scholarly journals Hydrogen transfer reaction: Bond formation and bond cleavage through the eyes of interacting quantum atoms

2019 ◽  
Vol 84 (8) ◽  
pp. 891-900
Author(s):  
Branislav Milovanovic ◽  
Mihajlo Etinski ◽  
Milena Petkovic
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Bond Cleavage ◽  
Bond Formation ◽  
Minimum Energy ◽  
Fragment Analysis ◽  
Interacting Quantum Atoms ◽  
Methoxy Radical ◽  
The One

Hydrogen transfer from hydroquinone to the methoxy radical was studied using the density functional theory. The energy decomposition technique, interacting quantum atoms, was employed for a detailed investigation of the changes that the bonds of interest go through along the minimum energy path in the vicinity of the transition state. The whole system was divided either into two or three fragments. The two-fragment analysis enabled investigation of the bond that is formed or the one that is cleaved by defining the fragments as reactants and as products, respectively. The three-fragment analysis (the fragments being semiquinone, hydrogen atom and methoxy radical) was used for the simultaneous analysis of the two phenomena, bond cleavage and bond formation. Additionally, it enabled the interaction between the particle that donates the hydrogen atom and the one that accepts it to be investigated. This interaction is characterized by attractive non-classical and repulsive classical interactions. It was demonstrated that the transferring hydrogen atom undergoes the most pronounced energy changes and gives the largest contribution to the deformation energy.

scholarly journals Exploring the effects of quantum decoherence on the excited-state dynamics of molecular systems

2021 ◽  
Vol 140 (4) ◽  
Author(s):  
Eric R. Heller ◽  
Jan-Ole Joswig ◽  
Gotthard Seifert
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Density Functional ◽  
Bond Cleavage ◽  
Minimum Energy ◽  
Quantum Decoherence ◽  
Ensemble Averaging ◽  
Excited State Dynamics ◽  
Complete Active Space ◽  
Related Compounds

AbstractFewest-switches surface hopping (FSSH) is employed in order to investigate the nonadiabatic excited-state dynamics of thiophene and related compounds and hence to establish a connection between the electronic system, the critical points in configuration space and the deactivation dynamics. The potential-energy surfaces of the studied molecules were calculated with complete active space self-consistent field and time-dependent density-functional theory. They are analyzed thoroughly to locate and optimize minimum-energy conical intersections, which are essential to the dynamics of the system. The influence of decoherence on the dynamics is examined by employing different decoherence schemes. We find that irrespective of the employed decoherence algorithm, the population dynamics of thiophene give results which are sound with the expectations grounded on the analysis of the potential-energy surface. A more detailed look at single trajectories as well as on the excited-state lifetimes, however, reveals a substantial dependence on how decoherence is accounted for. In order to connect these findings, we describe how ensemble averaging cures some of the overcoherence problems of uncorrected FSSH. Eventually, we identify carbon–sulfur bond cleavage as a common feature accompanying electronic transitions between different states in the simulations of all thiophene-related compounds studied in this work, which is of interest due to their relevance in organic photovoltaics.

Electronic Overlap Population as Reactivity Measure IV. Bond Cleavage and Bond Formation Processes

1976 ◽  
Vol 31 (7) ◽  
pp. 781-785
Author(s):  
S. Sharafi-Ozeri ◽  
L. Muszkat ◽  
K. A. Muszkat
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Carboxylic Acids ◽  
Sorbic Acid ◽  
Bond Cleavage ◽  
Bond Formation ◽  
Formation Processes ◽  
Overlap Population

Abstract Electronic overlap population is explored as a reactivity measure for several bond cleavage and bond formation processes. The reactions considered include: I. decarboxylation of carboxylic acids and of their anions; II. carbon-hydrogen bond cleavage in γ-radiolysis of glutaric, methyl-malonic and 3-hexendioic acids; and, III. hydrogen atom addition to butadiene and to sorbic acid.

