Competitive complexing

COMPETITIVE COMPLEXING CALCULATING SPECIATION IN A MULTI-ION SOLUTION... 

J. Wang, B.S. Grabaric, Application of adsorptive stripping voltammetry for indirect measurement of nonelectroactive ions using competitive complex formation reactions, Mikrochim. Acta 100 (1990) 31-40. 

Cao, Y., Conklin, M. and Betterton, E. (1995) Competitive complexation of trace metals with dissolved humic acid. Environ. Health Persp., 103 (Suppl. 1), 29-32. 

The reaction control should be emphasized amongst the conditions of reactions of competitive complex formation [19,23], It is necessary to take into account that it is possible to determine, and frequently predict, the direction of the electrophilic attack to the donor center of di- and polyfunctional donors (ligands) only in the case when the thermodynamically stable products are formed under conditions of kinetic control. Thus, the thermodynamic stability of complexes is discussed, when the bond between the metal and di- and polydentate ligands is localized in the place of primary attack on one of any of the donor centers by the electrophilic reagent, without further change of coordination mode in the reaction of complex formation. 

Lopez, M.J., Arino, C., Dfaz-Cruz, S., Dfaz-Cruz, J.M., Tauler, R., and Esteban, M., Voltammetry assisted by multivariate analysis as a tool for complexation studies of protein domains competitive complexation of a and /J-metallothionein domains by cadmium and zinc, Environ. Sci. Technol., 37, 5609-5616, 2003. 

Final evidence for the involvement of a ground-state complex with [21] on the catalytic chemiluminescence pathway comes from the inhibition of the special catalysis by the addition of donor molecules capable of competitive complexation. Both the rate constant for the reaction of [21] catalyzed by MgTPP and the initial chemiluminescence intensity are decreased markedly by the addition of diethyl ether and even more dramatically by the addition of pyridine. This inhibition of catalysis apparently derives from complexation of the diethyl ether or pyridine to MgTPP. The added donor competes with [21] for the formation of the weak ground state complex, thereby inhibiting the otherwise effective catalysis. The special catalysis of ZnTPP and MgTPP is thus fully consistent with and readily accommodated by the CIEEL mechanism. 

Inskeep, W. P. and J. Baham. 1983. Competitive complexation of Cdll and Cull by water soluble organic ligands and Na-montmorillonite, Soil Sci. Soc. Am. J. 47 1109. 

An interesting templated bis-functionalization was reported by Shinkai and co-workers who introduced two boronic acid groups regio- and diastereo-selectively into C6o by using saccharides or saccharide derivatives as imprinting templates.147-149 Thus, when D-threitol was used as the template, C2-symmetric cis-3 isomers fC-49 and fA-49,150 were obtained in a nearly. 72 28 ratio after removal of the saccharide templates (Scheme 1.6).149 Competitive complexation studies indicated that D-threitol-imprinted boronic acid (fC)-49 and L-threitol-imprinted (A)-49 preferentially rebind their original templates with up to 48% d.e.148 Exploration of other regio- and diastere-oselective double [4 + 2] cycloadditions between C6o and o-quinodimethanes... 

Release of the Cu+ cation (step Hi of Figure 2.22) is performed by competitive complexation with the CN anion, which binds Cu+ avidly.6 This... 

Determined by competitive complexation methods. Measured in 5 1 acetone-d6 chloroform-d. Measured in 1 1 MeCN/chloroform at 23°C. 

This procedure, essentially based on competitive complexing of the ligand L by metal ions M and protons H+, has been used very extensively. " " ... 

Each of the intermediates in the preceding processes (equations 10-13), 1, 2, 4, and 5, involves coordinated cyclic structures that incorporate the cationic portion of the ion pair at the chain end. Thus, the extent of reactions 12 and 13, as well as the forward and reverse of reaction 11, should be sensitive to the polar nature and the spatial requirements of the countercation. These reactions, for example, might be suppressed by the presence of species more basic than siloxane that can competitively complex more strongly with the countercation (33). 

Deprotonated surface hydroxyls exhibit Lewis base behavior. Adsorption of metal ions is therefore understood as competitive complex formation involving one or two surface hydroxyl groups ... 

An important source of error in the quantification of PAHs is the ubiquitous presence of humic substances (HS) in natural waters (Kile et al., 1994). These substances have been shown to form associations with PAHs and as such to play an important role in PAH transport and fate in the environment (McCarthy and Jimenez, 1985 Kile et al., 1994 Kopinke et al., 2001). These interactions are the basis of competitive complex-ation that reduces the uptake of PAHs by solid phase extraction (Stum et al., 1998 Li and Kee Lee, 2001). This effect is illustrated in Figure 4.3.4 from Algarra et al. (2005), where the impact of humic substances is shown in a Stem-Volmer plot of the pyrene signal obtained by using the present method against the concentration of Suwanne River Humic acid. In addition to the humic substances many other organic substances and particulate matter may interact with PAHs and thus could significantly... 

Scheme 11 Competitive complexation, and photosensitized geometrical isomerization of cyclooctene within a p-cyclodextrin cavity.

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