Chelation chemistry

Three features of chelation chemistry are fundamental to most of the appHcations of the chelating agents. The first and probably the most extensively used feature is the control of free metal ion concentration by means of the binding—dissociation equiUbria. The second, often called the preparative feature, is that in which the special properties of the chelate itself provide the basis of the appHcation. The third feature comprises displacement reactions metal by other metal ions, chelant by chelant, and chelant by other ligands or ions. An appHcation may be termed defensive if an undesirable property in a process or product is mitigated, or aggressive if a new and beneficial property is induced. 

Use nonchelated process chemistries rather than chelated chemistries to reduce sludge... 

Dawson, P. Gadolinium Chelates Chemistry. In Textbook of Contrast Media, Dawson, P. Cosgrove, D. O. Grainger, R. G., Eds. Isis Medical Media Oxford, 1999 p 295. 

The aromatic and heteroaromatic thiosemicarbazones (39) are powerful chelating agents which have been rather neglected in the mainstream of chelation chemistry. Perrin and Stiinzi43) have reviewed their role as antiviral agents and noted their use in 1950 to reduce the severity of vaccinia infections of chick embryos and mice. The thiosemicarbazones have been used prophylactically to prevent outbreaks of smallpox in persons who had been in contact with the disease295). Pfauz96) has reviewed the pharmaceutical applications of thiosemicarbazones. 

Yokel RA. 1994. Aluminum chelation Chemistry, clinical, and experimental studies and the search for alternatives to desferrioxamine. J Toxicol Environ Health 41 131-174. 

For multistep complexation reactions and for ligands that are themselves weak acids, extremely involved calculations are necessary for the evaluation of the equilibrium expression from the individual species involved in the competing equilibria. These normally have to be solved by a graphical method or by computer techniques.26,27 Discussion of these calculations at this point is beyond the scope of this book. However, those who are interested will find adequate discussions in the many books on coordination chemistry, chelate chemistry, and the study and evaluation of the stability constants of complex ions.20,21,28-30 The general approach is the same as outlined here namely, that a titration curve is performed in which the concentration or activity of the substituent species is monitored by potentiometric measurement. 

Since the development of chelate chemistry has taken place almost wholly within the last three decades, the number of applications that have been found for this class of compounds is quite remarkable. Mail may not, however, take credit for the two most important uses of chelate compounds the use of the magnesium chelate, chlorophyll, as a catalyst for the incorporation of the hydrogen of water into plant systems and the use of the iron chelate, heme, as an oxygen carrier in human respiration. The ring system in both heme and chlorophyll is essentially that shown for copper porphyrin in Figure 22-4, but there are organic substituents on... 

Historically, the use of pyridine derivatives as cyclization substrates in the synthesis of fused heterocyclic systems has had great impact in pharmaceuticals, metal-chelation chemistry and other applications. Fused heterocycles incorporating different regioisomers... 

Aime, S., Botta, M., Fedeli, R, et al. (2001) High-relaxivity contrast agents for magnetic resonance imaging based on multisite interactions between a f -cyclodextrin oligomer and suitably functionalized Gdlll chelates. Chemistry - A European Journal, 7, 5261-5269. 

Wadas TJ, Wong EH, Weisman GR, Anderson CJ. Copper chelation chemistry and its role in copper radiopharmaceuticals. Curr. Pharm. Des. 2007 13 3-16. 

Studies on ionic hydration and complex formation reactions in solution in the 1960 s quite actively proceeded in Europe, especially in northern Europe. J. Bjerrum, a son of N. Bjerrum in Denmark, established a method for determination of stepwise formation constants of complexes with simple monodentate ligands in solution by the spectrophotomeffic method, which was soon modified to the method by potentiometry. Sillen in Sweden extended the method to polynuclear complex formation reactions and Schwartzenbach in Switzerland, who is a pioneer of chelate chemistry, applied this method to multidentate ligand complexes... 

Quite early on, investigations into the metal-chelating chemistry of the sapphyrins were carried out by Woodward and his group. However, only a few poorly characterized metal complexes resulted from these efforts, and these primarily involved first-row transition elements. For instance, these workers found that, when decamethyl sapphyrin was treated with the acetate salts of NP", Fe, ... 

C.E. Brown and W.E. Antholine. Chelation chemistry of carnosine. Evidence that mixed complexes may occur in vivo../. Phys. Chem., 83 (1979) 3314-3319. 

Mercaptoquinoline and its derivatives, chelate chemistry of 78MI8. Phosphorylated quinolines 86KGS1587. 

We are pleased to acknowledge the continuing collaboration of Dr. P. W. Durbin (Donner Laboratory, Lawrence Berkeley Laboratory) and her co-worker S. Sarah Jones. We thank the National Institutes of Health for supporting the biological Iron chelation chemistry reported here. The actinide sequestering project Is supported by the Division of Nuclear Sciences, Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. W-7405-Eng-48. 

A.E. Mattel, M. Calvin, Metal chelates chemistry (Chapter 5)... 

In particular, the interaction between transition metals and sugars provides many kinds of applications. They are observed not only in reactions such as catalytic chemistry [3-9], coordination and chelation chemistry [10-15], but also in analytical chemistry, such as during electrophoresis [16-18], NMR studies [19-22], and in many other fields [23-29]. 

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