co(II) and Ni(II)], [Cu(Hatth)₂Cl]₂Cl₂, [Cu(Hatth)₂· Cl·py]Cl, [Cd(Hatth)₂Cl]Cl, M(Hatth)₂Cl₂ [M = Zn(II) and Hg(II)], VO(atth)₂, VO(atth)₂py, M(atth)₂(py)₂ [M = Mn(II) and Cu(II)], M(atth)₂(H₂O)₂ [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)], Hatth = 2-acetylthiophene-2-thenoylhydrazone, and atth, its deprotonated form, have been prepared and characterized by analytical data, molar conductance, magnetic susceptibility, electronic and photoacoustic, ESR, IR and NMR spectral studies. X-ray diffraction study has been used to determine the shape and the dimensions of the unit lattice of copper(II) complexes.     

Synthesis and magnetic properties of heterometal cyclic tetranuclear complexes [Cu(II)LM(II)(hfac)]2 (M(II) = Zn,Cu, Ni,Co, Fe,Mn; H3L = 1-(2-hydroxybenzamido)-2-((2-hydroxy-3-methoxybenzylidene)amino)ethane; Hhfac = hexafluoroacetylacetone)

A series of heterometal cyclic tetranuclear complexes [Cu(II)LM(II)(hfac)](2) (M(II) = Zn (1), Cu (2), Ni (3), Co (4), Fe(5), and Mn (6)) have been synthesized by the assembly reaction of K[CuL] and [M(II)(hfac)(2)(H(2)O)(2)] with a 1:1 mole ratio in methanol, where H(3)L = 1-(2-hydroxybenzamido)-2-((2-hydroxy-3-methoxybenzylidene)amino)ethane and Hhfac = hexafluoroacetylacetone. The crystal structures of 2, 4, and [Cu(II)LMn(II)(acac)](2) (6a) (Hacac = acetylacetone) were determined by single-crystal X-ray analyses. Each complex has a cyclic tetranuclear Cu(II)(2)M(II)(2) structure, in which the Cu(II) complex functions as a "bridging ligand complex", and the Cu(II) and M(II) ions are alternately arrayed. One side of the planar Cu(II) complex coordinates to one M(II) ion at the two phenoxo and the methoxy oxygen atoms, and the opposite side of the Cu(II) complex coordinates to another M(II) ion at the amido oxygen atom. The temperature-dependent magnetic susceptibilities revealed spin states of S(M) = 0, 1/2, 1, 3/2, 2, and 5/2 for the Zn(II), Cu(II), Ni(II), Co(II), Fe(II), and Mn(II) ions, respectively. Satisfactory fittings to the observed magnetic susceptibility data were obtained by assuming a rectangular arrangement with two different g-factors for the Cu(II) and M(II) ions, two different isotropic magnetic exchange interactions, J(1) and J(2), between the Cu(II) and M(II) ions, and a zero-field splitting term for the M(II) ion. In all cases, the antiferromagnetic coupling constants were found for both exchange interactions suggesting nonzero spin ground states with S(T) = 2/S(M) - S(Cu)/, which were confirmed by the analysis of the field-dependent magnetization measurements.     

Hydrothermal synthesis and characterization of 2D M(II)-Quinate (M = Co,Zn) metal-organic lattice assemblies: solid-state solution structure correlation in M(II)-hydroxycarboxylate systems

