Mechanism of O-Atom Transfer from Nitrite: Nitric Oxide Release at Copper(II).

Nitric oxide (NO) is a key signaling molecule in health and disease. While nitrite acts as a reservoir of NO activity, mechanisms for NO release require further understanding. A series of electronically varied ß-diketiminatocopper(II) nitrite complexes [CuII](κ2-O2N) react with a range of electronically tuned triarylphosphines PArZ3 that release NO with the formation of O═PArZ3. Second-order rate constants are largest for electron-poor copper(II) nitrite and electron-rich phosphine pairs. Computational analysis reveals a transition-state structure energetically matched with experimentally determined activation barriers. The production of NO follows a pathway that involves nitrite isomerization at CuII from κ2-O2N to κ1-NO2 followed by O-atom transfer (OAT) to form O═PArZ3 and [CuI]-NO that releases NO upon PArZ3 binding at CuI to form [CuI]-PArZ3. These findings illustrate important mechanistic considerations involved in NO formation from nitrite via OAT.

Mechanochemical synthesis of ZnO.Al2O3 powders with various Zn/Al molar ratios and their applications in reverse water-gas shift reaction.

ZnO.Al2O3 powders with various Zn/Al molar ratios were prepared via a solid-state reaction using a mechanochemical synthesis method, and the selected powder with a ZnO/Al2O3 molar ratio of 1 was used as support for the preparation of 15% Ni/ZnO.Al2O3 catalyst. The activity of the prepared catalyst was studied in the reverse water-gas shift (RWGS) reaction. The synthesized samples were characterized by XRD, BET, TGA/DTA, TPR, FTIR, and SEM techniques. The results indicated that the prepared powders possessed mesoporous structure with pores having small diameters with crystallite sizes in the nanometer range (6.35-12.08 nm). The results showed that the increment in Zn/Al molar ratio reduced the BET area and the pure Al2O3 powder possessed the highest BET area (235.4 m2 g-1). The results also indicated that the rise of calcination temperature remarkably decreased the BET area. The prepared nickel-based catalyst also exhibited a high activity in RWGS reaction.

Nitric oxide release via oxygen atom transfer from nitrite at copper(ii).

Nitric oxide is a vital signaling molecule that controls blood flow and oxygenation and nitrite serves as an important reservoir for nitric oxide in biology. While copper containing enzymes are known to reduce nitrite to nitric oxide, herein we report a new pathway to release nitric oxide via oxygen atom transfer from nitrite at a copper(ii) site.