Polyazacycloalkanes are cyclic molecules containing nitrogen atoms and having a strong affinity towards metallic cations. The most known tetraazacycloalkanes are the 9, 12 and 14 membered rings respectively called TACN, cyclen and cyclam.
Theses molecules can be functionalized on the nitrogen and/or the carbon atoms. Indeed, the affinity of tetraazacycloalkanes towards specific cations can be modulated by changing the nature, the number and the relative position of the functional groups. Moreover, many applications require the synthesis of macrocycles bearing two kinds of functional groups (bifunctional chelating agent): one for the coordination of the metal and the other for the anchoring onto a solid support (silica gel, organic polymers) or a macromolecule (antiboby, protein).