Co(II) and Zn(II) ions exhibit variable reactivity toward O-containing ligands in aqueous media, affording isolable materials with distinct solid-state lattice properties. d-(-)-quinic acid is a cellular α-hydroxycarboxylate metal ion binder, which reacts with Co(II) and Zn(II) under pH-specific hydrothermal conditions, leading to the isolation of two new species [Co(2)(C(7)H(11)O(6))(4)](n)·nH(2)O (1) and [Zn(3)(C(7)H(11)O(6))(6)](n)·nH(2)O (2). Compound 1 was characterized by elemental analysis, spectroscopic techniques (FT-IR, UV-visible, EPR), magnetic studies, and X-ray crystallography. Compound 2 was characterized by elemental analysis, spectroscopic techniques (FT-IR, ESI-MS), and X-ray crystallography. The 2D molecular lattices in 1 and 2 reveal the presence of octahedral M(II) units bound exclusively to quinate in a distinct fashion, thereby projecting a unique chemical reactivity in each investigated system. The magnetic susceptibility and solid-state/frozen solution EPR data on 1 support the presence of a high-spin octahedral Co(II) in an oxygen environment, having a ground state with an effective spin of S = 1/2. Concurrent aqueous speciation studies on the binary Zn(II)-quinate system unravel the nature and properties of species arising from Zn(II)-quinate interactions as a function of pH and molar ratio. The physicochemical profiles of 1 and 2, in the solid state and in solution, earmark the importance of (a) select synthetic hydrothermal reactivity conditions, affording new well-defined lattice dimensionality and nuclearity M(II)-quinate materials, (b) structural speciation approaches delineating solid state-aqueous solution correlations in the binary M(II)-quinate systems, and (c) pH-specific chemical reactivity in binary M(II)-quinate systems reflecting structurally unique associations of simple aqueous complexes into distinctly assembled 2D crystalline lattices.     

Zinc(II), Cadmium(II), and Mercury(II) Complexes of 2-Methyl-benzoselenazole

The following zinc(II), cadmium(II) and mercury(II) complexes of 2-methyl-benzoselenazole (L) have been prepared and studied by conductometric and i.r. methods: MLX₂ (M ? Cd, Hg, X ? Cl, Br, I), ML_1.5X₂ (M ? Zn, X ? ClO₄(4 H₂O); M ? Hg, X ? NO₃, ClO₄), ML₂X₂ (M ? Zn, X ? Cl, Br, I, NO₃; M ? Cd, X ? NO₃, ClO₄). The ligand is N-bonded. All the anions are coordinated.     

Synthesis,structure and properties of three one-dimensional coordination polymers {[M(II)L(NCS)2](DMF)2} n (M(II)=cadmium(II), zinc(II), manganese(II); L=1,4-bis[2-(2-pyridyl)benzimidazolato]butane)

A tetradentate N-donor ligand 1,4-bis[2-(2-pyridyl)benzimidazolato]butane (L) was prepared for construction of a coordination framework. Three one-dimensional coordination polymers {[M(II)L(NCS)₂](DMF)₂} _n (M(II) = cadmium(II), 1, zinc(II), 2, manganese(II), 3) were obtained by reaction of metal ions and L in the presence of KSCN in DMF/water. The complexes are isostructural and consist of 1D zigzag [M(II)L(NCS)₂] _n chains and DMF molecules. Within the chains, the metal atoms are each octahedrally coordinated by four N atoms of L and two N atoms of the SCN^? anions. Complexes 1 and 2 in the solid state at room temperature exhibit intense photoluminescence at 453 and 433 nm, respectively.     

Spectral,thermal and magnetic investigations of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates

Conditions for the preparation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 4-methylphthalates were investigated and their composition, solubility in water at 295 K and magnetic moments were determined. IR spectra and powder diffraction patterns of the complexes prepared with molar ratio of metal to organic ligand of 1.0:1.0 and general formula: M [ CH₃C₆H₃(CO₂)₂]·nH₂o (n=1-3) were recorded and their decomposition in air were studied. During heating the hydrated complexes are dehydrated in one (Mn, Co, Ni, Zn, Cd) or two steps (Cu) and next the anhydrous complexes decompose to oxides directly (Cu, Zn), with intermediate formation of carbonates (Mn, Cd), oxocarbonates (Ni) or carbonate and free metal (Co). The carboxylate groups in the complexes studied are mono- and bidentate (Co, Ni), bidentate chelating and bridging (Zn) or bidentate chelating (Mn, Cu, Cd). The magnetic moments for paramagnetic complexes of Mn(II), Co(II), Ni(II) and Cu(II) attain values 5.92, 5.05, 3.36 and 1.96 M.B., respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural, spectroscopic and thermal characterization of 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester and its Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO(2)(II) complexes

Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO(2)(II) complexes with the ligand 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester (HL(2)) have been prepared and characterized by elemental analyses, molar conductance, magnetic moment, thermal analysis and spectral data. 1:1 M:HL(2) complexes, with the general formula [M(HL(2))X(2)].nH(2)O (where M = Co(II) (X = Cl, n = 0), Ni(II) (X = Cl, n = 3), Cu(II) (grey colour, X = AcO, n = 1), Cu(II) (yellow colour, X = Cl, n = 0) and Zn(II) (X = Br, n = 0). In addition, the Fe(III) and UO(2)(II) complexes of the type 1:2 M:HL(2) and with the formulae [Fe(L(2))(2)]Cl and [UO(2)(HL(2))(2)](NO(3))(2) are prepared. From the IR data, it is seen that HL(2) ligand behaves as a terdentate ligand coordinated to the metal ions via the pyridyl N, carboxylate O and protonated NH group; except the Fe(III) complex, it coordinates via the deprotonated NH group. This is supported by the molar conductance data, which show that all the complexes are non-electrolytes, while the Fe(III) and UO(2)(II) complexes are 1:1 electrolytes. IR and H1-NMR spectral studies suggest a similar behaviour of the Zn(II) complex in solid and solution states. From the solid reflectance spectral data and magnetic moment measurements, the complexes have a trigonal bipyramidal (Co(II), Ni(II), Cu(II) and Zn(II) complexes) and octahedral (Fe(III), UO(2)(II) complexes) geometrical structures. The thermal behaviour of the complexes is studied and the different dynamic parameters are calculated applying Coats-Redfern equation.     

Application of chelate forming resin Amberlite XAD-2-o-vanillinthiosemicarbazone to the separation and preconcentration of copper(II), zinc(II) and lead(II)

A very stable chelating resin matrix was synthesized by covalently linking o-vanillinthiosemicarbazone (oVTSC) with the benzene ring of the polystyrene-divinylbenzene resin Amberlite XAD-2 through a -NN- group. The resin was used successfully for the separation and preconcentration of copper(II), zinc(II) and lead(II) prior to their determination by atomic absorption spectrophotometry. The total sorption capacity of the resin was 850, 1500 and 2000 mug g(-1) of the resin for Cu(II), Zn(II) and Pb(II), respectively. For the quantitative sorption and recovery of Cu(II), Zn(II) and Pb(II), the optimum pH and eluants were pH 2.5-4.0 and 4 M HCl or 2 M HNO(3) for Cu(II), pH 5.5-6.5 and 1.0-2.0 M HCl for Zn(II) and pH 6.0-7.5 and 3 M HCl or 1 M HNO(3) for Pb(II). Both, the uptake and stripping of these metal ions were fairly rapid, indicating a better accessibility of the chelating sites. The t (1 2 ) values for Cu(II), Zn(II) and Pb(II) were also determined. Limit of tolerance of some electrolytes like NaCl, NaF, NaNO(3), Na(2)SO(4) and Na(3)PO(4) have been reported. The preconcentration factor for Cu(II), Zn(II) and Pb(II) was 90, 140 and 100 respectively. The method was applied for the determination of Cu(II), Zn(II) and Pb(II) in the water samples collected from Sabarmati river, Ahmedabad, India.     

Tetrakis(thiadiazole)porphyrazines. 8. Singlet oxygen production, fluorescence response and liposomal incorporation of tetrakis(thiadiazole)porphyrazine macrocycles [TTDPzM] (M = Mg(II)(H2O), Zn(II), Al(III)Cl, Ga(III)Cl, Cd(II), Cu(II), 2H(I))

