Anhydrooligomers of o-aminobenzaldehydes—the rich chemistry of the Busch macrocycles

Abstract

This review concerns macrocyclic coordination compounds formed in the metal-templated self-condensation reactions of o-aminobenzaldehyde and its derivatives. Both cyclic trimers (TRI) and cyclic tetramers (TAAB), as well as the products of nucleophilic addition, are described. Several synthetic approaches for the preparations of these materials, as well as factors influencing the TAAB/TRI ratio, are summarized. The role of the ligand in the redox chemistry of the coordinated metal ion is discussed, as are the products of ligand reduction. TAAB and TRI complexes as well as H 2TAAB salts exhibit several types of unusual isomerism; these are described. A variety of spectroscopic techniques have been applied in the study of these materials and the important results are summarized. Recent advances concerning the biochemical and anticancer activity of the titled compounds, as well as their analytical applications, are also mentioned.