Role of ancillary ligands in -nitrosothiol and NO generation from nitrite-thiol interactions at mononuclear zinc(ii) sites.

Generation of -nitrosothiol (RSNO) and nitric oxide (NO) mediated by zinc(ii) coordination motifs is of prime importance for understanding the role of zinc(ii)-based cofactors in redox-signalling pathways. This study uniquely employs a set of mononuclear [LZn] cores (where L = MePzPz/MePzPy/MePzQu) for introducing subtle alterations of the primary coordination sphere and investigates the role of ligand tuning in the transformation of NO in the presence of thiols. Single crystal X-ray diffraction (SCXRD) analyses on [LZn-X](X) (where X = perchlorate/triflate) illustrate consistent changes in the bond distances, thereby showing variations of the metal-ligand interactions depending on the nature of the heterocyclic donor arms (pyrazole/pyridine/quinoline).

Nitrite and Nitric Oxide Interconversion at Mononuclear Copper(II): Insight into the Role of the Red Copper Site in Denitrification.

Nitrite (NO ) and nitric oxide (NO) interconversion is crucial for maintaining optimum NO flux in mammalian physiology. Herein we demonstrate that [L Cu (nitrite)] moieties (in 2 a and 2 b; where, L = Me PzPy and Me PzQu) with distorted octahedral geometry undergo facile reduction to provide tetrahedral [L Cu ] (in 3 a and 3 b) and NO in the presence of biologically relevant reductants, such as 4-methoxy-2,6-di-tert-butylphenol (4-MeO-2,6-DTBP, a tyrosine model) and N-benzyl-1,4-dihydronicotinamide (BNAH, a NAD(P)H model). Interestingly, the reaction of excess NO gas with [L Cu (MeCN) ] (in 1 a) provides a putative {CuNO} species, which is effective in mediating the nitrosation of various nucleophiles, such as thiol and amine.

Metal-free Transformations of Nitrogen-Oxyanions to Ammonia via Oxoammonium Salt.

Transformations of nitrogen-oxyanions (NO ) to ammonia impart pivotal roles in sustainable biogeochemical processes. While metal-mediated reductions of NO are relatively well known, this report illustrates proton-assisted transformations of NO anions in the presence of electron-rich aromatics such as 1,3,5-trimethoxybenzene (TMB-H, 1 a) leading to the formation of diaryl oxoammonium salt [(TMB) N =O][NO ] (2 a) via the intermediacy of nitrosonium cation (NO ). Detailed characterizations including UV/Vis, multinuclear NMR, FT-IR, HRMS, X-ray analyses on a set of closely related metastable diaryl oxoammonium [Ar N =O] species disclose unambiguous structural and spectroscopic signatures.