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1.
Abstract

The protonation constants of tetraethylenepentaamineheptaacetic acid, TPHA, were determined by potentiometric titration in aqueous solution at an ionic strength of 0.10 M KNO3 and at 25°C. The formation constants of various metal-TPHA complexes were also obtained by titrating mixtures of metal to ligand in molar ratios of 1 :1 and 2:1. Calculations were performed with the computer program BEST. Individual stability constants are reported for Co(II). Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) with TPHA as well as their related pro-tonated species. The stabilities of the 1:1 complexes parallel to those of similar complexes with DTPA and TTHA. However the 2: 1 complexes have significantly larger log K ML's than their TTHA counterparts. The extra stability of the 2:1 metal-TPHA complexes is explained in terms of ligand denticity and steric effects. Mercury(II)-TPHA complexes exhibited the highest formation constants and the copper-TPHA complexes had slightly higher log K ML's than those for Co(II), Ni(II), Zn(II), Cd(II) and Pb(II).  相似文献   

2.
《Analytical letters》2012,45(8):575-584
Abstract

The complexations of a new ligand, o-(2-thiazolylazo)-4-ethylphenol(TAEP) with Ca(II), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hq(II) and Pb(II) have been studied by potentiometric titrations, at 25.0 ± 0.2°C and an ionic strength of 0.1 in 30% v/v dioxane-water mixture. The dissociation constant and spectral data of TAEP and formation constants of the complexes containing various molar ratios of metal ion to ligand, are reported. It is observed that Ca(II) forms only an ML complex in any molar ratios, whereas other metal ions react in two steps forming ML and ML2 complexes in a 1:3 molar ratio. In the case of 1:1 and 1:2 molar ratios, Mn(II), Co(II), Cd(II) and Hg(II) seemed to form bi- or poly-nuclear complexes because of slightly different formation curves from those of 1:3 molar ratio. The sequence of the first successive formation constant is Cu > Hg > Ni > Pb > Co > Zn > Cd > Mn > Ca, showing Mellor-Maley's order. Further correlation is shown between the formation constants and the second ionization potentials of the metals.  相似文献   

3.
《Polyhedron》1987,6(7):1517-1521
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.  相似文献   

4.
A study of the complexes originated by U(VI), Cu(II), Pb(II), Ni(II), Co(II), Zn(II), Cd(II), Mn(II), Ca(II), Mg(II), Ba(II), and Sr(II), and SPADNS (trisodium salt of 2-(p-sulfophenylazo)-1, 8-dihydroxynaphthalene-3,6-disulfonic acid) has been made by means of spectrophotometric and potentiometric methods. The dissociation constants of the ligand and the formation constants of the metal ion-SPADNS complexes have been determined at 25 ± 0.1 °C and ionic strength 0.1 (NaClO4).  相似文献   

5.
The dissociation constants for o-carboxyphenylhydrazoethylacetoacetate (o-CPHEA) ligand, as well as the stability constants for the divalent metal complexes of Cu, (II), Ni (II), Co (II), Zn (II)and Cd (II) ions, have been calculated pH-meterically in different solvents. The dissociation constans pK1=4.10 and pK2=10.55 of the insoluble organic ligand are calculated in aqueous medium. The effect of solvents, the relation between stabilities and both electronegativities and ionization potential are studied.  相似文献   

6.
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)2nH2o (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.  相似文献   

7.
Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 2,5-dichlorobenzoates were prepared and their compositions and solubilities in water at 295 K were determined. The IR spectra and X-ray diffractograms of the obtained complexes were recorded. The complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) were obtained as solids with a 1:2 molar ratio of metal to organic ligand and different degrees of hydration. When heated at a heating rate of 10 K min-1, the hydrated complexes lose some (Co, Zn) or all (Ni, Cu, Cd) of the crystallization water molecules and then decompose to oxide MO (Co, Ni) or gaseous products (Cu, Zn, Cd). When heated at a heating rate of 5 K min-1, the complexes of Ni(II) and Cu(II) lose some (Ni) or all (Cu) of the crystallization water molecules and then decompose directly to MO. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
Abstract

