Theoretical Perspectives on Redox “Non‐Innocent” Oxazolidine <i>N</i>‐Oxide Iron Nitroxide Complexes

Tewary, Subrata; Gass, Ian A.; Murray, Keith S.; Rajaraman, Gopalan

doi:10.1002/ejic.201201077

Cited by 17 publications

(25 citation statements)

References 69 publications

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“…The magnetic exchange interaction between O 2 C À and the Cr III ion is computed to be antiferromagnetic in nature (À1176.3 cm À1 ) and this suggests a triplet ground state for this species. [12] For this species a strong p-type interaction between the Cr(d xz ) and the oxygen p* orbital, and a relatively weak interaction between the Cr(d xy ) and oxygen p* orbital are estimated. These interactions are essentially a result of the nonlinear Cr III -O-O bond angle, and the non-orthogonality and strong mixing lead to a relatively strong antiferromagnetic interaction.…”

Section: Fementioning

confidence: 99%

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

Ansari¹,

Jayapal²,

Rajaraman³

2014

Angewandte Chemie

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Metal-superoxo species are ubiquitous in metalloenzymes and bioinorganic chemistry and are known for their high reactivity and their ability to activate inert CÀH bonds. The comparative oxidative abilities of M-O 2 C À species (M = Cr III , Mn III , Fe III , and Cu II ) towards CÀH bond activation reaction are presented. These superoxo species generated by oxygen activation are found to be aggressive oxidants compared to their high-valent metal-oxo counterparts generated by O···O bond cleavage. Our calculations illustrate the superior oxidative abilities of Fe III -and Mn III -superoxo species compared to the others and suggest that the reactivity may be correlated to the magnetic exchange parameter.Mononuclear metalloenzymes with coordinated oxygen at the metal center have applications in biology, industry, and the laboratory.[1] Oxygenated metal intermediates like oxo, peroxo, hydroperoxo, and superoxo species play a vital role in catalytic reactions such as hydrogenation, halogenation, hydroxylation, olefin epoxidation, and C À H bond activation.[2] In the last decade many high-valent metal-oxygen species have been studied to understand the fundamental structural, functional, and mechanistic aspects of their enzymes and their counterparts. [2a,d, 3] Apart from the metaloxo species, oxidation of CÀH bonds by several superoxometal complexes is also reported.[4] Unlike the metal-oxo species, the reactivity of M-O 2 C À species and their competing oxidative abilities are relatively less explored, although nature utilizes both species to carry out efficient catalysis. [5] Among other factors, the nature of the transition metals in M-O 2 C À species is also important, as it determines the electronic structure and the reactivity of these species. Over the years, the synthesis, structure, and reactivity of superoxo species containing copper, [6] iron, [5,7] and manganese [8] have been reported along with other metals.[9] An important addition to this class is the report of the crystal structure of the end-on Cr-O 2 C À species and kinetic studies to probe its ability to perform C À H bond activation in hydrocarbons. [10] Metal-superoxo species are generally transient in nature and are generated at the first step of the oxygen activation both in enzyme catalysis and in biomimetic chemistry. [7c, 10b] As these species are key intermediates in iron and copper catalysis, it suggests that the M-O 2 C À species perhaps play a larger role as an oxidant in enzyme catalysis. [6,11] In the M-O 2 C À species the unpaired electrons on the metal and the radical center are strongly coupled and the electronic configuration of the metal ions dictates the nature of the magnetic coupling (J) and this may in turn correlate to the CÀH bond activation. Here we have undertaken a detailed theoretical study to specifically address the following questions 1) probing the mechanism of C À H bond activation by Cr-O 2 C À and its comparative oxidative ability to high-valent metal-oxo species, 2) establishing the comparative oxidativ...

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Section: Fementioning

confidence: 99%

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

Ansari¹,

Jayapal²,

Rajaraman³

2014

Angewandte Chemie

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“…It is known that the DFT methods might misestimate the covalent character of metal-ligand bonds [81][82][83]. Although this is more frequently the case of transition metal coordination compounds, we decided to calculate the Dg tensors with a vast array of functionals (UBP86, UPBE, UOLYP, UB3LYP, UPBE0).…”

Section: G Tensormentioning

confidence: 99%

DFT insight into o-semiquinone radicals and Ca2+ ion interaction: structure, g tensor, and stability

Witwicki

Jezierska

2013

Theor Chem Acc

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Density functional theory methods were employed to elucidate the interactions between calcium ions and various o-semiquinone radicals mimicking the interactions occurring in biochemical systems. Predicted changes in the molecular and electronic structures of the radicals on Ca 2? coordination were correlated with the changes of g tensor and compared with those exerted by Mg 2? ions (reported by us previously). In order to broaden the insight into the differences between the Mg 2? and Ca 2?complexes, their relative stability was estimated on the basis of theoretically predicted Gibbs energies for the process of the complex formation.

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“…[22] A second study by the latter authors added to these three systems CASPT2 results for the [Fe II (N H S 4 )L] series, [23] which indicated that OLYP performed better than PBE0 (25 % HF exchange), B3LYP, and B3LYP*, although all four DFT methods give identical trends (vide infra). Ghosh and coworker also favour OLYP, albeit they tested it on somewhat different systems including Fe III porphyrins, [24,25] as do Tewary et al [26] for the interesting case of computing magnetic exchange interactions and their possible effects on SCO, which involves "non-innocent" oxazolidine N-oxide iron nitroxide complexes.…”

Section: Introductionmentioning

confidence: 99%

Spin‐State Energetics of Fe^II Complexes – The Continuing Voyage Through the Density Functional Minefield

Houghton

Deeth

2014

Eur J Inorg Chem

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Novel nanostructured sulfur (S)–carbide derived carbon (CDC) composites with ordered mesopores and high S content are successfully prepared for lithium sulfur batteries. The tunable pore‐size distribution and high pore volume of CDC allow for an excellent electrochemical performance of the composites at high current densities. A higher electrolyte molarity is found to enhance the capacity utilization dramatically and reduce S dissolution in S‐CDC composite cathodes during cycling.

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Theoretical Perspectives on Redox “Non‐Innocent” Oxazolidine N‐Oxide Iron Nitroxide Complexes

Cited by 17 publications

References 69 publications

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

DFT insight into o-semiquinone radicals and Ca2+ ion interaction: structure, g tensor, and stability

Spin‐State Energetics of Fe^II Complexes – The Continuing Voyage Through the Density Functional Minefield

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Theoretical Perspectives on Redox “Non‐Innocent” Oxazolidine N‐Oxide Iron Nitroxide Complexes

Cited by 17 publications

References 69 publications

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

DFT insight into o-semiquinone radicals and Ca2+ ion interaction: structure, g tensor, and stability

Spin‐State Energetics of FeII Complexes – The Continuing Voyage Through the Density Functional Minefield

Contact Info

Product

Resources

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Spin‐State Energetics of Fe^II Complexes – The Continuing Voyage Through the Density Functional Minefield