Photodecomposition of cis- and trans-2,4-dimethylcyclobutanones in the gas phase. Stereochemical inversion in the decarbonylation process and unimolecular lifetime of the hot ground state

1970 ◽  
Vol 92 (22) ◽  
pp. 6683-6685 ◽  
Author(s):  
Edward K. C. Lee ◽  
Howard A. J. Carless
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Cis And Trans

scholarly journals A Post-HF Approach to the Sunscreen Octyl Methoxycinnamate

2021 ◽  
Author(s):  
Ettore Fois ◽  
Mario Oriani ◽  
gloria tabacchi
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Stable Isomer ◽  
Dispersion Interactions ◽  
Trans Form ◽  
Compact Structure ◽  
Hartree Fock ◽  
Molecular Dispersion ◽  
Cis And Trans ◽  
Effect Of Light

Octyl methoxycinnamate (OMC) is a commercial sunscreen with excellent UVB filter properties. However, it is known to undergo a series of photodegradation processes that decrease its effectiveness as UVB filter. In particular, the trans (E) form - which is considered so far the most stable isomer - converts to the cis (Z) form under the effect of light. In this work, by using post-Hartree-Fock approaches (CCSD, CCSD(t) and CCSD+T(CCSD)) on ground state OMC geometries optimized at the MP2 level we show that the cis and trans form of the gas-phase OMC molecule have comparable stability. Our results suggest that the cis form is stabilized by intra-molecular dispersion interactions, leading to a folded, more compact structure than the trans isomer.<br>

scholarly journals A Post-HF Approach to the Sunscreen Octyl Methoxycinnamate

2021 ◽  
Author(s):  
Ettore Fois ◽  
Mario Oriani ◽  
gloria tabacchi
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Stable Isomer ◽  
Dispersion Interactions ◽  
Trans Form ◽  
Compact Structure ◽  
Hartree Fock ◽  
Molecular Dispersion ◽  
Cis And Trans ◽  
Effect Of Light

Octyl methoxycinnamate (OMC) is a commercial sunscreen with excellent UVB filter properties. However, it is known to undergo a series of photodegradation processes that decrease its effectiveness as UVB filter. In particular, the trans (E) form - which is considered so far the most stable isomer - converts to the cis (Z) form under the effect of light. In this work, by using post-Hartree-Fock approaches (CCSD, CCSD(t) and CCSD+T(CCSD)) on ground state OMC geometries optimized at the MP2 level we show that the cis and trans form of the gas-phase OMC molecule have comparable stability. Our results suggest that the cis form is stabilized by intra-molecular dispersion interactions, leading to a folded, more compact structure than the trans isomer.<br>

scholarly journals A Post-HF Approach to the Sunscreen Octyl Methoxycinnamate

2021 ◽  
Author(s):  
Ettore Fois ◽  
Mario Oriani ◽  
gloria tabacchi
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Stable Isomer ◽  
Dispersion Interactions ◽  
Trans Form ◽  
Compact Structure ◽  
Hartree Fock ◽  
Molecular Dispersion ◽  
Cis And Trans ◽  
Effect Of Light

Octyl methoxycinnamate (OMC) is a commercial sunscreen with excellent UVB filter properties. However, it is known to undergo a series of photodegradation processes that decrease its effectiveness as UVB filter. In particular, the trans (E) form - which is considered so far the most stable isomer - converts to the cis (Z) form under the effect of light. In this work, by using post-Hartree-Fock approaches (CCSD, CCSD(t) and CCSD+T(CCSD)) on ground state OMC geometries optimized at the MP2 level we show that the cis and trans form of the gas-phase OMC molecule have comparable stability. Our results suggest that the cis form is stabilized by intra-molecular dispersion interactions, leading to a folded, more compact structure than the trans isomer.<br>

scholarly journals Negative ion photoelectron spectroscopy confirms the prediction that D3h carbon trioxide (CO3) has a singlet ground state

2016 ◽  
Vol 7 (2) ◽  
pp. 1142-1150 ◽  
Author(s):  
David A. Hrovat ◽  
Gao-Lei Hou ◽  
Bo Chen ◽  
Xue-Bin Wang ◽  
Weston Thatcher Borden
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Photoelectron Spectroscopy ◽  
Radical Anion ◽  
Negative Ion ◽  
Singlet Ground State

The CO3 radical anion (CO3˙−) has been formed by electrospraying carbonate dianion (CO32−) into the gas phase.

