The 2nd-coordination sphere in metalloproteins plays an important role in regulating substrate binding and activation. The related hydrolytic enzymes Nitrile Hydratases (NHases) and Thiocyanate Hydrolase (SCNase) share conserved proximal serine and arginine residues that have been suggested to participate in proton shuttling and hydrogen bonding during catalysis. The active forms of the NHase/SCNases also contain sulfenate (RSO-) groups that are thought to be involved in water activation. The close proximity of these features to the substrate binding sites may help to organize a reactive cavity/hydration sphere affiliated with generation of an active HO- nucleophile and expulsion of catalysis products. As part of our continuing efforts to model the active sites and activities of NHases/SCNase, we synthesized and characterized several imidazole-thioether ligands containing bulky amide pendants in the imidazole 4-position to stabilize mononuclear complexes through H-bonding and steric interactions. Complexation with FeCl3 affords mononuclear species that have been characterized by x-ray crystallography, EPR and IR spectroscopy, and cyclic voltammetry. The results of these studies as well as an evaluation of their reactivity with various nitriles will be presented.

Synthesis, structure, and solution properties of bio-inspired iron complexes with functionalized imidazole donors

244th National Meeting (2012)

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