2026-05-30T02:49:27Zhttps://riuma.uma.es/rest/oai/request

oai:riuma.uma.es:10630/373912026-02-03T11:31:49Zcom_10630_2254col_10630_37953

Conical Intersections and Intersystem Crossings Explain Product Formation in Photochemical Reactions of Aryl Azides Soto-Martín, Juan Otero-Fernández-de-Molina, Juan Carlos Ávila-Ferrer, Francisco José Peláez, Daniel Azidas Photochemistry of 3- and 4-methoxyphenyl azide at 266 nm has been studied by means of the complete active space self-consistent field (CASSCF) and multi-configurational second-order perturbation (MS-CASPT2) methods. Minima and interstate crossing points have been optimized with the CASSCF method. The calculations predict that the key step of the photolysis of both azides is a non-radiative process. However, an important difference is found when we compare the reactivity of both isomers of azide, deactivation of 3-methoxyphenyl azide (1) can occur via two reaction channels (internal conversion or intersystem crossing), which lead to formation of the dimer of 2H-azepine derivative (2a) and 3,3'-dimethoxyazobenzene (2b). In contrast, deactivation of 4-methoxyphenyl azide (3) takes place via a singlet to triplet intersystem crossing, which leads to formation of 4,4'-dimethoxyazobenzene (4). After initial deactivation, both isomers follow a cascade of surface crossings until to reach the final nitrenes, respectively. The reference active space for the two azides is 14 electrons in 13 orbitals and comprises the six -type orbitals of the aromatic ring plus four -(N-N2) and five -type orbitals of the -N3 moiety. 2025-01-30T11:27:54Z 2025-01-30T11:27:54Z 2019-01-04 journal article https://hdl.handle.net/10630/37391 10.1039/c8cp06974c eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional