scholarly journals DFT analysis into the intermediates of nickel pyridinethiolate catalysed proton reduction

2015 ◽  
Vol 44 (32) ◽  
pp. 14333-14340 ◽  
Author(s):  
Carolyn N. Virca ◽  
Theresa M. McCormick
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Catalytic Cycle ◽  
Proton Reduction ◽  
Functional Theory ◽  
Water Reduction

The catalytic cycle of the water reduction catalyst, nickel pyridine 2-thiolate, has been investigated using Density Functional Theory.

scholarly journals Theoretical Calculations on the Mechanism of Enantioselective Copper(I)-Catalyzed Addition of Enynes to Ketones

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 359 ◽  
Author(s):  
Hanwei Li ◽  
Mingliang Luo ◽  
Guohong Tao ◽  
Song Qin
Keyword(s):  
Density Functional Theory ◽  
Steric Hindrance ◽  
Phenyl Ring ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Dft Method ◽  
Catalytic Cycle ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Chiral Systems

Computational investigations on the bisphospholanoethane (BPE)-ligated Cu-catalyzed enantioselective addition of enynes to ketones were performed with the density functional theory (DFT) method. Two BPE-mesitylcopper (CuMes) catalysts, BPE-CuMes and (S,S)-Ph-BPE–CuMes, were employed to probe the reaction mechanism with the emphasis on stereoselectivity. The calculations on the BPE-CuMes system indicate that the active metallized enyne intermediate acts as the catalyst for the catalytic cycle. The catalytic cycle involves two steps: (1) ketone addition to the alkene moiety of the metallized enyne; and (2) metallization of the enyne followed by the release of product with the recovery of the active metallized enyne intermediate. The first step accounts for the distribution of the products, and therefore is the stereo-controlling step in chiral systems. In the chiral (S,S)-Ph-BPE–CuMes system, the steric hindrance is vital for the distribution of products and responsible for the stereoselectivity of this reaction. The steric hindrance between the phenyl ring of the two substrates and groups at the chiral centers in the ligand skeleton is identified as the original of the stereoselectivity for the titled reaction.

scholarly journals Theoretical study on the mechanism of iridium-catalyzed γ-functionalization of primary alkyl C–H bonds

2016 ◽  
Vol 94 (12) ◽  
pp. 1028-1037 ◽  
Author(s):  
Zhe Li ◽  
Miaoren Xia ◽  
Russell J. Boyd
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Experimental Observation ◽  
Density Functional ◽  
Theoretical Study ◽  
Reductive Elimination ◽  
Catalytic Cycle ◽  
Catalyst Precursor ◽  
Functional Theory ◽  
Initial Formation

The mechanism of the iridium-catalyzed functionalization of a primary C–H bond at the γ position of an alcohol 5 is investigated by density functional theory (DFT) calculations. A new IrIII–IrV mechanism is found to be more feasible than the previously reported IrI–IrIII mechanism. 10 In the IrIII–IrV mechanism, the reaction begins with the initial formation of (Me4phen)IrIII(H)[Si(OR)Et2]2 from the catalyst precursor, [Ir(cod)OMe]2 (cod = 1,5-cyclooctadiene). The catalytic cycle includes five steps: (1) the insertion of norbornene into the Ir–H bond to produce (Me4phen)IrIII(norbornyl)[Si(OR)Et2]2 (R = –CH(C2H5)C3H7); (2) the Si–H oxidative addition of HSi(OR)Et2 to form (Me4phen)IrVH(norbornyl)[Si(OR)Et2]3; (3) the reductive elimination of norbornane to furnish (Me4phen)IrIII[Si(OR)Et2]3; (4) the intramolecular C–H activation of the primary C–H bond at the γ position; and (5) the Si–C reductive elimination to produce the final product and regenerate the catalyst. The highest barrier in the IrIII–IrV mechanism is 7.3 kcal/mol lower than that of the IrI–IrIII mechanism. In addition, the regioselectivity of the C–H activation predicted by this new IrIII–IrV mechanism is consistent with experimental observation.

