Theoretical study of the trans -stilbene isomerization reaction in ethane

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Isotope effect in normal-to-local transition of acetylene bending modes J. Chem. Phys. 136, 014304 (2012); 10.1063/1.3673570Rotational isomerism of acetic acid isolated in rare-gas matrices: Effect of medium and isotopic substitution on IR-induced isomerization quantum yield and cis→trans tunneling rate This paper presents a continuation of our previous theoretical studies on the rate of isomerization of trans-stilbene from the first excited electronic state based on the potential energy surface of Vachev et al. ͓J. Phys. Chem. 99, 5247 ͑1995͔͒. Harmonic RRKM computations and molecular dynamics and Monte Carlo based classical rates are presented for deuterated isotopes of stilbene as well as hexane clusters of stilbene of varying size. Good agreement with experiment is found for energy dependent rates of d 12 vs h 12 stilbene. However, we find that the rate for d 2 stilbene is greater than for d 10 stilbene in contradiction to the experimental observations. For the hexane clusters we find that addition of hexane molecules causes a systematic decrease in the rate, in agreement with experiment.

Section: Introductionsupporting

confidence: 56%

“…We modified it slightly 22 so that it gave an activation energy for the excited state reaction which agrees with the experimental measurement. In Ref.…”

Section: Introductionmentioning

confidence: 71%

Section: B Resultsmentioning

confidence: 99%

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Isomerization of stilbene in the gas phase: Theoretical study of isotopic and clustering effects

Gershinsky

Pollak

1997

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“…Another approach, to construct a potential-energy surface suitable to reproduce selected spectroscopic data, has recently been conducted. [13][14][15][16] However, this procedure has little predictive power, since the desired results are put in previously, and then reproduced. Moreover, Eli Pollak and co-workers [17][18][19][20] apply sophisticated theories, based on transition state theory, to the photoisomerization of trans-stilbene.…”

Section: Introductionmentioning

confidence: 99%

Viscosity dependence and solvent effects in the photoisomerization of cis-stilbene: Insight from a molecular dynamics study with an ab initio potential-energy function

Berweger

Gunsteren

Müller‐Plathe

1999

Isomerization of trans-stilbene: Theory for pressure dependence of the rate J. Chem. Phys. 108, 9186 (1998); 10.1063/1.476365 Molecular dynamics simulation with an ab initio potential energy function and finite element interpolation: The photoisomerization of cis-stilbene in solution Molecular-dynamics simulations of the photoisomerization of cis-stilbene in supercritical argon were performed. The stilbene molecule is represented by ab initio quantum chemistry, while the solvent, the interaction with solvent, and the time evolution were described by classical mechanics. Reaction rate constants are estimated and their dependence on temperature, pressure, and viscosity are investigated. Agreement with available experimental data was obtained. Our simulations strongly suggest a minimum on the excited-state potential-energy surface at a gauche conformation which is very rapidly reached after excitation, which leads to nonequilibrium barrier transitions. Specific solvent effects were identified. Implications on the current opinion on stilbene photoisomerization are discussed.

“…The Stilbene isomerization reaction has attracted the attention of the research community for a long time and is a subject of extensive experimental and theoretical investigations. 16 In a recent series of papers, 9,17,18 using classical methods, we have shown that molecular dynamics on a ''good'' potential energy surface leads to excellent agreement between experiment and theory. We could thus resolve the long standing puzzle for the relation between experimentally measured gas phase and liquid phase rates which suggested that the liquid enhances the rate by a factor of ϳ20.…”

Section: Introductionmentioning

confidence: 99%

Quantum harmonic transition state theory—Application to isomerization of stilbene in liquid ethane

Gershinsky

Pollak

1998

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A harmonic quantum transition state theory, suggested recently by Pollak and Gershinsky ͓in Lectures on Stochastic Dynamics, edited by W. Lutz and T. Poeschel, Lecture Notes in Physics ͑Springer Verlag, New York, 1997͔͒, is applied for the first time to a realistic reacting system. The isomerization of trans-stilbene in the gas phase and in the presence of dense liquid ethane solvent is investigated. We find that the overall quantum effect at room temperature is rather small. The quantum correction to the classical reaction rate estimate is approximately 23% for gas phase stilbene at room temperature. The addition of the dense solvent lowers the correction down to 13%, thus making the reacting system even more ''classical,'' justifying the extensive use of classical molecular dynamics in investigating this reaction.