The photoactivity for the generation of singlet oxygen, (1)O(2), the key cytotoxic agent in the anticancer treatment known as photodynamic therapy (PDT), and the fluorescence response of the highly electron-deficient tetrakis(thiadiazole)porphyrazines of formula [TTDPzM] (M = Mg(II)(H(2)O), Zn(II), Al(III)Cl, Ga(III)Cl, Cd(II), Cu(II), 2H(I)) were examined (c ? 10(-5) M) in dimethylformamide (DMF) and/or in DMF preacidified with HCl (DMF/HCl; [HCl] = 1-4 × 10(-4) M). The singlet oxygen quantum yield (Φ(Δ)) of all the compounds was determined by using a widely employed procedure based on the selective oxidation of the 1,3-diphenylisobenzofuran (DPBF), modified in part as reported. The list of the Φ(Δ) values indicates excellent photosensitizing properties for the series of compounds carrying "closed shell" metal ions, with values measured in DMF/HCl respectful of the "heavy atom effect" for the first four lighter centers, increasing in the order Mg(II) < Al(III) < Zn(II) < Ga(III). Data of Φ(Δ) concerning the unmetalated species [TTDPzH(2)], present in solution in the form of the corresponding anion [TTDPz](2-), and the Cd(II) and Cu(II) complexes are also presented and discussed. Extensive discussion is also developed on the fluorescence quantum yield values Φ(F), with data on the Mg(II) and Al(III) compounds in DMF/HCl (0.44 and 0.53, respectively) indicative of promising perspectives for applications in fluorescence imaging techniques. The Φ(F) data of the studied porphyrazine series, Φ(F)(Pz), correlate linearly with those of the homologous phthalocyaninato complexes, Φ(F)(Pc), suggesting a closely similar behaviour between the two classes of compounds. The incorporation of [TTDPzZn] into liposomes was successfully achieved following the detergent depletion method (DDM) from a mixed micellar solution by means of gel-filtration. Retention of [TTDPzZn] (~40%) in its photoactive monomeric form into liposomes is proved by absorption and fluorescence spectra, this proposing the Zn(II) complex as a promising candidate for use in PDT.     

The binding of trace amounts of lead(II), copper(II), cadmium(II), zinc(II) and calcium(II) to soil organic matter

The binding by peat of Ca(II), Cd(II), Zn(II), Cu(II) and Pb(II) present at trace-level concentrations in 0.0010, 0.010 and 0.10M sodium chloride, has been studied as a function of the degree of neutralization of the soil organic acid. The theoretically-based method used to express the complexation equilibria requires values for the concentrations of the several mobile counter-ions in the peat phase [M (II), H (+) and N a(+)] and permits estimation of the nature of the complexed species formed in the peat as well as of reasonable values for the formation constants of the species formed. The values of the formation constants thus obtained are independent of the ionic strength of the equilibrating solution, as they should be. This result was unattainable with the earlier methods of computation used for studying these equilibria. The species formed are Ca(II)A(+).HA and M(II)A(+), where M(II) represents Cd(II), Zn(II), Cu(II) and Pb(II).     

Bonding analyses, formation energies, and vibrational properties of M-R2dtc complexes (M=Ag(I), Ni(II), Cu(II), or Zn(II))

Detailed theoretical studies based on density functional theory (DFT)/B3LYP calculations of dimethyl- and diethyldithiocarbamate complexes of Ni(II), Cu(II), Zn(II), and Ag(I) are performed to characterize the metal-ligand bonding type as well as the metal-ligand bonding strength depending on the metal and the dialkyl substituent. The metal-ligand interactions in the studied complexes are investigated by means of charge decomposition analysis, energy partitioning analysis (EPA), and natural bond orbital analysis. According to the EPA calculations, the electrostatic attraction is the dominant contribution to the M-S2(R2dtc) (dtc=dithiocarbamate) bonding. The electrostatic and the orbital energies follow the order of the total binding energy, and hence both contributions are responsible for the binding energy order of M(R2dtc)2 complexes. The stability of the M(R2dtc)2 complexes is estimated by means of calculated formation reaction energies in the gas phase and solution, and it decreases in the order Ni(R2dtc)2>Cu(R2dtc)2>Zn(R2dtc)2. Larger formation reaction energies are found for M(Et2dtc)2 than for M(Me2dtc)2 complexes. The calculations predict stabilization of M(II)(R2dtc)2 complexes going from the gas phase to a polar solvent and destabilization of the bidentate AgR2dtc complex in a polar solvent. Gas-phase frequency calculations of all possible bonding types, symmetrical, asymmetrical, and uni- and bidentate, predict one band due to the nu(CS) IR absorption, and therefore the number of the bands in the 1060-920 cm(-1) region could not be used to discern the metal-ligand bonding type. Periodic DFT frequency calculations for Cu(Et2dtc)2 reveal that the splitting observed in the solid-state spectra of the complexes arises from the nonplanar MS4 fragment and intermolecular contacts but not from asymmetrical bonding. The calculations suggest that the important vibrational characteristic that can be used to discern uni- and bidentate bonding is the Raman activity of the nu(CS) band: It is very high for the unidentate dtc bonding (nu(C=S)) and low for the bidentate bonding (nuas(CS)).     

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.