The Dielectric Discharge as an Efficient Generator of Active Nitrogen for Chemiluminescence and Analysis

1983 ◽  
Vol 37 (6) ◽  
pp. 545-552 ◽  
Author(s):  
John Kishman ◽  
Eric Barish ◽  
Ralph Allen
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Band System ◽  
Electrothermal Atomization ◽  
Characteristic Radiation ◽  
Gaseous Species ◽  
Vibrationally Excited ◽  
Active Nitrogen ◽  
Excited Species ◽  
Intense Emission

A predominantly blue “active nitrogen” afterglow was generated in pure flowing nitrogen or in air by using a dielectric discharge at pressures from 1 to 20 Torr. The afterglow contains triplet state molecules and vibrationally excited ground state molecules. These species are produced directly by electron impact without the formation and recombination of nitrogen atoms. The most intense emission is the N2 second positive band system. The N2 first positive and N2+ first negative systems are also observed. The spectral and electrical properties of this discharge are discussed in order to establish guidelines for the analytical use of the afterglow for chemiluminescence reactions. The metastatic nitrogen efficiently transfers its energy to atomic and molecular species which are introduced into the gas phase and these excited species emit characteristic radiation. The effects of electrothermal atomization of Zn and the introduction of gaseous species (e.g., NO) on the afterglow are described.

scholarly journals Insights into the deactivation of 5-bromouracil after ultraviolet excitation

2017 ◽  
Vol 375 (2092) ◽  
pp. 20160202 ◽  
Author(s):  
Francesca Peccati ◽  
Sebastian Mai ◽  
Leticia González
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Surface Hopping ◽  
Ultraviolet Excitation ◽  
Quantum Chemistry Calculations ◽  
Electronic Structure Methods ◽  
Dna Strands ◽  
Potential Applications ◽  
Adiabatic Dynamics ◽  
Dynamics Simulations

5-Bromouracil is a nucleobase analogue that can replace thymine in DNA strands and acts as a strong radiosensitizer, with potential applications in molecular biology and cancer therapy. Here, the deactivation of 5-bromouracil after ultraviolet irradiation is investigated in the singlet and triplet manifold by accurate quantum chemistry calculations and non-adiabatic dynamics simulations. It is found that, after irradiation to the bright ππ * state, three main relaxation pathways are, in principle, possible: relaxation back to the ground state, intersystem crossing (ISC) and C–Br photodissociation. Based on accurate MS-CASPT2 optimizations, we propose that ground-state relaxation should be the predominant deactivation pathway in the gas phase. We then employ different electronic structure methods to assess their suitability to carry out excited-state dynamics simulations. MRCIS (multi-reference configuration interaction including single excitations) was used in surface hopping simulations to compute the ultrafast ISC dynamics, which mostly involves the 1 n O π * and 3 ππ * states. This article is part of the themed issue ‘Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces’.

Consistent characterization of the electronic ground state of Iron (II) Phthalocyanine from valence and core-shell electron spectroscopy

2021 ◽  
Author(s):  
Jonathan Laurent ◽  
John Bozek ◽  
Marc BRIANT ◽  
Pierre Carcabal ◽  
Denis Cubaynes ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Electron Spectroscopy ◽  
Organometallic Compound ◽  
Electronic Ground State ◽  
Core Shell ◽  
Shell Electron ◽  
Phthalocyanine Molecule ◽  
Electronic Ground

We studied the Iron (II) Phthalocyanine molecule in the gas-phase. It is a complex transition organometallic compound, for which, the characterization of its electronic ground state is still debated more...

STRUCTURAL, ELECTRONIC AND QSAR PROPERTIES OF THE CYFLUTHRIN MOLECULE: A THEORETICAL AM1 AND PM3 TREATMENT

2006 ◽  
Vol 17 (10) ◽  
pp. 1391-1402 ◽  
Author(s):  
EMİNE DENİZ ÇALIŞIR ◽  
ŞAKİR ERKOÇ
Keyword(s):  
Energy Level ◽  
Gas Phase ◽  
Ground State ◽  
Heat Of Formation ◽  
Tobacco Budworm ◽  
Vibrational Modes ◽  
Lumo Energy ◽  
Deciduous Fruit ◽  
Semi Empirical ◽  
Homo Energy Level

Cyfluthrin is a synthetic cyano-containing pyrethroid insecticide that has both contact and stomach poison action. It is a nonsystemic chemical used to control cutworms, ants, silverfish, cockroaches, mosquitoes, tobacco budworm and many others. Its primary agricultural uses have been for control of chewing and sucking insects on crops such as cotton, turf, ornamentals, hops, cereal, corn, deciduous fruit, peanuts, potatoes, and other vegetables. Cyfluthrin is also used in public health situations and for structural pest control. The structural, vibrational, electronic and QSAR properties of the cyfluthrin molecule in gas phase have been investigated theoretically by performing molecular mechanics method by using MM+ force field, and semi-empirical molecular orbital AM1 and PM3 calculations. The geometry of the molecule has been optimized, infrared spectrum (vibrational modes and intensities) and the electronic properties of the molecule have been calculated in its ground state. According to PM3 calculation, heat of formation of cyfluthrin molecule is about -48.58 kcal/mol (exothermic), which shows that this molecule thermodynamically be stable. The HOMO energy level for this molecule is found to be -9.701 eV and the LUMO energy level is -0.660 eV giving rise to a gap of 9.041 eV, which also indicates that cyfluthrin is thermodynamically stable.

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