ABSTRACT
In polynuclear complexes, electronic interactions between redox-active metal fragments linked by bridging ligands is evidenced by a separation between metalcentred redox couples and the subsequent formation of stable mixed-valence states. Such behaviour is a function of the length, substitution pattern and conformation of the bridging ligand. Magnetic exchange interactions between metals in polynuclear complexes are also dependent on the nature of the pathway linking the metal ions [1]. If the metal-based magnetic orbitais are sufficiently close to overlap directly, then the nature of the magnetic interaction depends on their relative symmetry [2] and this has been exploited in the preparation of complexes with predictable magnetic properties [1,3]. If however the magnetic orbitais are too far apart to overlap directly, but require the participation of bridging ligand orbitais to mediate the interaction (a super-exchange process), then the properties of the bridging ligand become as important as they are in mediating electronic interactions. This principle has received relatively little systematic attention for metal complexes, in contrast to extensive work on organic polyradicals whose magnetic properties are a function of structure and topology [4].
