Computational Mechanistic Insights on the NO Oxidation Reaction Catalyzed by Non-Heme Biomimetic Cr-N-Tetramethylated Cyclam Complexes.

Tiziana Marino,Marirosa Toscano,Maria Grazia Fortino,Nino Russo,Marta Erminia Alberto

doi:10.3390/ijms20163955

Tiziana Marino, Marirosa Toscano + Show 3 more

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https://doi.org/10.3390/ijms20163955

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Abstract

The conversion reaction of NO to NO3− ion catalyzed by the end-on [Cr(III)(n-TMC)(O2)(Cl)]+ superoxo and side-on [Cr(IV)(n-TMC)(O2)(Cl)]+ peroxo non-heme complexes (n = 12, 13, 14 and 15), which are biomimetic systems of nitric oxide dioxygenases (NODs), has been explored using a computational protocol in the framework of density functional theory. Results show that the potential energy profiles for the studied reactions lie above the reagent energies, regardless of the used catalyst. Both the O-O bond breaking in the biomimetics and the NO3− ion formation require low energy barriers suggesting an efficient catalytic power of the studied systems. The rate-determining step depends on ligand size.

Highlights

Oxidation reactions play an important role in different fields from biochemistry to industrial processes to organic synthesis.In many metabolic processes, oxidation of organic substrates by dioxygen (O2 ) is mediated by metal containing active sites, a great deal of attention has been paid to the catalytic cycles ofO2 activation by heme and non-heme metalloenzymes [1]
The considerable interest towards heme iron-oxy catalytic species lies in obtaining information which is transportable to non-heme natural and synthetic complexes
Of particular interest appear to be the studies on mononuclear metal complexes, including chromium, iron, cobalt, nickel and copper ion with O2 -derived ligands bearing N-tetramethylated cyclam (TMC) chelates [1,3,4,5,6,7,8,9]

Summary

Introduction

Oxidation reactions play an important role in different fields from biochemistry to industrial processes to organic synthesis.In many metabolic processes, oxidation of organic substrates by dioxygen (O2 ) is mediated by metal containing active sites, a great deal of attention has been paid to the catalytic cycles ofO2 activation by heme and non-heme metalloenzymes [1]. Oxidation reactions play an important role in different fields from biochemistry to industrial processes to organic synthesis. Oxidation of organic substrates by dioxygen (O2 ) is mediated by metal containing active sites, a great deal of attention has been paid to the catalytic cycles of. The considerable interest towards heme iron-oxy catalytic species lies in obtaining information which is transportable to non-heme natural and synthetic complexes. Recent advances in synthetic non-heme model chemistry have allowed to gain insights about the reactivity and the structural and physicochemical properties of the metal-oxygen intermediates, generated in the active sites of different oxidases and oxygenases [2]. The TMC ligands are intensively used in biomimetic inorganic chemistry [1,3,4,10] due to their ability to modulate the binding mode of the O2 to the metal center and to influence its preferred oxidation state

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