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  • 1
    Electronic Resource
    Electronic Resource
    Modeling of a CdII-N-(2-hydroxyethyl)ethylenediamine system and optimization of stability constants by the use of complex formation curves. A polarographic study at a fixed L:M ratio and varied pH (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 1167-1173 
    Details
    ISSN: 1040-0397
    Keywords: Speciation ; DPP ; Polarographic complex formation curves ; Labile metal complexes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ligand N-(2-hydroxyethyl)ethylenediamine (HEEN) was studied with CdII by differential pulse polarography (DPP) at fixed total ligand (LT) to total metal (MT) concentration ratios and varied pH at 25°C and an ionic strength μ = 0.5 mol dm-3. The polarographic experimental complex formation curve (ECFC) and calculated complex formation curve (CCFC) were used for modeling of the metal-ligand system and the refinement of stability constants. The ECFC, in which experimental parameters of polarographic peaks are included (a shift in a peak potential and a variation in a peak height) appears to be a characteristic function for a particular metal-ligand system studied at a particular LT : MT ratio. The CCFC is a theoretical curve calculated for the assumed metal-ligand model from mass-balance equations. The final model of metal species formed is the one for which the CCFC fits best the ECFC. Four cadmium complexes CdL2+, CdL22+, CdL32+, and CdL2 (OH)+ and their stability constants as log β found from DPP 5.08 ± 0.03, 9.44 ± 0.04, 11.25 ± 0.05, 12.06 ± 0.03, respectively, are reported. The complex CdL32+ was found for the first time. Results obtained in this work are compared with literature data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140091507
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental and calculated complex formation curves as an optimization tool in speciation studies of polarographically labile metal-ligand systems (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 699-706 
    Details
    ISSN: 1040-0397
    Keywords: DPP ; Speciation ; Labile metal complexes ; Complex formation curves ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The PbII-N,N′-di-2-picolylethylenediamine (DPA-2) system was studied by differential pulse polarography (DPP) and glass electrode potentiometry (GEP) at fixed total-ligand to total-metal concentration ratio and varied pH. The polarographic experimental complex formation curve (ECFC) and calculated complex formation curve (CCFC) are used for modeling of a metal-ligand system and the refinement of stability constants. The ECFC is used instead of a shift in the peak potential plotted vs. pH and it appears to be a characteristic function for a particular metalligand system. The CCFC is a theoretical curve calculated for the assumed metal-ligand model from mass-balance equations. The final model of metal species formed is the one which is accepted by these two experimental techniques and for which stability constants of metal complexes obtained from DPP and GEP differ the least. Four lead complexes Pb(HL), PbL, PbL2(OH) and PbL(OH)2 and their stability constants as log β found from DPP 12.67 ± 0.08, 9.68 ± 0.07, 16.12 ± 0.08 and 14.88 ± 0.06, respectively, are reported. Results obtained from GEP and DPP differ only within experimental errors typical for these techniques.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140090909
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  • 3
    Electronic Resource
    Electronic Resource
    Pulse polarography study of the complexes of lead with azacrown [2,2,2]cryptand in the presence of an excess of competing sodium ion (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 763-769 
    Details
    ISSN: 1040-0397
    Keywords: Lead ; Azacrown cryptand ; Complexation ; Pulse polarography ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential pulse polarography (DPP) has been used to determine the formation constants of PbII at ionic strength 0.5 M and 25 °C with [2, 2, 2]cryptand in the presence of 0.5 M sodium nitrate. The equilibrium between Pb2+ and the ligand is established slowly on the polarographic time scale, so that two well-separated peaks are observed, that for the metal ion and for a nonlabile ML complex for which the stability constant was found to be log K1 = 12.9. The equilibrium between the ML complex and hydroxide ion appeared to be fast and a substantial shift in the peak potential of the ML complex was observed. Two labile lead complexes are reported, namely ML(OH) and ML(OH)2 for which stability constants (log β) were found to be 20.51 and 23.75, respectively. The Lingane equation has been modified to allow calculation of formation constants for labile complexes of lead with two ligands, [2, 2, 2]cryptand and OH-. A single, second, overall protonation constant of [2, 2, 2]cryptand at an ionic strength of 0.5 M and 25°C in the presence of 0.5 M Na+ is reported and its value was found to be log β2 = 18.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070815
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    Paper (German National Licenses)
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