Synthetic possibilities and strategies in the development of analogues for the dinuclear and polynuclear metal sites in enzymes and proteins

Two synthetic approaches in the synthesis of dinuclear (and polynuclear) coordination compounds are described briefly. The first method uses small external ligands (such as OH− and S2−) that act as a bridge to bring the metal ions together. The second method uses dinucleating chelating ligands to hold two metal ions fixed together, with one (or more) bridging donor groups between the metals. Application of these methods in the synthesis of model coordination compounds for superoxide dismutase (imidazole-bridged copper and zinc systems) and for hemocyanin (copper dimers with imidazole-type ligands) is described. It is found that the most stable dinuclear systems are formed when a dinucleating chelating ligand system is used.