Cyclen frameworks

Zucchi, G. Ferrand, A.-C. Scopelliti, R. Btinzli, J.-C. G. Highly luminescent, visible-emitting lanthanide macrocyclic chelates stable in water and derived from the cyclen framework. Inorg. Chem. 2002, 41, 2459-2465. 

Since the introduction of Dotarem , a wealth of studies have been devoted to this complex and to complexes with coronands derived from the cyclen framework, both for contrast agent capability and, more recently, for analytical sensors based on relaxivity... 

One of the most popular macrocyclic frameworks for the design of BFCs is 1,4,7,10-tetraazacyclododecane (cyclen) which - if modified with side arms - results, e.g., in the structure of DOTA (O Fig. 45.3). As DOTA is known to form stable complexes with many radiometals as, e.g. In or Cu ", with all the lanthanides as well as with Bi " and Ac, it has been used, modified as BFC, for the radiolabeling of many biomolecules (Heppeler et al. 1999a, b Cutler et al. 2000 McDevitt et al. 2001 Hu et al. 2002). 

Faulkner and coworkers have used a ternary complex formation approach to bring about mixed Eu -Tb complexes. This work is based on kinetically stable cyclen D03A type frameworks and initially focused on the self-assembly of mononuclear Tb and Eu complexes where the charge neutral Eu complex contained a free carboxylic acid on the periphery of the complex (Figure 6), free to bind to the cationic Tb through electrostatic interactions. 

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