Stability constant, complex-formation

Stability constant of the MIP-analyte complex formation Stability constant of the NIP-analyte complex formation Ratio of the selectivity coefficients of the imprinted Cu2+ and non-imprinted Ni2+ polymers Analyte concentration Imaginary part of impedance... 

Table 2. Representative values of the dehydration rate constant and the complex formation rate constant for a singly and a doubly charged anionic ligand for several metals in aqueous solutions. An ionic strength of 0.01 mol dm 3 was assumed. T] is the half dissociation time (equivalent to O J/ka) for a singly charged anionic ligand with a stability constant of 106 dm3 mol. Based on [5,164,172]...

Complexes with succinate, glutarate and adipate have subnormal magnetic properties that indicate V-v-V interactions. Oxalato, malonato and maleato 1 1 complexes appeal monomeric as indicated by v(V=0) and and ease of formation, stability constants anc decrease in v(V=Q) follow the order oxalate>malonate>maleate. For the 1 2 complexes... 

The important difference between the dissociation mechanism of LnMEDTA complexes and the acid catalyzed dissociation of LnEDTA is the formation of mixed LnMEDTA-Ac" complex. The stability constants of such mixed complexes are small (1 to 10) and this may explain why such mixed complexes do not show up in the kinetics of dissociation or exchange of LnEDTA complexes. Further, in the present case [LnMEDTA]0 association with an acetate anion should be more favourable than [LnEDTA]- with an acetate anion based on electrostatic theory. Reference to Table 7.14 shows that Km values increase with increasing atomic number (decreasing radii) for heavy lanthanides but are independent for La-Nd series. 

Table 7.3 Formation ( = Stability) constants for EDTA and DTP A complexes with some essential and toxic metals (from Smith and Martell, 1974)...

An important characteristic of CyDs is the formation of inclusion complexes in both the solution and solid states, in which each guest molecule is surrounded by the hydro-phobic environment of the CyDs cavity. This can lead to the alteration of physicochemical properties of guest molecules, and can eventually have considerable pharmaceutical potential (Table 38.3). In the practical application of CyDs, attention should be directed towards the dissociation equilibrium and stoichiometry of the inclusion complex. When a CyD complex is dissolved in water or introduced into body fluids, it dissociates rapidly to free components in equilibrium with the complex. The stability constant (KJ is... 

Complex ion equilibria in solution are described by formation (stability) constants... 

The formation of fluoride complexes in aqueous NaCl solutions at various ionic strengths has been studied by potentiometric methods (Bilal et al., 1979 Bilal and Becker, 1979). Monofluoro and difluoro complexes are observed, but evidence is not found for higher fluoride complexes. The stability constants, 1, for the monofluoro complexes of La and Nd are 4.8 0.4 x 10 M, while those for Tb, Er and Lu are in the range 1.2-1.8 x 10 M . The /3i values vary with ionic strength. Stability constants, 2, for the difluoro complexes all increase monotonically across the rare earth series from 1.3 x 10 to 3.lxl0 M . The... 

Most group A metal ions have the electronic configuration of the rare gases, and the interaction of the metal with a ligand is primarily electrostatic in nature. Because the charge density (oc charge radius) is small, the water molecules are weakly held and the rate of their loss is comparable with the diffusion-controlled value of around 10 —10 s. The complex formation rate-constant for an ion in this group is therefore approximately equal to the maximum possible value, unless chelation steps are important, and the stability of the complex is reflected in the dissociation rate constant. 

TABLE 24.6 Stepwise and Overall Formation (Stability) Constants for Several Complex Ions ... 

The equilibrium constant for the formation of a complex ion is called a formation constant (or stability constant) and given the symbol Kf. A typical example is... 

The inverse of equation (28) gives us the stability constant or formation constant of the complex ion ... 

The stability of a complex is characterised by the stability constant (or formation constant) K ... 

Measurement of the stability constants of plutonium complexes is hampered by difficulties of maintaining a particular oxidation state. Formation of complexes of Pu+3, except in very acid solutions, is accompanied and often obscured by complexation catalyzed oxidation to Pu+lt. Study of complexation of Pu+lt is often confused by competition with hydrolysis above pH 1-2. 

Unfortunately, for ligands of strong acids, this equation may underestimate the stability constant as it calculates values for inner sphere formation only. Eigen (22) has proposed that the formation of complexes proceeds sequentially as follows ... 

The physical nature of the sulfate complexes formed by plutonium(III) and plutonium(IV) in 1 M acid 2 M ionic strength perchlorate media has been inferred from thermodynamic parameters for complexation reactions and acid dependence of stability constants. The stability constants of 1 1 and 1 2 complexes were determined by solvent extraction and ion-exchange techniques, and the thermodynamic parameters calculated from the temperature dependence of the stability constants. The data are consistent with the formation of complexes of the form PuSOi,(n-2)+ for the 1 1 complexes of both plutonium(III) and plutonium(IV). The second HSO4 ligand appears to be added without deprotonation in both systems to form complexes of the form PuSOifHSOit(n"3) +. ... 

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