Ternary complexes in solution: Complex formation between copper(II), zinc(II), cadmium(II) and ligands of biological importance

The stability constants of ternary complexes of theMAL type have been determined for Cu(II), Zn(II) and Cd(II). The ligands chosen for this study belong to the biologically important ones viz. Bipyridyl (A) and Nitrilotriacetic acid (L). LogK _MAL values for Cu(II), Zn(II) and Cd(II) are 11.42, 10.67 and 9.72, respectively, at temp.=25°C and =0.1M (KNO₃); the order is discussed.

---

Ternäre Komplexe in Lösung: Die Komplexibildung zwischen Kupfer(II), Zink(II) und Kadmium(II) mit Liganden von biologischem Interesse

Zusammenfassung Die Stabilitätskonstanten für Cu(II)-, Zn(II)- und Cd(II)-Komplexe vom TypMAL wurden bestimmt. Die biologisch relevanten Liganden, die für diese Untersuchung ausgewählt wurden, waren Bipyridyl (A) und Nitrilotriessigsäure (L). Bei einer Temperatur von 25°C und =0,1M (KNO₃) sind die entsprechenden logK _MAL -Werte für Cu(II), Zn(II) und Cd(II) 11,42, 10,67 und 9,72; diese Reihenfolge wird ebenfalls diskutiert.

     

Complex formation studies on copper(II) and zinc(II) with asparagine and aspartic acid in aqueous solution

The complex equilibria of the systems copper—aspartic acid, zinc—aspartic acid, copper—asparagine, and zinc—asparagine have been studied by computer analysis of potentiometric data.     

Heat effects of complex formation between maleic acid and zinc(II) and nickel(II) ions

The heat effects of formation of zinc(II) and nickel(II) complexes with maleic acid were determined by the direct calorimetric method at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solution were calculated.     

Complex formation of copper(II) and nickel(II) with N-arylthiopicolinamides

The reactions of N-arylthiopicolinamides (HL) with copper(II) and nickel(II) ions in organic and aqueous-organic solutions were studied. On addition of HCl, the transformation of ML₂ complexes into M(HL)Cl₂ occurs, while the reverse reaction takes place under the action of amphoteric protic solvents. The structures of the isolated complexes were established by IR and UV spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1546–1550, September, 1993.     

Thermodynamics and vapor formation features of zinc(II) and tin(II) pivalates

Vapor formation of tin(II) and zinc(II) pivalates were studied using the Knudsen effusion method and mass spectrometry analysis of the gas phase. Sublimation of the tin complex is shown to be accompanied by polymerization of the condensed phase, changing its thermodynamic parameters. The vapor formation of zinc pivalate in the presence of trace amounts of water is accompanied by partial hydrolysis of the condensed phase and sublimation of the sample in the form of Zn₄O(piv)₆ and Zn₂piv₄. The absolute partial pressures and heats of sublimation of the components of the gas phase above tin and zinc complexes are calculated.     

Stereoselective formation of cobalt(II), nickel(II) and zinc(II) chelates of histidine

Formation of the 2: 1 histidine complexes of cobalt(II), nickel(II), and zinc(II) is stereoselective, the mixed D, L-complexes being preferred over the unmixed L, L-complexes, in aqueous solutions. Analysis of titration data indicates that the racemic cobalt(II), nickel(II) and zinc(II) complexes are favored by 12, 22, and 13 per cent respectively, over what is expected statistically. The stereoselectivity observed for the zinc(II) complexes suggests that they possess octahedral characteristics in aqueous solution. No stereoselectivity is observed in the cadmium(II) and copper (II) bis complexes of histidine, nor in the nickel(II) and copper(II) bis complexes of 2,3-diaminopropionic acid. Stereoselectivity appears to be dependent upon the presence of a bulky side chain in a tridentate ligand chelated to a small metal ion.     

Complex compounds of 1,5-disubstituted 2,4-dithiobiurets with zinc(II) and cadmium(II) chloride

Anhydrous ZnCl₂ and CdCl₂ react with 1,5-disubstituted 2,4-dithiobiurets to give complexes of general formula [ML₂]Cl₂. The complexes have been characterized on the basis of conductance, magnetic and i.r. spectral studies. Co-ordination through sulphur atom and tetrahedral configuration have been proposed for these complexes.     