Structure and bonding of 2,2,2-trichloroethylacetate: An experimental gas phase and computational study

2016 ◽  
Vol 71 (12) ◽  
pp. 1253-1260 ◽  
Author(s):  
Sebastian Blomeyer ◽  
Christian G. Reuter ◽  
Diego M. Gil ◽  
María E. Tuttolomondo ◽  
Aída Ben Altabef ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Density Functional ◽  
Dynamic Models ◽  
Computational Study ◽  
Structural Parameters ◽  
Interacting Quantum Atoms ◽  
The One ◽  
Gas Phase Structure

AbstractThe structural and conformational properties of 2,2,2-trichloroethylacetate, H3CCO2CH2CCl3, have been determined in the gas phase using gas electron diffraction (GED). The experimental measurements were complemented by MP2 and DFT quantum-chemical calculations. Two conformers separated by a shallow rotational barrier have been identified, one of C1 (syn-gauche) and the other of Cs symmetry (syn-anti). All calculations indicate that syn-gauche is preferred in terms of enthalpy, whereas syn-anti seems to be slightly more stable regarding Gibbs free energy. In the gas-phase structure determination, dynamic models based on different potential energy surface scans were used. The one from dispersion-corrected density functional theory, predicting a preference of syn-gauche by 1.7kJmol−1, was found to describe the experimental data best. One- and two-conformer models had to be rejected due to correlations and unrealistically large amplitudes. Experimentally determined structural parameters are in good agreement with both, quantum-chemical calculations as well as GED data for related compounds. Interacting quantum atoms (IQA) analyses revealed that interplay between the carbonyl group and the hydrogen as well as chlorine atoms of the trichloroethyl group accounts for most of the stabilisation of the C1 conformer. With intramolecular symmetry-adapted perturbation theory (I-SAPT) analyses it was possible to further elucidate the nature of dominant interactions in the two conformers. Herein, preference of syn-gauche can for the most part be attributed to electrostatic and to some extent to induction and dispersion interplays. In contrast this conformer is severely destabilised through steric repulsion. These results were supported by NBO analyses.

scholarly journals Theoretical Investigations of State Specific Hydrogen Atom Transfer in 8-Formyl-7-hydroxy-4-methylcoumarin

2022 ◽  
Vol 34 (2) ◽  
pp. 256-262
Author(s):  
K. Jagadeesha ◽  
Y.L. Ramu ◽  
T. Shivalingaswamy ◽  
M. Ramegowda
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Intramolecular Hydrogen Bonding ◽  
Hydrogen Atom Transfer ◽  
Vertical Excitation ◽  
Theoretical Investigations ◽  
Charge Analysis ◽  
Intramolecular Hydrogen ◽  
Hydroxyl Hydrogen

Excited state intramolecular hydrogen transfer (ESIHT) reaction of 8-formyl-7-hydroxy-4-methyl coumarin (FC) in its pure and hydrated state FC-(H2O)4 (FCH) has been studied by implementing state specific time dependent density functional theory (SS-TDDFT) along with the effective fragment potential (EFP1) method for solvation with discrete water molecules. The intramolecular hydrogen bond formed between hydroxyl hydrogen (H18) and formyl oxygen (O15) and intermolecular hydrogen bonds formed due to microsolvation were explored. The studies of electrostatic potential, natural charge analysis, difference electron density map and UV-Vis spectra of both FC and FCH molecules establish the intramolecular charge transfer (ICT) states of the molecules. The vertical excitation from S0 to S1 state causes the transfer of hydroxyl hydrogen to formyl oxygen and from S1 to S3 causes the transfer of the hydrogen atom back to hydroxyl oxygen. Potential energy surface scans along intramolecular hydrogen bonding at the ground and excited states confirm the state specific ESIHT reaction in both FC and FCH molecules.

scholarly journals Lowering the C-H Bond Activation Barrier of Methane Using SAC@Cu(111): A Periodic DFT Investigations

2021 ◽  
Author(s):  
Meema Bhati ◽  
Jignesh Dhumal ◽  
Kavita Joshi
Keyword(s):  
Density Functional ◽  
Bond Activation ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Minimum Energy ◽  
Value Added ◽  
Methane Activation ◽  
Single Atom ◽  
Activation Barriers ◽  
Metal Doped

