Showing papers by "Somnath Ghosh published in 2023"
TL;DR: In this article , the acid-induced NO2− reduction chemistry of a nonheme FeII-nitrito complex, with variable amounts of H+, was investigated and showed that the amount of H2O2 decreases with increasing equivalents of H+ and entirely disappears when H+ reaches ≅ two-equiv.
Abstract: Nitrite reductase (NiR) catalyzes nitrite (NO2−) to nitric oxide (NO) transformation in the presence of an acid (H+ ions/pH) and serves as a critical step in NO biosynthesis. In addition to the NiR enzyme, NO synthases (NOSs) participate in NO production. The chemistry involved in the catalytic reduction of NO2−, in the presence of H+, generates NO with a H2O molecule utilizing two H+ + one electron from cytochromes and is believed to be affected by the pH. Here, to understand the effect of H+ ions on NO2− reduction, we report the acid-induced NO2− reduction chemistry of a nonheme FeII-nitrito complex, [(12TMC)FeII(NO2−)]+ (FeII–NO2−, 2), with variable amounts of H+. FeII–NO2− upon reaction with one-equiv. of acid (H+) generates [(12TMC)Fe(NO)]2+, {FeNO}7 (3) with H2O2 rather than H2O. However, the amount of H2O2 decreases with increasing equivalents of H+ and entirely disappears when H+ reaches ≅ two-equiv. and shows H2O formation. Furthermore, we have spectroscopically characterized and followed the formation of H2O2 (H+ = one-equiv.) and H2O (H+ ≅ two-equiv.) and explained why bio-driven NiR reactions end with NO and H2O. Mechanistic investigations, using 15N-labeled-15NO2− and 2H-labeled-CF3SO3D (D+ source), revealed that the N atom in the {Fe14/15NO}7 is derived from the NO2− ligand and the H atom in H2O or H2O2 is derived from the H+ source, respectively.
1 citations
TL;DR: In this article , the authors reported the nitric oxide dioxygenation (NOD) reactions of two MnIII-peroxo (MIII-O22-) complexes, bearing pentadentate ligands.
Abstract: Here, we report the nitric oxide dioxygenation (NOD) reactions of two MnIII-peroxo (MIII-O22-) complexes, [(3PYENMe)MnIII(O22-)]+ (1) and [(N3PY)MnIII(O22-)]+ (2), bearing pentadentate ligands. Complexes 1 and 2 give MnII-nitrate (MnII-NO3-) complexes (3 and 4) when reacted with nitric oxide (NO), respectively. The mechanistic study explored by using 2,4-di-tert-butylphenol (2,4-DTBP) suggested that the NOD reaction of 1 and 2 occurs via a presumed Mn-peroxynitrite ([Mn-PN]+, [Mn-ONOO-]+) intermediate. Tracking the source of N atoms using 15NO revealed that the N-atoms in MnII-NO3- (3 and 4) are derived from the 15NO moiety. Furthermore, we have explored the MIII-O22- regeneration from NOD products (3 and 4), and we have observed the formation of MIII-O22- complexes (1 and 2) upon treatment with KO2 or H2O2/triethylamine (TEA), respectively.
1 citations