Evolution of strategies to prepare synthetic mimics of carboxylate-bridged diiron protein active sites

We present a comprehensive review of research conducted in our laboratory in pursuit of the long-term goal of reproducing the structures and reactivity of carboxylate-bridged diiron centers used in biology to activate dioxygen for the conversion of hydrocarbons to alcohols and related products. This article describes the evolution of strategies devised to achieve these goals and illustrates the challenges in getting there. Particular emphasis is placed on controlling the geometry and coordination environment of the diiron core, preventing formation of polynuclear iron clusters, maintaining the structural integrity of model complexes during reactions with dioxygen, and tuning the ligand framework to stabilize desired oxygenated diiron species. Studies of the various model systems have improved our understanding of the electronic and physical characteristics of carboxylate-bridged diiron units and their reactivity toward molecular oxygen and organic moieties. The principles and lessons that have emerged from these investigations will guide future efforts to develop more sophisticated diiron protein model complexes.

Graphical abstractExamples of synthetic analogs of carboxylate-bridged diiron cores in non-heme iron proteins that activate dioxygen for transport or hydrocarbon oxidation. A series of specialized ligands have been evolved to stabilize these units. Studies of the physical and chemical properties of the diiron complexes have enriched our understanding of their protein counterparts.Figure optionsDownload full-size imageDownload as PowerPoint slide