Deciphering the mechanism of O reduction with electronically tunable non-heme iron enzyme model complexes.

A homologous series of electronically tuned 2,2,2-nitrilotris(-arylacetamide) pre-ligands ( ) were prepared (R = NO, CN, CF, F, Cl, Br, Et, Me, H, OMe, NMe) and some of their corresponding Fe and Zn species synthesized. The iron complexes react rapidly with O, the final products of which are diferric mu-oxo bridged species. The crystal structure of the oxidized product obtained from DMA solutions contain a structural motif found in some diiron proteins. The mechanism of iron mediated O reduction was explored to the extent that allowed us to construct an empirically consistent rate law. A Hammett plot was constructed that enabled insightful information into the rate-determining step and hence allows for a differentiation between two kinetically equivalent O reduction mechanisms.