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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.


Related in: MedlinePlus

Computed g- and h-vectorsof the conical intersections found. (a)MR-CISD MXS (S1/S0), (b) CASSCF MXS (S2/S1), and (c) MR-CISD MXS (S3/S2). The arrows are not to scale between different pictures.
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fig7: Computed g- and h-vectorsof the conical intersections found. (a)MR-CISD MXS (S1/S0), (b) CASSCF MXS (S2/S1), and (c) MR-CISD MXS (S3/S2). The arrows are not to scale between different pictures.

Mentions: The g- andh-vectors characterizing the conical intersection50,52,62,63 are shownin Figures 7 and 8 forthe five computed MXS structures. The g-vector is defined by the energygradient difference between the two states, and the h-vector is thenonadiabatic coupling vector. A molecular deformation along thesevectors determines the branching space, lifts the degeneracy of thestates, and describes possible reaction coordinates.


A multireference configuration interaction study of the photodynamics of nitroethylene.

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

Computed g- and h-vectorsof the conical intersections found. (a)MR-CISD MXS (S1/S0), (b) CASSCF MXS (S2/S1), and (c) MR-CISD MXS (S3/S2). The arrows are not to scale between different pictures.
© Copyright Policy
Related In: Results  -  Collection

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

fig7: Computed g- and h-vectorsof the conical intersections found. (a)MR-CISD MXS (S1/S0), (b) CASSCF MXS (S2/S1), and (c) MR-CISD MXS (S3/S2). The arrows are not to scale between different pictures.
Mentions: The g- andh-vectors characterizing the conical intersection50,52,62,63 are shownin Figures 7 and 8 forthe five computed MXS structures. The g-vector is defined by the energygradient difference between the two states, and the h-vector is thenonadiabatic coupling vector. A molecular deformation along thesevectors determines the branching space, lifts the degeneracy of thestates, and describes possible reaction coordinates.

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