Chemists have been aware of the existence of coordination compounds con taining organic macrocyclic ligands since the first part of this century; however, only during the past few years have they expanded research into the chemistry of these compounds. The expansion was initiated in the early 1960s by the synthesis and characterization of compounds containing some new macrocyclic ligands. The synthesis of compounds which may serve as model systems for some natural products containing large rings as ligands provided the main goal for the early expansion of research effort; indeed, a recurrent...