Macrocyclic ligand products, applications

After the separation of the actinides from the high-level waste, it is desirable to remove certain other fission products from the nuclear wastes. Some Cs and Sr are low-charged cations that react well with macro-cyclic ligands (e.g., crown ethers, calixarenes). Research to synthesize and investigate the properties of macrocyclic ligands for application in nuclear waste treatment has been an active effort internationally. Some of the results obtained are discussed in section 12.7. 

A wide range of nucleophiles has been shown to attack coordinated carbonyl compounds. The products depend upon the fate of the tetrahedral hydroxy intermediate formed. In the reaction of carbonyl compounds and amines the loss of water results in the formation of imines, and this methodology has widespread synthetic application. A novel sexidentate macrocyclic ligand (26) has been prepared by template methods. The formation of the hydrazone from hydrazine and... 

A less obvious part of the template concept is that, once formed, the products of these template reactions are not dependent on the template that guided in their generation. Thus, the macrocyclic ligands formed by template reactions of the kind shown in Fig. 2 can be removed from their metal ions and moved to other chemical applications. The great promise of the template effect rests on that fact. Templates facilitate the synthesis of complicated molecular architectures composed solely of the light atoms typical of organic molecules. 

Co-ordination of the ligand to the zinc activates it towards nucleophilic attack by ammonia and the product is the zinc complex of a conjugated dianionic tetraaza macrocycle (Fig. 8-35). This ligand is of some interest in forming a very stable lithium complex, derivatives of which have found some application in photoaddressable devices. 

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