Yttrium macrocyclic complexes

L.M. Vallarino, Macrocycle complexes of the lanthanide(III) yttrium(III) and dioxouranium(VI) ions from metal-templated syntheses 443... 

MACROCYCLIC COMPLEXES OF THE LANTHANIDE(III), YTTRIUM(III) AND DIOXOURANIUM(VI) IONS FROM METAL-TEMPLATED SYNTHESES... 

Macrocyclic complexes of the lanthanide (III) and yttrium(III) ions with pyridine head-units and aliphatic side-chains... 

It is by now well established that all lanthanide (III) ions, as well as the yttrium(III) and uranyl ions, are effective templates for the synthesis of macrocyclic complexes the scarcity of information on similar systems involving 5f-block elements other than uranium appears to be due to lack of investigation rather than to any intrinsic failure of these elements to function as templates in macrocyclic syntheses. 

The vast majority of the macrocyclic complexes of the lanthanide(III), yttrium(III) and uranyl ions obtained so far by metal-templated synthesis are of the Schiff-base type even the few known examples of simple polyamine complexes actually result from the cyclic condensation of a diamine with a (modified) carbonyl precursor. In general, the metal-templated synthesis is facilitated by the presence of oxygen-donor anions, such as nitrate, acetate, or trifluoromethylsulfonate lanthanide(III) thiocyanates have also been successfully used. With a few exceptions, the outcome of the synthesis appears to be independent of the order of addition of the reactants. No deliberate attempts have been made to investigate the detailed mechanism of these metal-templated cyclic condensation reactions. 

Vallarino LM, Leif RC (1997) Macrocycle complexes of yttrium, the lanthanides and the actinides having peripheral coupling functionalities continuation-in-part. US Patent 5,696,240... 

DOTA is of particular interest as a BFC for radiolabeling of small BMs with yttrium and lanthanide isotopes. The macrocyclic framework is well organized so that it forms yttrium and indium complexes with high thermodynamic stability and kinetic inertness. The pXa values of the carboxylic groups are in the range 2-5. Lower pKa values result in less competition from protons, high stability of the metal complex, and minimum acid-assisted demetallation, even... 

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