Heats of formation of iodo-complexes of zinc(II), cadmium(II) and mercury(II) in aqueous solutions

Heats of formation of MeI⁺, MeI₂, MeI₃^? and MeI₄^2? where Me²⁺, Cd²⁺ or Hg²⁺ were determined in acidic solutions by flow microcalorimetry. Some gaps in the literature data were filled. In particular, ΔH₃ for the mercury(II) complex was determined and the ΔH₁, ΔH₂ + ΔH₃, ΔH₄ for zinc(II) complexes were measured in sodium free solutions to avoid ionic couple formation. For cadmium(II) complexes, existing data were confirmed. Thermodynamic functions are discussed in term of hard/soft interactions.     

Cooperative formation of trinuclear zinc(II) complexes via complexation of a tetradentate oxime chelate ligand, salamo, and zinc(II) acetate

Novel trinuclear zinc(II) complexes [Zn(3)L(2)(OAc)(2)] (L = salamo, 3-MeOsalamo) were synthesized, and their structures were determined by X-ray crystallography. Ligation of methoxy groups in the salamo ligand causes a significantly different coordination mode of the central zinc atom in the trinuclear system. The complexes between the salamo ligands and zinc(II) in methanol formed exclusively and very cooperatively. In contrast to other imine ligands, the mononuclear [ZnL] and other complexes are not observed at all.     

Complex formation of copper(II) with triethylenetetraminehexaacetic acid

The interaction between copper (II) and triethylenetetraminehexaacetic acid (TTHA) was investigated by polarographic, spectrophotometric and potentiometric methods. The existence of chelates with the formulae CuH-TTHA, Cu-TTHA and Cu₂-TTHA was shown. The polarographic behaviour and absorption curves of the chelates are described and the equilibrium constants defining the formation of the various species, are reported.     

Complex formation of mercury(II) chloride with dipeptides

Russian Journal of General Chemistry - Mixed-ligand complex formation in the HgCl–L systems (L= GlyGly, AlaAla) has been studied by pH potentiometry, calorimetry, and 1Н and 13С...     

Complex formation equilibria between mercury(II) complexes of pencillamine and glutathione and transition metal ions

Summary The interaction between Hg^II complexes of the thiols pencillamine and glutathione and some transition metal ions has been investigated potentiometrically. Mixedmetal complexes of the forms Hg(ps)₂M and Hg(gs)₂M (where M=Co or Ni), were detected. The complexes formed between glutathione disulphide with bivalent metal ions Zn^II, Ni^II, Co^II and Cd^II have also been studied. Zn^II and Ni^II form the complexes M(gssg)H and M(gssg), while Co^II and Cd^II form only the fully deprotonated complex M(gssg). The formation constants of the complexes were determined at 25°C and I=0.1 M (NaNO₃). The concentration distribution of various complex species as a function of pH was evaluated.     

Complex formation equilibria of some beta-amino-alcohols with lead(II) and cadmium(II) in aqueous solution

A study of complex formation equilibria of some beta-amino-alcohols with lead(II) and cadmium(II) ions at 25 degrees C and in 0.5 M KNO(3) is reported. The amino-alcohols considered are 2-amino-1-propanol, 2-amino-1-butanol, 2-amino-1-pentanol and 2-amino-1,3-propanediol. sec-Buthylamine and 2-amino-1-methoxy-propane have been also considered for comparison. The results are discussed in terms of ligand structure, paying attention to the number of hydroxyl groups and to the length of the alkyl residual. A weak contribution of the alcoholic oxygen in the coordination of cadmium(II) and the presence of a mixed hydroxyl species in lead(II) containing systems are hypothesized.     

Deprotonation of zinc(II)-water and zinc(II)-alcohol and nucleophilicity of the resultant zinc(II) hydroxide and zinc(II) alkoxide in double-functionalized complexes: theoretical studies on models for hydrolytic zinc enzymes

