Stability constants determining

Table I Sample data for stability constant determination...

Cation-exchange techniques, stability constant determination of Pu sulfate... 

Pu sulfate complexes for stability constant determination reaction of Pu with diiodoethane. 42-43... 

Batch adsorption experiments by Yee and Fein (2002) using aqueous Cd, B. subtilis, and quartz as a function of pH showed that the thermodynamic stability constants, determined from binary systems, could successfully describe the distribution of Cd between the aqueous phase and the bacterial and mineral surfaces. The constants could also be used to estimate the distribution of mass in systems, and construct a surface complexation model. 

Bishydrated complexes formed with diethylenetriamine tetraacetate (DTTA4, Scheme 2) ligands attached to various scaffolds have been also investigated (35-37). The stability constants determined for the Gd11 (complexes formed with DTTA-chelators attached to a benzene or a bipyridine core were all in the range of... 

Table XIX contains stability constants for complexes of Ca2+ and of several other M2+ ions with a selection of phosphonate and nucleotide ligands (681,687-695). There is considerably more published information, especially on ATP (and, to a lesser extent, ADP and AMP) complexes at various pHs, ionic strengths, and temperatures (229,696,697), and on phosphonates (688) and bisphosphonates (688,698). The metal-ion binding properties of cytidine have been considered in detail in relation to stability constant determinations for its Ca2+ complex and complexes of seven other M2+ cations (232), and for ternary M21 -cytidine-amino acid and -oxalate complexes (699). Stability constant data for Ca2+ complexes of the nucleosides cytidine and uridine, the nucleoside bases adenine, cytosine, uracil, and thymine, and the 5 -monophosphates of adenosine, cytidine, thymidine, and uridine, have been listed along with values for analogous complexes of a wide range of other metal ions (700). Unfortunately comparisons are sometimes precluded by significant differences in experimental conditions.

Proton nmr halide anion titrations reveal that the ethyl- [79], propyl-[80] and butyl- [81] linked derivatives (Fig. 43) form complexes of 1 1 stoichiometry in acetonitrile solution. Stability constant determinations suggest that the ethyl derivative [79] exhibits selectivity for the chloride anion in preference to bromide or iodide. As the chain length increases, so the selectivity for chloride decreases and also the magnitude of the stability constant which is evidence for an anionic chelate effect with the chloride anion. Receptors containing larger aryl [81], [83], [84] and alkylamino spacers [85] (Fig. 43) form complexes of 2 1 halide anion receptor stoichiometry. 

This value should be treated with caution, as it is a conditional stability constant determined in a medium modeling blood plasma (Martin, R. B. Savory, J. Brown, S. Bertholf, R. L. Wills, M. R. Clin. Chem. 1987, 33, 405-107). 

The Cd ISE is used primarily in complexometric titrations with EDTA and Cd as an indicator [327,386] this approach is also the basis of stability constant determination [268,268a]. 

Stability constants represent primary data when considering a ligand type for use in a medical application. Stability constant determinations have been undertaken for the N4 donor macrocyclic ligand derivatives (180) and (18H with a range of divalent first-row transition and post-transition metal ions (including Mn )." In all cases the natural (Irving-Williams) stability order was observed to obtain for the 1 1 (M L) complexes. 

Redox potentials of pentacyanoferrates are often determined in association with kinetic and stability constant determinations. They are also available for 4-methyl- and 4-amino-pyri-dine pentacyanoferrates, and for [Fe(CS )5(2,6-dimethylpyrazine)] in acetonitrile-water mixtures.Oxidation potentials of [Fe(CN)5L] complexes correlate with the electron-withdrawing or -releasing properties of the ligands... 

STABILITY CONSTANT DETERMINATION BY A LINEAR PLOT METHOD... 

Methods used successfully for stability constant determinations are calorimetry (14—16), potentiometric measurements with ion-selective electrodes (3, 17), and certain spectroscopic techniques where favorable spectral properties are found (13, 18). Values of log K have also been deduced indirectly from conductance (19, 20) and potential measurements on phospholipid bilayers (21). Descriptions of these procedures... 

Stability constant determinations are few 1170 they are summarized in Table 100. Complexa-tion by acidic amino acids is obviously of relevance to the tanning of leather the stability constants for L-glutamic and aspartic acid1171 complexes are much greater than those for glycine or L-alanine.1172,1173,1174 This is probably because the acidic amino acids form tridentate complexes. In contrast, cysteine1173 appears to form glycine-like complexes in moderately acidic solution however, in the solid state L-cysteine is known to be tridentate vide infra). 

Stability constant determinations for complexes of Zn and Cd with various chelating azobenzenes show that zinc forms the stronger complexes.409... 

Stability constant determinations have been made on a range of monothio-jS-diketonato complexes in dioxane-water solution. The results indicate that (b) class metal ions form more stable complexes with monothio-/5-diketones than with /5-diketones. The stability sequence for monothio-/5-diketonato complexes is Cu > Ni > Zn > Cd > Pb.198 201... 

Thickness of the barrier layer, optimized at 220 nm [133], played a crucial role with respect to the chemosensor sensitivity, selectivity and LOD. So, eventually, the chemosensor architecture comprised a gold-film electrode, sputtered onto a 10-MHz resonator, coated with the poly(bithiophene) barrier layer, which was then overlaid with the MIP film. This architecture enabled selective determination of the amine at the nanomole concentration level. LOD for histamine was 5 nM and the determined stability constant of the MIP-histamine complex, XMn> = 57.0 M 1 [131], compared well with the values obtained with other methods [53, 136, 137]. Moreover, due to the adopted architecture, the dopamine chemosensor could determine this amine with the stability constant for the MIP-dopamine complex, XMip = (44.6 4.0) x 106 M-1 and LOD of 5 nM [133], which is as low as that reached by electroanalytical techniques [138]. The MIP-QCM chemosensor for adenine [132] also featured low, namely 5 nM, LOD and the stability constant determined for the MIP-adenine complex, XMIP = (18 2.4) x 104 M, was as high as that of the MIP-adenine complex prepared by thermo-induced co-polymer-ization [139]. The linear concentration range for determination of these amines extended to at least 100 mM. 

Fig. 1 Geometrical selectivity in the recognition of polyatomic anions by 71. Log K values of stability constants determined in an aqueous solution buffered at pH 8. Bite length refers to the distance of the two coordinating donor atoms of the ambidentate anion. Reproduced with permission from [49]...

The composition of these complexes and their stability constants have been determined for a large number of metal ions primarily with the use of emf methods (200, 201). The free hydrogen ion concentration and in some cases the free metal ion concentration are determined as functions of the stoichiometric hydrogen ion and metal ion concentrations. From measurements on series of solutions of different concentrations the number of metal atoms in a complex and its charge can be derived, but no information is obtained on the number of water molecules in the complex. Since emf measurements are influenced by changes in activity factors they have usually been done in an inert ionic medium of high concentration (3 M NaC104) and at low metal ion concentrations. The major complexes formed, however, have been found to be stable also in the concentrated solutions needed for X-ray diffraction measurements, and the stability constants determined seem to be... 

Thorium(IV) complexes of some catecholate, hydroxypyridonate, and desferri-oxamine ligands have been investigated and stability constants determined in connection with searches for sequestering agents for Pu4+.16... 

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