The development of compartmental macrocyclic Schiff bases and related polyamine derivatives

Abstract

The design and synthesis of [1 + 1], [2 + 2], [3 + 3] or [3 + 2] macrocyclic or macrobicyclic Schiff bases, the multiple self-condensation procedure between appropriate polyformyl- and polyamine-precursors or the templating capability of different metal ions in directing the synthetic pathway toward specific compounds are reported together with the use of transmetalation reactions of particular complexes with a different metal salt in order to obtain not otherwise accessible complexes. The reduction of the cyclic Schiff base or the reductive demetalation of the related complexes to the polyamine homologues is also considered. These systems can form mononuclear, homo- and heterodinuclear (or polynuclear) complexes, when reacted with appropriate metal salts. Attention is especially devoted to the physico-chemical and structural aspects of the resulting systems, especially the magneto-structural relationships arising from the interaction of paramagnetic ions, coordinated inside a unique moiety. The role of compartmental ligands, i.e. their ability to bind two or more metal ions in close proximity into two identical or different compartments, the presence of bridging groups inside these coordination moieties and their relevance in modulating the type and the extent of mutual interaction between the metal ions inside the adjacent chambers is also reviewed. The insertion of asymmetry into these ligands provides important diversification of the coordinating sites and allows for different and well defined recognition processes involving specific cations and/or anions at the adjacent sites.