Giussani, A;
Worth, GA;
(2017)
Insights into the Complex Photophysics and Photochemistry of the Simplest Nitroaromatic Compound: A CASPT2//CASSCF Study on Nitrobenzene.
Journal of Chemical Theory and Computation
, 13
(6)
pp. 2777-2788.
10.1021/acs.jctc.6b01149.
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Abstract
Nitrobenzene is the simplest nitroaromatic compound and yet is characterized by a challenging and rich photophysics and photochemistry. In the present contribution, the main decay paths undertaken by the system after UV absorption from both the brightest 1(Laππ*) and the lowest 1(nAπ*) singlet excited states have been characterized by means of CASPT2//CASSCF computations. The obtained results match with the main photophysical properties experimentally reported: the lack of fluorescence and phosphorescence emission is justified by the presence of accessible conical intersections and intersystem crossing regions between, respectively, the 1(nAπ*) and 3(nAπ*) states and the ground state, while the high triplet quantum yield is attributable to the strong coupling between the 1(nAπ*) and 3(πOπ*) states along the main decay path of the former. Two not previously reported singlet–triplet crossing regions, termed (T1/S0)stc-NO and (T1/S0)stc-ep, have been here documented, from which the ground state can decay toward NO and phenoxy radical production and toward the formation of an epoxide ring structure, respectively. A possible mechanism leading to the photoisomerization of the nitro into the nitrite group, believed to be a key step in the photodegradation of nitrobenzene, has been proposed, based on the geometrical deformation recorded along the decay path leading from the 1(nAπ*) state back to the original ground state through a conical intersection characterized by a significant shortening of the carbon–nitrogen bond.
| Type: | Article |
|---|---|
| Title: | Insights into the Complex Photophysics and Photochemistry of the Simplest Nitroaromatic Compound: A CASPT2//CASSCF Study on Nitrobenzene |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1021/acs.jctc.6b01149 |
| Publisher version: | http://dx.doi.org/10.1021/acs.jctc.6b01149 |
| Language: | English |
| Additional information: | This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html), which permits copying and redistribution of the article or any adaptations for non-commercial purposes. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/1565039 |
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