Rapid nitrite reduction enabled by secondary sphere hydrogen bonds within non-heme iron complexes.

A non-heme iron(ii) complex bearing a ligand with secondary sphere hydrogen bond (H-bond) donors, (tris(6-phenylaminopyridylmethyl)amine, TPA, rapidly reduces nitrite (NO ) to nitric oxide (NO) in the absence of exogenous additives, affording a Fe(iii)(μ-O) diamond core. An electronically analogous complex containing a ligand without H-bonds (tris(6-methylpyridylmethylamine), TPA, also reduces NO to NO and forms an Fe(iii)(μ-O) core, but is four orders of magnitude slower, highlighting the impact of H-bonds to promote NO reduction. We compare the structural and spectroscopic differences of the two Fe(iii)(μ-O) complexes and show that H-bonding interactions weaken the Fe-O bonds, perturb the electronic structure of the FeO cores, and thereby engender distinct reductive stability profiles.