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A multireference configuration interaction study of the photodynamics of nitroethylene.

Borges I, Aquino AJ, Lischka H - J Phys Chem A (2014)

Bottom Line: The vertical calculations mostly confirm the previous assignment of experimental spectrum and theoretical results using lower-level calculations.Based on the conical intersections found, a photochemical nonradiative deactivation process after a π-π* excitation to the bright S5 state is proposed.In particular, the possibility of NO2 release in the ground state, an important property in nitro explosives, was found to be possible.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química, Instituto Militar de Engenharia Praça General Tibúrcio , 80, 22290-270 Rio de Janeiro, Brazil.

ABSTRACT
Extended multireference configuration interaction with singles and doubles (MR-CISD) calculations of nitroethylene (H2C═CHNO2) were carried out to investigate the photodynamical deactivation paths to the ground state. The ground (S0) and the first five valence excited electronic states (S1-S5) were investigated. In the first step, vertical excitations and potential energy curves for CH2 and NO2 torsions and CH2 out-of-plane bending starting from the ground state geometry were computed. Afterward, five conical intersections, one between each pair of adjacent states, were located. The vertical calculations mostly confirm the previous assignment of experimental spectrum and theoretical results using lower-level calculations. The conical intersections have as main features the torsion of the CH2 moiety, different distortions of the NO2 group and CC, CN, and NO bond stretchings. In these conical intersections, the NO2 group plays an important role, also seen in excited state investigations of other nitro molecules. Based on the conical intersections found, a photochemical nonradiative deactivation process after a π-π* excitation to the bright S5 state is proposed. In particular, the possibility of NO2 release in the ground state, an important property in nitro explosives, was found to be possible.

No MeSH data available.


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Rigid MR-CISD potentialenergy curves for CH2 rotationaround the CC bond starting from the DFT/B3LYP//6-311G+(2df,2p) groundstate geometry.
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fig3: Rigid MR-CISD potentialenergy curves for CH2 rotationaround the CC bond starting from the DFT/B3LYP//6-311G+(2df,2p) groundstate geometry.

Mentions: Following the experiencewith the photodeactivation mechanisms found for ethylene31 and fluoroethylene,36 the MR-CISD potential energy curves of the states S0–S5 were calculated for two rigid torsions: of the NO2 group around the C–N bond (Figure 2) and of the CH2 group around the C=C bond (Figure 3); the latter torsion also occurs in ethylene.31 The MR-CISD CH2 out-of-plane bendingcurves (Figure 4) were also computed. In allcases, the calculations started from the DFT/B3LYP//6-311G+(2df,2p)ground state geometry.28


A multireference configuration interaction study of the photodynamics of nitroethylene.

Borges I, Aquino AJ, Lischka H - J Phys Chem A (2014)

Rigid MR-CISD potentialenergy curves for CH2 rotationaround the CC bond starting from the DFT/B3LYP//6-311G+(2df,2p) groundstate geometry.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4279882&req=5

fig3: Rigid MR-CISD potentialenergy curves for CH2 rotationaround the CC bond starting from the DFT/B3LYP//6-311G+(2df,2p) groundstate geometry.
Mentions: Following the experiencewith the photodeactivation mechanisms found for ethylene31 and fluoroethylene,36 the MR-CISD potential energy curves of the states S0–S5 were calculated for two rigid torsions: of the NO2 group around the C–N bond (Figure 2) and of the CH2 group around the C=C bond (Figure 3); the latter torsion also occurs in ethylene.31 The MR-CISD CH2 out-of-plane bendingcurves (Figure 4) were also computed. In allcases, the calculations started from the DFT/B3LYP//6-311G+(2df,2p)ground state geometry.28

Bottom Line: The vertical calculations mostly confirm the previous assignment of experimental spectrum and theoretical results using lower-level calculations.Based on the conical intersections found, a photochemical nonradiative deactivation process after a π-π* excitation to the bright S5 state is proposed.In particular, the possibility of NO2 release in the ground state, an important property in nitro explosives, was found to be possible.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Química, Instituto Militar de Engenharia Praça General Tibúrcio , 80, 22290-270 Rio de Janeiro, Brazil.

ABSTRACT
Extended multireference configuration interaction with singles and doubles (MR-CISD) calculations of nitroethylene (H2C═CHNO2) were carried out to investigate the photodynamical deactivation paths to the ground state. The ground (S0) and the first five valence excited electronic states (S1-S5) were investigated. In the first step, vertical excitations and potential energy curves for CH2 and NO2 torsions and CH2 out-of-plane bending starting from the ground state geometry were computed. Afterward, five conical intersections, one between each pair of adjacent states, were located. The vertical calculations mostly confirm the previous assignment of experimental spectrum and theoretical results using lower-level calculations. The conical intersections have as main features the torsion of the CH2 moiety, different distortions of the NO2 group and CC, CN, and NO bond stretchings. In these conical intersections, the NO2 group plays an important role, also seen in excited state investigations of other nitro molecules. Based on the conical intersections found, a photochemical nonradiative deactivation process after a π-π* excitation to the bright S5 state is proposed. In particular, the possibility of NO2 release in the ground state, an important property in nitro explosives, was found to be possible.

No MeSH data available.


Related in: MedlinePlus