Functional Models for Oxygen Activating Nonheme Monoiron Enzymes

With a large number of dioxygen-activating nonheme monoiron enzymes isolated and structurally characterized, small molecule synthetic compounds mimicking the structure and function of these enzymes have attracted great attention in synthetic inorganic chemistry. Over the years, considerable progress has been made in this area through the development of synthetic models. The structure and function of these model complexes helped in understanding of the respective enzymatic reaction and the intermediates involved in the catalytic cycle. This article outlines relevant examples of the functional models of nonheme monoiron enzymes developed in the last 15 years with primary focus on enzymes that catalyze CC and CH bond cleavage using dioxygen as the terminal oxidant. The biomimetic iron complexes that activate dioxygen and mimic the activities of aromatic ring cleaving oxygenases (catechol dioxygenases, 2-aminophenol dioxygenases and gentisate 1,2-dioxygenase), aliphatic CC bond cleaving oxygenases (2,4′-dihydroxyacetophenone dioxygenase, quercetin dioxygenases, acireductone dioxygenase and acetylacetone dioxygenase), cofactor-dependent oxygenases (α-ketoglutarate-dependent dioxygenases, α-hydroxy acid-dependent oxygenase, Rieske dioxygenases), and 1-aminocyclopropane-1-carboxylic acid oxidase are presented here. Some relevant functional model complexes based on other metal ions are also discussed.