Speaker: Angelo Giussani, University of Valencia
Program Description:
Nitrobenzene is characterized by a reach photophysics and photochemistry: it is supposed to decay on a fs timescale from the singlet to the triplet manifold, challenging the generally accepted vision of much slower singlet-to-triplet decays in purely organic molecules;1 it photodegradates to three different photoproducts, NO2, NO and O;2 it photoreleases NO accordingly to two mechanisms, one leading to NO molecules with high translational and rotational energy (associated with a dissociation on the triplet manifold), the other forming NO with low translational and rotational energy (related to a possible roaming mechanism).3,4
Due to its relatively small molecular size, high level ab initio electronic structure calculations are computationally affordable, making nitrobenzene an ideal candidate for deepening our understanding of photophysical/photochemical phenomena and putting at comparison computational models with experimental evidences (and vice versa).5-7
[1] S. W. Crane, M. Garrow, P. D. Lane, K. Robertson, A. Waugh, J. M. Woolley, V. G. Stavros, M. J. Paterson, S. J. Greaves, and D. Townsend, "The Value of Different Experimental Observables: A Transient Absorption Study of the Ultraviolet Excitation Dynamics Operating in Nitrobenzene" J. Phys. Chem. A 127, 6425–6436 (2023).
[2] D. B. Galloway, J. A. Bartz, L. G. Huey, and F. F. Crim, F. F. "Pathways and Kinetic Energy Disposal in the Photodissociation of Nitrobenzene" J. Chem. Phys. 98, 2107-2114 (1993).
[3] M. L. Hause, N. Herath, R. Zhu, M. C. Lin, and A. G. Suits, “Roaming-mediated isomerization in the photodissociation of nitrobenzene” Nat. Chem. 3, 932–937 (2011).
[4] N. B. Bejoy, P. R. Chowdhury, and G. N. Patwari, “Modulating the Roaming Dynamics for the NO Release in ortho-Nitrobenzenes” J. Phys. Chem. Lett. 14, 2816-2822 (2023).
[5] A. Giussani and G. A. Worth, “Insights into the complex photophysics and photochemistry of the simplest nitroaromatic compound: A CASPT2//CASSCF study on nitrobenzene” J. Chem. Theory Comput. 13, 2777–2788 (2017).
[6] A. Giussani and G. A. Worth, “How important is roaming in the photodegradation of nitrobenzene?” Phys. Chem. Chem. Phys. 22, 15945–15952 (2020).
[7] A. Giussani and G. A. Worth, “On the photorelease of nitric oxide by nitrobenzene derivatives: A CASPT2//CASSCF model” J. Chem. Phys. 157, 204301 (2022).
