Cyclen

Cyclen (1,4,7,10-tetraazacyclododecane) is an aza-crown ether with the formula (CH₂CH₂NH)₄. It is a white solid. It forms coordination complexes with metal cations and is used to synthesize the chelating agentDOTA which has several medical applications. Being structurally simple, symmetrical, and polyfunctional, cyclen has been widely investigated.