Synthesis, characterization and reactivity of some macrobicyclic and macrotricyclic hetero-clathrochelate complexes

A variety of synthetic procedures, including organic reagents and templated metal ion reactions have led to new and interesting ligand sources. This review focuses principally on the preparation of macrobicyclic and macrotricyclic systems based upon a cyclam framework into which a wide range of cations can be incorporated. Emphasis is placed on ligand synthesis and characterization, particularly by X-ray crystallography, to confirm the location and coordination geometry of the encapsulated ions. The range of ligands described includes proton sponges, and frameworks containing different types of coordinating donors. Emphasis is placed on the formation of a tetraaza-(cyclam) base onto which are attached either one or two pendant rings. The resulting metal complexes show enhanced thermodynamic stability and kinetic inertness. Metal ions from various parts of the Periodic Table are used as examples of the ability of these ligands to form complexed ions and to accommodate differing coordination preferences of the ions. A short section is included on the redox properties of some transition metal ions, principally nickel and copper where stabilization of a higher oxidation state in the former leads to new chemistry not generally seen in mono-macrocyclic complexes. (C) 2002 Elsevier Science B.V. All rights reserved.