Density functional theory (DFT) and combined quantum mechanical/molecular mechanics (QM/MM) studies on the oxygen activation step in nitric oxide synthase enzymes

2009 ◽  
Vol 37 (2) ◽  
pp. 373-377 ◽  
Author(s):  
Sam P. de Visser
Keyword(s):  
Nitric Oxide ◽  
Density Functional Theory ◽  
Cytochrome P450 ◽  
Density Functional ◽  
Catalytic Cycle ◽  
Theoretical Studies ◽  
Cytochrome P450 Enzymes ◽  
Compound I ◽  
Functional Theory ◽  
Oxide Synthase

In this review paper, we will give an overview of recent theoretical studies on the catalytic cycle(s) of NOS (nitric oxide synthase) enzymes and in particular on the later stages of these cycles where experimental work is difficult due to the short lifetime of intermediates. NOS enzymes are vital for human health and are involved in the biosynthesis of toxic nitric oxide. Despite many experimental efforts in the field, the catalytic cycle of this important enzyme is still surrounded by many unknowns and controversies. Our theoretical studies were focused on the grey zones of the catalytic cycle, where intermediates are short-lived and experimental detection is impossible. Thus combined QM/MM (quantum mechanics/molecular mechanics) as well as DFT (density functional theory) studies on NOS enzymes and active site models have established a novel mechanism of oxygen activation and the conversion of L-arginine into Nω-hydroxo-arginine. Although NOS enzymes show many structural similarities to cytochrome P450 enzymes, it has long been anticipated that therefore they should have a similar catalytic cycle where molecular oxygen binds to a haem centre and is converted into an Fe(IV)-oxo haem(+•) active species (Compound I). Compound I, however, is elusive in the cytochrome P450s as well as in NOS enzymes, but indirect experimental evidence on cytochrome P450 systems combined with theoretical modelling have shown it to be the oxidant responsible for hydroxylation reactions in cytochrome P450 enzymes. By contrast, in the first catalytic cycle of NOS it has been shown that Compound I is first reduced to Compound II before the hydroxylation of arginine. Furthermore, substrate arginine in NOS enzymes appears to have a dual function, namely first as a proton donor in the catalytic cycle to convert the ferric-superoxo into a ferric-hydroperoxo complex and secondly as the substrate that is hydroxylated in the process leading to Nω-hydroxo-arginine.

Ensemble Effects on Allylic Oxidation within Explicit Solvation Environments

2021 ◽  
Author(s):  
Hung Minh Le ◽  
Mariano Guagliardo ◽  
Anne E. V. Gorden ◽  
Aurora Clark
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Density Functional ◽  
Umbrella Sampling ◽  
Catalytic Cycle ◽  
Allylic Oxidation ◽  
Functional Theory ◽  
Sampling Density ◽  
Ensemble Effects ◽  
Explicit Solvation

Umbrella-sampling density functional theory molecular dynamics (DFT-MD) has been employed to study the full catalytic cycle of the allylic oxidation of cyclohexene using a Cu(II) 7-amino-6-((2-hydroxybenzylidene)amino)quinoxalin-2-ol complex in acetonitrile to...

Catalytic oxidation of CO by N2O on neutral Y2MO5 (M = Y, Al) clusters: a density functional theory study

RSC Advances ◽  
2015 ◽  
Vol 5 (93) ◽  
pp. 76651-76659 ◽  
Author(s):  
Hong-Ling Fang ◽  
Lei Xu ◽  
Jia Li ◽  
Bin Wang ◽  
Yong-Fan Zhang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Co Oxidation ◽  
Catalytic Oxidation ◽  
Density Functional ◽  
Catalytic Cycle ◽  
Current Work ◽  
Density Functional Theory Study ◽  
Oxidation Of Co ◽  
Functional Theory ◽  
Catalytic Oxidation Of Co

The full catalytic cycle of CO oxidation by N2O on neutral Y2MO5 (M = Y, Al) clusters has been studied in the current work.

Mechanistic Studies of Cp*Ir(III)/Cp*Rh(III)-Catalyzed Branch-Selective Allylic C–H Amidation: Why is Cp*Ir(III) Superior to Cp*Rh(III)?

2021 ◽  
Author(s):  
Nan Ma ◽  
Zheyuan Liu ◽  
Jianhui Huang ◽  
Yanfeng Dang
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Catalytic Cycle ◽  
Mechanistic Studies ◽  
Functional Theory

Density functional theory calculations have revealed the mechanism and origins of reactivity and regioselectivity of the Cp*Ir(III)/Cp*Rh(III)-catalyzed allylic C–H amidation of alkenes and dioxazolones. Generally, the catalytic cycle consists of...

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