Multidentate complexing agents

In the treatment of nuclear waste for disposal, the practice has been to scavenge the radioactive nuclides by using multidentate complexing agents such as ethylenediaminete-... 

Some general examples of anion activation by different types of cation complex-ation are given in Eqs. (5-127)... (5-131). Among the specific multidentate complexing agents for cations are ... 

NMR STUDIES OF MICROSCOPIC SITES OF PROTONATION AND METAL-BINDING WITH MULTIDENTATE COMPLEXING AGENTS. 

NMR techniques have been used to indicate the time-average location of protons on multidentate complexing agents. For example, a proton spends an equivalent time on each of the nitrogens in symmetrical compounds such as ethylenediamine, EDTA, EGTA, etc. This conclusion is reached from the... 

The first part of this chapter is a review of the literature. It was written with the intent to summarize the important contributions that in situ derivatizations using multidentate complexing agents have made to the development of HPLC methods of analysis for metal species. The authors have not presented an exhaustive review of the literature. Rather, special consideration has been extended to those publications which describe innovative methods for separating metal cations, important applications, or studies concerned with elucidating retention mechanisms. The second and final part of this chapter deals with the mathematical language of complex equilibria and its implementation in designing separations for difficult samples of metal species. 

H02CCH2)2N-CH2 CH2-N(CH2C02H)2-An important compound, which owes its use to its sequestering properties. A multidentate chelating agent. Forms complexes with most elements. 

Favourable entropic effect generated by a multidentate chelating agent with respect to the complexation by monodentate ligands... 

Due to their pronounced selectivity in metal ion ccmplexation (6), crown ethers (macrocyclic polyethers) and related macrocyclic multidentate ligands are attractive mobile carriers for metal ion transport across liquid membranes. As summarized in recent reviews of macrocycle-facil itated transport of ions in liquid membrane systems (7,8), most studies have been conducted with macrocyclic carriers which do not possess ionizable groups. For such carriers, metal ions can only be transported down their concentration gradients unless some type of auxiliary complexing agent is present in the receiving aqueous phase. 

This is contrasted with the reaction of a complexing agent such as ammonia or thiourea with a metal ion such as Cu or Cu+, in which the complexing agent coordinates with only one reactive site on the metal ion. The formation of rings by the multidentate (many reactive sites) ligand gives added stability to the complex. The equilibrium for the reaction... 

The polyesters have then been transformed into their respective poly a-aminocarboxylic acids. These multidentate ligands poly-A propyleneglycine L- and DL- as well as poly-l-isopropyl-2-carboxyl-ethylenimine and poly-7V-ethylenealanine have then been examined as to their properties as metal complexating agents. The metal complexation stability constants of these polyampholytes are interpreted in the light of their structural differences, they show a four fold coordination with respect to the examined bivalent metal ions. Poly-A-piopyleneglycine has also been incorporated in cross-linked resin structures and the complexation behavior towards Zn, Cu, Ca and Mg has been determined. 

Multidentate ligand. Complexing agent used for titrimetric detn. of Fe. Sol. alkalis. 6.39 8.78 ... 

Multidentate synthetic chelating agents are used for the decontamination of nuclear reactors and for nuclear waste processing, because they form stable soluble complexes with many radionuclides. Unfortunately, their joint disposal has sometimes resulted in increased radionuclide mobility, with the concomitant contamination of groundwater. An attempt to lessen this problem involves degrading the chelating agents with bacteria (see Chapter 11). 

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