Potentiometric and polarographic studies of metal ion coordination with 9-hydroxypyrido[1,2-α]pyrimidin-4-one (HPP) with Ni(II), Zn(II), Co(II) and Cd(II) ions have been carried out. For comparison, stability constants with 8-hydroxy-imidazo[1,2-α]pyridine (HIP) were also measured. Due to the low solubility of the latter ligand complexes, measurements were made also in dioxan/water solutions. In the case of both ligands the coordination mode is the same. The oxine-like binding via {N, O?} donor set leads to formation of stable ML and ML2 complexes. Stability constants clearly indicate that both ligands are very effective and the HPP, having a more favourable position of the electron pair on nitrogen, forms stronger complexes with smaller metal ions i.e., Ni(II), Zn(II) and Co(II). Cd(II) is better fitted to the HIP donor set.  相似文献   

9.
A new vic-dioxime 1,4,7-oxadithiononane-5,6-dionedioxime (H2L) was prepared from reaction of 2,2-oxydiethanthiol with dichloroglyoxime. Mononuclear complexes of H2L with Ni(II), Co(II), Cu(II), Zn(II), and Cd(II) were also prepared and their structures were determined by means of 1H?NMR, 13C?NMR, IR, and mass spectroscopy. Ni(II), Co(II), and Cu(II) form square planar complexes of 1?:?2 molar ratio of metal to ligand through N,N-chelation, while Zn(II) and Cd(II) form 1?:?1 tetrahedral complexes with a N,O-chelation.  相似文献   

10.
Interactions between pyridine‐2,5‐dicarboxylic acid and Zn(II), Ni(II), Pb(II), Cd(II), and Cu(II) were characterized in aqueous solutions (20°C; I = 0.4 (KNO3)) by means of d.c.‐polarography, spectrophotometry, and 1H NMR spectroscopy. Polarography was used to determine the concentration of free metal ions in the presence of 10‐fold excess ligand in weakly alkaline solutions, and to determine stability constants for the Zn(II), Cd(II), and Cu(II) complexes with pyridine‐2,5‐dicarboxylic acid. 1H NMR spectroscopy was used to further characterize complex formation. © 2005 Wiley Periodicals, Inc. 16:285–291, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20123  相似文献   

11.
《Polyhedron》1988,7(5):393-398
The organometallic ligand derived from ferrocene(H2L), bis(1-methyl-1-benzoylhydrazonoethyl)cyclopentadienyl] iron has been prepared. A series of transition metal complexes: ML [M = Co(II), Ni(II), Zn(II), Cd(II), CU(II) and Mn(II)] and M(H2L)Cl2 [M = Co(II), Ni(II), Cd(II) and Mn(II)] were obtained by reaction of the ligand with metal(II) acetates and chlorides respectively. The data of elemental analyses, IR, UV, NMR, molar conductance, TG and DTA show that the ligand coordinates in the enolic form with M(OAC)2 and in the keto form with MCl2, and that the CN bond in complexes became very strong and much more thermostable than in the ligand due to forming the chelate ring.  相似文献   

12.
The formation constants of salicyl-4-amino-2,3-dimethyl-1-phenyl-3-pyrazoline-5-one (SAAP) complexes with 3d transition metal ions [Cu(II), Ni(II), Co(II), Zn(II) and Mn(II)] have been determined in 60% ethanol-water medium ofμ = 0.1M (NaCl) at 25°C. It is observed that the formation constants for chelates with 3d transition metals follow the order Mn(II) < Co(II) < Ni(II) < Zn(II) < Cu(II). The effects of metal ions, ionic radii, electronegativities and ionization potentials on chelate formation constants are discussed. Complexes of UO2(II) and Pd(II) have been synthesized and characterised by elemental analysis, electrolytic conductance, IR spectra and magnetic measurements. The ligand forms the complexes PdLCl and UO2L2,2H2O, where L is a uninegatively charged tridentate ligand (ONO donor sets).  相似文献   

