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Soto-Martín, Juan Otero-Fernández-de-Molina, Juan Carlos Ávila-Ferrer, Francisco José Peláez, Daniel 2025-01-30T11:27:54Z 2025-01-30T11:27:54Z 2019-01-04 https://hdl.handle.net/10630/37391 10.1039/c8cp06974c 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. eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Azidas Conical Intersections and Intersystem Crossings Explain Product Formation in Photochemical Reactions of Aryl Azides journal article