title: Solvent viscosity influence on the chemiexcitation efficiency of inter and intramolecular chemiluminescence systems.
abstract: The effects of the medium viscosity on the chemiexcitation quantum yields of the induced decomposition of 1,2-dioxetanes (highly efficient intramolecular CIEEL system) and the catalyzed decomposition of diphenoyl peroxide and a 1,2-dioxetanone derivative (model systems for the intermolecular CIEEL mechanism, despite their low efficiency) are compared in this work. Quantum yields of the rubrene catalyzed decomposition of diphenoyl peroxide and spiro-adamantyl-1,2-dioxetanone as well as the fluoride induced decomposition of a phenoxy-substituted 1,2-dioxetane derivative are shown to depend on the composition of the binary solvent mixture toluene/diphenyl ether, which possess similar polarity parameters but different viscosities. Correlations of the quantum yield data with the medium viscosity using the diffusional and the frictional (free-volume) models indicate that the induced 1,2-dioxetane decomposition indeed occurs by an entirely intramolecular process and the low efficiency of the intermolecular chemiluminescence systems (catalyzed decomposition of diphenoyl peroxide and 1,2-dioxetanone derivative) is not primarily due to the cage escape of radical ion species.
authors.affiliation: Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil. wjbaader@iq.usp.br.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Khalid
authors.forename: Sergio P
authors.initials: SP
authors.lastname: Souza
authors.forename: Luiz F M L
authors.initials: LF
authors.lastname: Ciscato
authors.forename: Fernando H
authors.initials: FH
authors.lastname: Bartoloni
authors.forename: Wilhelm J
authors.initials: WJ
authors.lastname: Baader