title: Can the Closed-Shell DFT Methods Describe the Thermolysis of 1,2-Dioxetanone?
abstract: The chemiluminescent decomposition of 1,2-dioxetanone has in the past been studied by state-of-the-art multireference quantum chemical calculations, and a stepwise biradical mechanism was established. Recently, this decomposition has been reinvestigated, and a concerted mechanism has been proposed based on calculations performed at the closed-shell density functional theory (DFT) level of theory. In order to solve this apparent mechanistic contradiction, the present paper presents restricted and unrestricted DFT results obtained using functionals including different amounts of Hartree-Fock (HF) exchange, repeating and complementing the above-mentioned DFT calculations. The calculated results clearly indicate that the closed-shell DFT methods cannot correctly describe the thermolysis of 1,2-dioxetanone. It is found that unrestricted Kohn-Sham reaction energies and barriers are always lower than the ones obtained using a restricted formalism. Hence, from energy principles, the biradical mechanism is found to be prevailing in the understanding of the 1,2-dioxetanone thermolysis.
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Yue
authors.affiliation: Department of Chemistry-Ångström, The Theoretical Chemistry Programme, Uppsala University, P.O. Box 518, S-75120 Uppsala, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Roca-Sanjuán
authors.affiliation: Department of Chemistry-Ångström, The Theoretical Chemistry Programme, Uppsala University, P.O. Box 518, S-75120 Uppsala, Sweden.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh
authors.affiliation: Université d'Aix-Marseille, Institut de Chimie Radicalaire, 13397 Marseille Cedex 20, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Liu