The factors governing the deprotonation ability of zinc(II)-water and zinc(II)-alcohol and nucleophilicity of the resultant zinc(II) hydroxide and zinc(II) alkoxide as complex models for zinc enzymes have been investigated through Hartree-Fock and density-functional theory methods with the 6-311++G(d,p) basis set. Our calculations showed that in these double-functionalized complexes (i.e., zinc complexes having both a zinc(II)-alcohol motif and a zinc(II)-water motif) zinc(II)-alcohol is preferred in deprotonation over zinc(II)-water (i.e., zinc(II)-alcohol has a much lower pK(a) than zinc-coordinated water in the same molecule). Natural bond orbital analysis revealed that zinc(II) alkoxides are more nucleophilic than their respective counterparts zinc(II) hydroxides. The analysis of the transition state in the transformation reaction from zinc(II) hydroxide species to zinc(II) alkoxide species indicates that zinc(II) alkoxides are the preferred deprotonated species not only thermodynamically but also kinetically. Further examination of the proposed mechanisms of the zinc(II) alkoxide-promoted transesterification path and the zinc(II) hydroxide-promoted hydrolysis path revealed the structures of the intermediates and energy diagrams in the reactions. These results, entitled double-functionalized complexes, for the first time, put a firm theoretical foundation of why the zinc(II)-alcoholic OH is a better model for hydrolytic zinc enzymes (having both stronger acidity and better nucleophilicity).     

Complex formation of polyethyleneimine with copper(II), nickel(II), and cobalt(II) ions

An influence of the structure of a globule of polyethyleneimine on the complex formation of one with the copper(II), nickel(II), and cobalt(II) ions is described. A change of the coordination number from the pH of solution for complexes of ethylenediamine, diethylenetriamine, and polyethyleneimine with metal ions was found. The fraction of monomer links, bound with metal ions, depends on the volume of the globule of macromolecule as well as the condition of the proceeding reaction. The reaction of complex formation is controlled by the diffusion of metal ions into the polymer globule in solution. The effective equilibrium constants of complex formation were found. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 914–922, 2002; DOI 10.1002/pola.10157     

Complexes formed between nickel(II), copper(II), zinc(II) and aspirin

Complexes of nickel(II), copper(II) and zinc(II) with aspirin have been prepared. Examination of the complexes of nickel(II) and zinc(II) indicates that they are salicylato complexes in which the aspirin has been de-ethanoylated.Chemical, spectral and magnetic properties show that the nickel(II) and copper(II) complexes have dimeric, octahedral structures while the zinc(II) complex has a tetrahedral structure. The decomposition of the complexes was studied by thermogravimetry and differential thermal analysis. Thermal decomposition products were obtained for the nickel(II) and zinc(II) complexes. Their structures are octahedral with the exception ofbis-salicyclic acid-zinc(II) which is tetrahedral.

---

Zusammenfassung Komplexe von Nickel (II), Kupfer (II) und Zink (II) mit Aspirin wurden hergestellt. Die Untersuchung der Koordinationsverbindungen von Nickel (II) und Zink (II) zeigt, daß dies Salycylatkomplexe sind, in welchen das Aspirin de-äthanoliert wurde.Die chemischen, spektralen- und magnetischen Eigenschaften zeigen, daß die Nickel (II)- und Kupfer (II)-Komplexe dimere Oktaederstrukturen besitzen, während der Zink (II)-Komplex eine Tetraederstruktur besitzt. Die Zersetzung der Komplexe wurde durch Thermogravimetrie und Differentialthermoanalyse untersucht. Thermische Zersetzungsprodukte der Nickel (II)- und Zink (II)-Komplexe wurden erhalten. Ihre Strukturen sind oktaedrich, mit Ausnahme vonBis-Salicyclosäure-Zink (II), dessen Struktur tetraedrisch ist.

---

(II), (II) (II) . (II) (II) , , , . . . , , , , . . . , - , .

     

Complex formation between manganese(II), cobalt(II), nickel(II), copper(II) and a series of new ligands derived from N,N′-O-phenylenebis(salicylideneimine)

A series of new ligands derived from N,N′-O-phenylenebis(salicylideneimine) have been synthesized and characterized by spectrometric methods. Their protonation constants and the stability constants of their complexes with Mn²⁺, Co²⁺, Ni²⁺ et Cu²⁺ have been determined by potentiometric methods in a water–ethanol (90:10 v/v) mixture at a 0.2 mol l⁻¹ ionic strength (NaCl) and at 25.0 ± 0.1 °C. The Sirko program was used to determine the protonation constants as well as the binding constants of both species [M(HL)]⁺ and [ML]. The stability order obtained is in agreement with Irving–Williams series.