Methane has long captured the world's spotlight for being the simplest and yet one of the most notorious hydrocarbon. Exploring its potential to be converted into value added products has raised a compelling interest. In the present work, we have studied the efficiency of Single-Atom Catalysts (SACs) for methane activation employing Density Functional Theory (DFT). The Climbing Image-Nudged Elastic Bond (CI-NEB) method is used in tandem with the Improved Dimer (ID) method to determine the minimum energy pathway for the first C-H bond dissociation of methane. Our study reported that the transition-metal doped Cu(111) surfaces enhance adsorption, activate C-H bond, and reduce activation barrier for first C-H bond cleavage of methane. The results suggest Ru/Co/Rh doped Cu(111) as promising candidates for methane activation with minimal activation barrier and less endothermic reaction. For these SACs, the calculated activation barriers for first C-H bond cleavage are 0.17 eV, 0.24 eV, and 0.26 eV respectively, which is substantially lower than 1.13 eV, the activation barrier for Cu(111).

scholarly journals Homolytic C-NO2 Bond Cleavage in Diaminodinitroethylene Isomers - A DFT Treatment

2020 ◽  
pp. 115-136
Author(s):  
Lemi Türker
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Quantum Chemical ◽  
Density Functional ◽  
Bond Cleavage ◽  
Chemical Properties ◽  
Bond Rupture ◽  
Homolytic Cleavage ◽  
Functional Theory ◽  
The One

Diaminodinitroethylene (DADNE) has three isomers including the well known geminal isomer, FOX-7. In the present study, the homolytic cleavage of one of the C-NO2 bonds of these isomers has been considered within the constraints of density functional theory at the level of UB3LYP/6-311++G(d,p). Transition states for that type of bond rupture are obtained. Various quantum chemical properties of the parent compounds and the decomposed systems are obtained, compared and discussed. Also the activation energies are calculated. The transition state originating from cis DADNE and the one from the geminal DADNE are found to be the most and least stable ones, respectively among the all.

Theoretical Study on the Antioxidant Activity of Alkannin and its Derivatives

2011 ◽  
Vol 138-139 ◽  
pp. 1056-1062
Author(s):  
Rui Fa Jin
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Bond Formation ◽  
Hydrogen Atom Abstraction ◽  
Hydrogen Bond Formation ◽  
Electron Transfer Mechanism ◽  
Electronic Delocalization ◽  
Structural And Electronic Properties ◽  
The One ◽  
Electron Donating Groups

The structural and electronic properties of alkannin and its derivatives and their radicals were investigated at density functional level. It turned out that the presence of the dihydroxy functionality increases the radical stability through hydrogen bond formation and favors hydrogen atom abstraction. The introduction of electron-donating groups for the molecules increases the activities of antioxidants. Moreover, alkannin and its derivatives appear to be good candidates for the one-electron-transfer mechanism. Their extended electronic delocalization between adjacent rings determines low ionization potential (IP) values, and it can be further improved by the introduction of the electron-donating groups for the molecules.

Nanometer Scale Spectroscopic Visualization of Catalytic Sites During a Hydrogenation Reaction on a Pd/Au Bimetallic Catalyst

2020 ◽  
Author(s):  
hao yin ◽  
Liqing Zheng ◽  
Wei Fang ◽  
Yin-Hung Lai ◽  
Nikolaus Porenta ◽  
...  
Keyword(s):  
Catalytic Hydrogenation ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Bimetallic Catalyst ◽  
Local Environment ◽  
Hydrogenation Reaction ◽  
Boundary Density ◽  
Catalytic Sites ◽  
Powerful Analytical Tool ◽  
Tip Enhanced Raman Spectroscopy

<p>Understanding the mechanism of catalytic hydrogenation at the local environment requires chemical and topographic information involving catalytic sites, active hydrogen species and their spatial distribution. Here, tip-enhanced Raman spectroscopy (TERS) was employed to study the catalytic hydrogenation of chloro-nitrobenzenethiol on a well-defined Pd(sub-monolayer)/Au(111) bimetallic catalyst (<i>p</i><sub>H2</sub>=1.5 bar, 298 K), where the surface topography and chemical fingerprint information were simultaneously mapped with nanoscale resolution (≈10 nm). TERS imaging of the surface after catalytic hydrogenation confirms that the reaction occurs beyond the location of Pd sites. The results demonstrate that hydrogen spillover accelerates hydrogenation at the Au sites within 20 nm from the bimetallic Pd/Au boundary. Density functional theory was used to elucidate the thermodynamics of interfacial hydrogen transfer. We demonstrate that TERS as a powerful analytical tool provides a unique approach to spatially investigate the local structure-reactivity relationship in catalysis.</p>

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