scholarly journals Cationic Effects on the Effective Hydrogen Atom Bond Dissociation Free Energy of High Valent Manganese Imido Complexes

2021 ◽  
Author(s):  
Nadia Leonard ◽  
Teera Chantarojsiri ◽  
Joseph Ziller ◽  
Jenny Yang
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Electric Fields ◽  
Hydrogen Atom Transfer ◽  
Bond Dissociation ◽  
Transfer Path ◽  
Reduction Potentials ◽  
Nitrido Complexes ◽  
Imido Complexes ◽  
High Valent

Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. There has been renewed interest on their use in molecular systems, where they can be installed using charged functionalities. Manga-nese(V) salen nitrido complexes (salen = N,N’-ethylenebis(salicylideneaminato)) appended with a crown ether unit con-taining a Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to experimen-tally demonstrate the effect of cation-induced electric fields on pKa, E1/2, and the effective bond dissociation free energy (BDFE) of N–H bonds. The series, which includes the manganese (V) salen nitrido without a crown appended, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were determined by UV-visible and 1H NMR spectroscopy. These values, together with the reduction potentials for the Mn(VI/V) couple measured by cyclic voltamme-try in acetonitrile, were used to calculated the N–H BDFEs of the imidos. Despite spanning >700 mV and >9 pKa units across the series, the hydrogen atom BDFE only spans ~ 5 kcal/mol (between 76 and 81 kcal/mol). These results suggest that incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa while minimally affecting BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer path-ways.

Hydrogen Atom Transfer Reaction Free Energy as a Predictor of Abiotic Nitroaromatic Reduction Rate Constants: A Comprehensive Analysis

2019 ◽  
Author(s):  
Dominic Di Toro ◽  
Kevin P. Hickey ◽  
Herbert E. Allen ◽  
Richard F. Carbonaro ◽  
Pei C. Chiu
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Energy Model ◽  
Second Order ◽  
Transfer Model ◽  
Atom Transfer ◽  
Order Rate ◽  
Linear Free Energy ◽  
Free Energy Model

<div>A linear free energy model is presented that predicts the second order rate constant for the abiotic reduction of nitroaromatic compounds (NACs). For this situation previously presented models use the one electron reduction potential of the NAC reaction. If such value is not available, it has been has been proposed that it could be computed directly or estimated from the electron affinity (EA). The model proposed herein uses the Gibbs free energy of the hydrogen atom transfer (HAT) as the parameter in the linear free energy model. Both models employ quantum chemical computations for the required thermodynamic parameters. The available and proposed models are compared using second order rate constants obtained from five investigations reported in the literature in which a variety of NACs were exposed to a variety of reductants. A comprehensive analysis utilizing all the NACs and reductants demonstrate that the computed hydrogen atom transfer model and the experimental one electron reduction potential model have similar root mean square errors and residual error probability distributions. In contrast, the model using the computed electron affinity has a more variable residual error distribution with a significant number of outliers. The results suggest that a linear free energy model utilizing computed hydrogen transfer reaction free energy produces a more reliable prediction of the NAC abiotic reduction second order rate constant than previously available methods. The advantages of the proposed hydrogen atom transfer model and its mechanistic implications are discussed as well.</div>

Experimental Validation of Hydrogen Atom Transfer Gibbs Free Energy as a Predictor of Nitroaromatic Reduction Rate Constants

2019 ◽  
Vol 53 (10) ◽  
pp. 5816-5827 ◽  
Author(s):  
Jimmy Murillo-Gelvez ◽  
Kevin P. Hickey ◽  
Dominic M. Di Toro ◽  
Herbert E. Allen ◽  
Richard F. Carbonaro ◽  
...  
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Gibbs Free Energy ◽  
Rate Constants ◽  
Experimental Validation ◽  
Reduction Rate ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer

Mechanistic insights into the reactions of hydride transfer versus hydrogen atom transfer by a trans-dioxoruthenium(vi) complex

2015 ◽  
Vol 44 (16) ◽  
pp. 7634-7642 ◽  
Author(s):  
Sunder N. Dhuri ◽  
Yong-Min Lee ◽  
Mi Sook Seo ◽  
Jaeheung Cho ◽  
Dattaprasad D. Narulkar ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Bond Activation ◽  
Hydride Transfer ◽  
Hydrogen Atom Transfer ◽  
Transfer Mechanism ◽  
Atom Transfer ◽  
High Valent

Valuable insights into the hydride-transfer mechanism and C–H bond activation reactions by high-valent trans-dioxoruthenium(vi) species is provided.

A High-Valent Iron–Oxo Corrolazine Activates C–H Bonds via Hydrogen-Atom Transfer

2012 ◽  
Vol 134 (17) ◽  
pp. 7392-7399 ◽  
Author(s):  
Kevin Cho ◽  
Pannee Leeladee ◽  
Amanda J. McGown ◽  
Serena DeBeer ◽  
David P. Goldberg
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
High Valent

Hydrogen Atom Transfer Reaction Free Energy as a Predictor of Abiotic Nitroaromatic Reduction Rate Constants: A Comprehensive Analysis

2019 ◽  
Author(s):  
Dominic Di Toro ◽  
Kevin P. Hickey ◽  
Herbert E. Allen ◽  
Richard F. Carbonaro ◽  
Pei C. Chiu
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Energy Model ◽  
Second Order ◽  
Transfer Model ◽  
Atom Transfer ◽  
Order Rate ◽  
Linear Free Energy ◽  
Free Energy Model

<div>A linear free energy model is presented that predicts the second order rate constant for the abiotic reduction of nitroaromatic compounds (NACs). For this situation previously presented models use the one electron reduction potential of the NAC reaction. If such value is not available, it has been has been proposed that it could be computed directly or estimated from the electron affinity (EA). The model proposed herein uses the Gibbs free energy of the hydrogen atom transfer (HAT) as the parameter in the linear free energy model. Both models employ quantum chemical computations for the required thermodynamic parameters. The available and proposed models are compared using second order rate constants obtained from five investigations reported in the literature in which a variety of NACs were exposed to a variety of reductants. A comprehensive analysis utilizing all the NACs and reductants demonstrate that the computed hydrogen atom transfer model and the experimental one electron reduction potential model have similar root mean square errors and residual error probability distributions. In contrast, the model using the computed electron affinity has a more variable residual error distribution with a significant number of outliers. The results suggest that a linear free energy model utilizing computed hydrogen transfer reaction free energy produces a more reliable prediction of the NAC abiotic reduction second order rate constant than previously available methods. The advantages of the proposed hydrogen atom transfer model and its mechanistic implications are discussed as well.</div>

Thermodynamics of Hydrogen Atom Transfer to a High-Valent Iron Imido Complex

2008 ◽  
Vol 130 (9) ◽  
pp. 2716-2717 ◽  
Author(s):  
Ismael Nieto ◽  
Feizhi Ding ◽  
Ranko P. Bontchev ◽  
Haobin Wang ◽  
Jeremy M. Smith
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
High Valent
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