Acetate complex stability constants

The measurement of stability constants of complexes of yttrium, lanthanide, and actinide ions with oxalate, citrate, edta, and 1,2-diaminocyclohexanetetra-acetate ligands has revealed that there is a slight increase in the stability of complexes of the /-electron elements, relative to the others. A series of citric acid (H cit) complexes of the lanthanides have been investigated by ion-exchange methods and the species [Ln(H2cit)]", [Ln(H2cit)2] , [Ln-(Hcit)], and [Ln(Hcit))2] were detected. Simple and mixed complexes of dl- and jeso-tartaric acid have been obtained with La " and Nd ions, and the stability constants of lactate, pyruvate, and x-alaninate complexes of Eu and Am " in water have been determined. 

The stability constants of complexes of metal ions with different ligands are to some degree correlated. Almost perfect linear correlation between stability constants of aqueous hydroxo complexes on the one hand and acetate (slope 0.27), lactate (slope 0.61) and salicylate (slope 1,29) complexes on the other has been demonstrated [669] for Fe, Pb, Cu, Zn, Co, Ni, Cd, Mn, and Mg. The adsorption process can be... 

Stability constants for calcium complexes of a selection of hydroxycarboxylate ligands are listed in Table VII (239,246,272-274). For tartrate, malate, and citrate stabilities decrease in the expected order Ca2+> Ba2+> Ra2+ (231,275). The stability constant for the complex of pyruvate (logiOifi 0.8 (273)) is similar to that for acetate calcium complexes of a-ketoglutarate and of oxaloacetate are somewhat more stable (logio-Ki = 1.3, 1.6 respectively (273)). The sequence logio-Ki = 3.0, 1.4, 1.1, 0.6 for the dicarboxylate ligands oxalate, malonate, succinate,... 

Stability constants, measured in methanol solution, for alkaline earth complexes of a number of ionophores are given in Table XVI (280,289,571-577).8 The values for the complexes of valinomycin and enniatin B lie between the values for the crown ethers 15C5 and 18C6 (cf. Section II.C.5 above), for the middle four entries the values are slightly higher. Stabilities of enniatin B complexes show a modest maximum for Ca2+, and of valinomycin complexes show stabilities increasing up to Ba2+ (281). LogAi values for the Ca2+ complexes of acetate, benzoate, and salicylate are between 4.5 and 4.7 in methanol (578) - the... 

Acetate complexes with Pu(III),Pu(IV) and Pu(VI). In the case of Pu(III) and Pu(IV) five acetate molecules interact with the cations. In the case of trivalent plutonium the stability constant of Pu(acetate) + has been estimated to be 5 x 1016(i<5) while that of tetravalent plutonium, Pu(acetate)j has been estimated to be between 8.06 x 1022 and 3,98 x 1022 (18). Evidence indicates that Pu(VI) forms mono, di-, tri- and tetra-acetate complexes (19). 

The cadmium complexes were also investigated potentiometrically. Using this method, the complexes of cadmium with asparagine [128], taurine [129], A -(6-ami-no-3-methyl-5-nitroso-4-oxo-3,4-dihydro-pyrimidin-2-yl)glycine [130], succinate and malate [131], acetate at different temperatures [132], pyridine oxime ligands [133], 2-hydroxypropene-l,3-diamine-Af,Af,Af, A -tetraacetic acid [134] were studied. The stoichiometry and stability constants of these complexes were determined. 

Recently, Grenthe [407] compared the stability constants for the acetate, glycolate and thioglycolate (mercaptoacetate) complexes of Eu3+ and Am3+ (fi — 0.5 at 20° C), and obtained the following log k values... 

Powell et al. [412] recently prepared the JnVlactates from Nd to Lu and obtained them as trihydrates. They also measured the stability constants of the lactate complexes but at lower ionic strength (p = 0.1 at 20° C) and obtained somewhat larger values for log ki (cf. acetate complexes at different ionic strengths). 

The complexation properties of the macrocyclic, spider-like tetraaza-tetraace-tate ligand DOTA were found by Desreux to be very unique [45]. The stability constants of the complexes Ln(DOTA)- are very high and both the formation and dissociation rates are unusually low. The behavior of the DOTA- analogous ligands containing at least three acetate and three or four methylene-phospho-nate or methylene-phosphinate groups is very similar, and a number of new derivatives have been synthesized and investigated in order to develop new CAs. 

In order to calculate [Eu3+]f (eqn. (12)) three different euro plum - acetate complexes have to be considered EuAc2, EuAco, and EuAc3, the corresponding stability constants being 101 79, 103 11 and 101 21, respectively, (26)corresponding to a correction factor Q = 8.48. 

Other groups have subsequently reported anion receptors that work on the same principle. For instance, an Eu(III) complex of the bis-bipyridinephen-ylphosphine oxide ligand 86 made by Ziessel and co-workers is able to sense anions by luminescence enhancement in acetonitrile, with stability constants which follow the trend fluoride>acetate>chloride>nitrate [61]. Tsukube and co-workers have investigated the properties of the Eu(III) and Tb(III) complexes of the chiral ligand 87 [62]. Anion binding was assessed by profiling luminescence enhancement in acetonitrile, and it was found that the different metal centres provided different selectivities. The emission at 548 nm of the Tb(III) complex was increased by 5.5 times in the presence of 3 equivalents of chloride compared to 2.2 for nitrate and 1.1 for acetate. Conversely the emission at 618 nm of the Eu(III) complex was increased 8.3 times by 3 equivalents of nitrate, 2.5 times for chloride and 1.0 times for acetate. Stability constants were not reported. 

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