title: Mechanism of activated chemiluminescence of cyclic peroxides: 1,2-dioxetanes and 1,2-dioxetanones.
abstract: Almost all chemiluminescent and bioluminescent reactions involve cyclic peroxides. The structure of the peroxide and reaction conditions determine the quantum efficiency of light emission. Oxidizable fluorophores, the so-called activators, react with 1,2-dioxetanones promoting the former to their first singlet excited state. This transformation is inefficient and does not occur with 1,2-dioxetanes; however, they have been used as models for the efficient firefly bioluminescence. In this work, we use the SA-CASSCF/CASPT2 method to investigate the activated chemiexcitation of the parent 1,2-dioxetane and 1,2-dioxetanone. Our findings suggest that ground state decomposition of the peroxide competes efficiently with the chemiexcitation pathway, in agreement with the available experimental data. The formation of non-emissive triplet excited species is proposed to explain the low emission efficiency of the activated decomposition of 1,2-dioxetanone. Chemiexcitation is rationalized considering a peroxide/activator supermolecule undergoing an electron-transfer reaction followed by internal conversion.
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo, Brazil. wjbaader@iq.usp.br and Department of Chemistry-Ångström, Uppsala Center for Computational Chemistry, UC3, Uppsala University, P.O. Box 518, SE-75120, Uppsala, Sweden. roland.lindh@kemi.uu.se.
authors.forename: Felipe A
authors.initials: FA
authors.lastname: Augusto
authors.affiliation: Department of Chemistry-Ångström, Uppsala Center for Computational Chemistry, UC3, Uppsala University, P.O. Box 518, SE-75120, Uppsala, Sweden. roland.lindh@kemi.uu.se and Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, 46071, València, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Francés-Monerris
authors.affiliation: Department of Chemistry-Ångström, Uppsala Center for Computational Chemistry, UC3, Uppsala University, P.O. Box 518, SE-75120, Uppsala, Sweden. roland.lindh@kemi.uu.se.
authors.forename: Ignacio
authors.identifier: http://orcid.org/0000-0002-0684-7689
authors.initials: I
authors.lastname: Fdez Galván
authors.affiliation: Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, 46071, València, Spain.
authors.forename: Daniel
authors.identifier: http://orcid.org/0000-0001-6495-2770
authors.initials: D
authors.lastname: Roca-Sanjuán
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo, Brazil. wjbaader@iq.usp.br.
authors.forename: Erick L
authors.initials: EL
authors.lastname: Bastos
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000, São Paulo, Brazil. wjbaader@iq.usp.br.
authors.forename: Wilhelm J
authors.identifier: http://orcid.org/0000-0001-7678-8576
authors.initials: WJ
authors.lastname: Baader
authors.affiliation: Department of Chemistry-Ångström, Uppsala Center for Computational Chemistry, UC3, Uppsala University, P.O. Box 518, SE-75120, Uppsala, Sweden. roland.lindh@kemi.uu.se.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh