Synthesis and coordination chemistry of topologically constrained azamacrocycles

Bridging superstructures added to small azamacrocycles, through the accompanying additional topological constraint, enhance the characteristic that makes azamacrocycles indispensable ligands for transition metal coordination including biomimetic chemistry: high complex stability. This review begins by briefly revisiting the coordination chemistry concepts leading to this advantage over less topologically complex ligands. Then, it details the approaches used to synthesize such bridged azamacrocycles, including direct organic synthesis, the use of templates, protection/deprotection chemistry, and various condensation reactions. The example of a specific ligand type and its transition metal complexes, which are useful for biomimetic applications, illustrates the potential of the field and lead to some general conclusions. # 2002 Elsevier Science B.V. All rights reserved.