Nitric oxide (NO) is a versatile molecule with a wide variety of functions in the human body, with involvement in vasodilation, cell signal transduction, and immune defense. However, some bacteria have developed an enzyme, flavodiiron NO reductase (FNOR), to counteract NO toxicity by binding and subsequently reducing nitric oxide to nitrous oxide (N2O). As a result, microbes equipped with FNORs show resistance to the human immune defense. Studying model complexes of the FNOR active site can provide insight into the structure and reactivity of the enzyme itself. This work focuses on second sphere coordination (SCS) effects in the FNOR active site, and their implementation in synthetic model complexes. In this way, I study the impact of SCS effects on NO binding and reduction. For this purpose, the ligand 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol (BPMP) was appended with tert-butyl amide groups to investigate the role of hydrogen bonding. The resulting ligand was metallated using two equivalents of iron (II) triflate in the presence of different equivalents of acetate as a bridging ligand, to make the corresponding diferrous complexes. These precursor compounds were then nitrosylated to form hs-{FeNO}7 diiron complexes, which were characterized by various spectroscopic techniques. N2O yields were obtained to understand the N-N coupling of the NO units at the diiron centers. X-ray crystallography plays a major role in structural characterization of these complexes prior to and after nitrosylation. This work shows that SCS effects from the tert-butyl amide moieties can play a pivotal role in NO coordination to diiron centers, which subsequently influences N-N coupling to form N2O. Future research includes the investigation of other diferrous BPMP derivatives to better understand how electronic and steric SCS effects impact the reactivities of these complexes.

Exploring secondary coordination sphere effects in flavodiiron nitric oxide reductase model complexes

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.