Non-innocent ligands in bioinorganic chemistry—An overview

This review touches the most common instances where non-innocent (“suspect”) behaviour of redox-active ligands, either substrates or supporting components, is observed in a biochemical context. These ligands include the O2/O2−/O22−, NO+/NO/NO−, o-quinone/o-semiquinone/catecholate and tyrosyl/tyrosinate redox systems, the tetrapyrrole (porphyrinic) ligands, the pterins and flavins, and the dithiolene/ene-dithiolate ligands in molybdo- and tungstopterin. These non-innocent ligands are discussed in their interaction with biological iron, copper, manganese, molybdenum or tungsten centers.