Synthesis and properties of expanded cage complexes of Pt(IV), Pt(II), Co(III) and Cr(III)

Abstract

The thermodynamic, kinetic, redox and spectral properties of metal ion macropolycycles have been shown to differ dramatically from those of their mono-, di-, tri- and polydentate acyclic analogues. These properties depend on a combination of effects, including the ability of the ligand to adopt the preferred geometry of the metal ion (and vice versa), the match between the size of the metal ion and the cavity of the ligand and the type of ligating atoms. These effects may be systematically examined by subtly altering the ligand framework either by adding substituents, by expanding the cavity, or changing the donor atoms. Aspects of the behaviour are relevant to understanding some biological systems, namely, the stability of the metal ion coordinated in some biological ligands and the rapidity of some electron transfer reactions in proteins. This work explores the template synthesis of organic ligands about metal ions to form polyazamacrocyclic complexes. As the ligand essentially forms a cage about the metal ion, these complexes are hereafter referred to as "cage complexes".