13.
The formation of complexes of Zn(II), Cd(II), Hg(II), and Pb(II) and N-carboxymethyl-D,L-threonine (H2CMT, H2L) in aqueous solutions has been studied by spectrophotometric and potentiometric methods. The complexation model for each system has been established by the HYPERQUAD program from the potentiometric data. Three different behaviors are found: ML2H, MLH, ML, MLOH, and ML2 complexes are formed by Zn(II) and Cd(II) ions, ML2H, ML, MLOH, and ML2 are formed by Hg(II) ion, and only 1/1 complexes MLH, ML, and MLOH are formed by the Pb(II) ion. The formation constants determined for all these complexes allow simulation of experimental titration curves with good agreement. The speciation of multimetal systems with H2CMT shows that this compound is a good and selective ligand at low pH for the Hg(II) ion.  相似文献   

14.
The formation constants of 1: 1 and 1: 2 complexes between Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Cu(II), Ba(II), Mg(II), Mn(II), Th(IV), and UO2 (II) metal ions and 2-phenyl-3-(2′-hydroxy-5′-methylbenzylidine)-quinazoline-4-(3H)-one [PHBMeQ] were determined potentiometrically at 30 ± 0.1 °C and different ionic strengths (0.025, 0.05, 0.10, 0.15, and 0.20 M NaNO3) in 60: 40 (v/v) alcohol-water solutions. The proton-ligand and metal-ligand formation constants were determined pH-metrically by the Calvin-Bjerrum titration technique. The order of stability constants was found. The negative ΔG° values suggest that the reactions occur spontaneously. Correlations between the log K 1 values and some fundamental central metal ion properties are discussed.  相似文献   

15.
Some mixed ligand complexes containing 2-methylbenzimidazole and thiocyanate ion were synthesized. Free ligands and their metal complexes were characterized using elemental analysis, determination of metal, magnetic susceptibility, molar conductivity, infrared, UV-VIS, and (1H, 13C) NMR spectra, and X-ray structure analysis. The results suggest that the Ag(I) complex has linear geometry, Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have tetrahedral geometry, Pd(II) complex has square planar geometry, VO(IV) square pyramidal geometry, Pb(II) irregular tetrahedral geometry, and that the Cr(III) and Mn(II) complexes have octahedral geometry. The following general formulae were proposed for the prepared complexes: [AgBX], [CrB3X3], (HB)2[MnB2X4] · 2B and [MB2X2], where B = 2-methylbenzimidazole, HB = 2-methylbenzimidazolium, X = thiocyanate ion, and M = VO(IV), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Cd(II), and Pb(II). Molar conductance of a 10−3 M solution in N,N-dimethyl formamide (DMF) indicates that all the complexes are non-electrolytes except the Mn(II) complex which is an electrolyte because the molar conductivity of its solution in DMF is high.  相似文献   

16.
Metal complexes of some divalent metal ions (Co, Ni, Cu, Zn, Hg, and Pd) with isatin-β-thiosemicarbazone (ITS) as the Schiff base have been investigated potentiometrically and spectrophotometrically. The dissociation constants of the ligand and formation constants of the metal complexes, as well as the corresponding thermodynamic functions (ΔG, ΔH and ΔS) have been determined at different temperatures in ethanol—water solution. The full stability constants were also evaluated spectrophotometrically by the Job method. The experimental results indicate that Cu(II), Zn(II), Pd(II), and Hg(II) form one-to-one molecular complexes (ML) with the studied ligand, whereas Co(II) and Ni(II) form both ML and ML2 species.  相似文献   

