Molecular Devices Based on Metallocyclam Subunits

Publisher Summary This chapter explains that metal complexes of cyclam derivatives, including scorpionands, can perform some elementary functions at the molecular level (signalling, sensing, controlling of molecular motions). These, and other, functions result from the combination of the unique properties displayed by cyclam and related synthetic macrocycles. Cyclam (1,4,8,11-tetra-aza-cyclotetradecane, 3) is the prototype of synthetic aza-macrocycles. It tends to encircle transition metal ions to give complexes of trans-octahedral geometry, which display some peculiar properties: (i) high thermodynamic stability (the thermodynamic macrocyclic effect); (ii) extreme inertness to demetallation (the so-called kinetic macrocyclic effect); (iii) rich redox activity of the metal centre and stabilization of unusually high oxidation states: Ni III , Cu III , Ag II and Ag III and, as a transient, Hg III . The chapter discusses various properties that make cyclam and its metal complexes convenient and versatile subunits for building multicomponent systems displaying a variety of functions. The 2-substituted positional isomer is expected to favor the coordination of the nitro–nitronate group to transition metal centre, encircled by the cyclam ring.