17.
The syntheses of mixed oxygen-nitrogen donor macrocycles incorporating two or three pendant carboxylic acid groups are described. Potentiometric titrations in water (I = 0.1; KNO3) at 25°C have been used to determine the stability constants for the 1: 1 (metal:ligand) complexes of Co(II). Ni(II), Cu(II), Zn(II), and Cd(II). The constants obtained are compared with the previously determined values for the corresponding complexes of the unsubstituted macrocyclic precursors. The results of these studies indicate that each carboxylate function participates in binding to the central metal. For some metal-ion/ligand systems there is evidence that ring size effects influence the overall stability patterns and that, in such cases, both the ether oxygens as well as the tertiary amines of the macrocyclic rings appear to bind to the metal.  相似文献   

18.
Summary The interaction of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Al(III), and UO2(II) ions with tetracycline (TC) were studied by potentiometricpH titrations. The formation constants of the different binary complexes formed in such systems have been determined at 25±0.1°C and =0.1 moll–1 (NaNO3). PotentiometricpH equilibrium measurements have been made under the same conditions for the interaction of oxytetracycline (OTC) and Cu(II), Cd(II), Pb(II), and UO2(II). The formation of (1:1) binary complexes are inferred from the potentiometricpH tritration curves. The protonation constants ofTC andOTC were also determined under the same conditions and refined (ESAB2M computer program). The transition metal stability constants are consistent with the Irving-Williams series.
Potentiometrische Untersuchungen der Komplexe von Tetracyclin (TC) and Oxytetracyclin (OTC) mit einigen Metall-Ionen
Zusammenfassung Die Wechselwirkungen von Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Al(III) und UO2(II) Ionen mit Tetracyclin (TC) wurden mittels potentiometrischerpH-Titrationen untersucht. Die Komplexbildungskonstanten wurden bei 25±0.1°C und =0.1 mol/1(NaNO3) bestimmt. Unter den gleichen Bedingungen wurden die Komplexierung von Cu(II), Cd(II), Pb(II) und UO2(II) mit Oxytetracyclin (OTC) mittel potentiometrischerpH Gleichgewichtsmessungen untersucht. Aus den potentiometrischenpH-Titrationskurven ergab sich die Bildung von (1:1) binären Komplexen. Die Protonierungskonstanten vonTC undOTC wurden ebenfalls bestimmt und rechnerisch verfeinert (ESAB2M Computer Programm). Die Stabilitätskonstanten für die Übergangsmetalle stimmen mit der Irving-Williams Reihe überein.
  相似文献   

19.
The reactions of complex formation of Cu(II), Co(II), Zn(II), Ni(II), and Cd(II) acetates with 3,3′,4,4′5,5′-hexamethyl-2,2′-dipyrrolylmethene (HL) in DMF were studied by the electronic spectroscopy and calorimetric titration methods at 298.15 K. The main products of the above reactions are [ML2] chelates. In the case of Cu and Ni salts, the process occurs through the spectrally recorded stage of formation of the heteroligand [ML(AcO)] complexes. The reaction with Cd acetate terminates at the stage of the heteroligand complex formation due to the large radius and decreasing electron affinity of the Cd2+ ion. The effect of the metal nature appears in the increasing thermodynamic stability of single-type complexes in the series [ML2]: Ni(II) < Zn(II) < Co(II) < Cu(II) and [ML(AcO)]: Cd(II) < Ni(II) < Cu(II).  相似文献   

20.
The proton dissociation constant of the ligand and the stability of the complexes of Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Cu(II), Ba(II), Mg(II), Mn(II), Th(IV), and UO2(II) ions with 2-phenyl-3-(2′-hydroxy-5′-benzylidine)-quinazoline-4-(3H)-one [PBQ] were determined potentiometrically at 30 ± 0.1°C and ionic strengths of 0.025, 0.05, 0.10, 0.15 and 0.20 M NaNO3 in a 60:40 (v/v) ethanol-water medium. The proton-ligand and metal-ligand stability constants of the complexes were determined pH metrically by the Calvin-Bjerrum titration technique. The order of stability constants obeys the Irving-Rossotti rule. The negative values of ΔG° suggest that the reactions are spontaneous. The article is published in the original.  相似文献   

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