Experimental Evidence of the Occurrence of Intramolecular Electron Transfer in Catalyzed 1,2-Dioxetane Decomposition

The activation parameters for the thermal decomposition of 13 acridinium-substituted 1,2-dioxetanes, bearing an aromatic moiety, were determined and their chemiluminescence emission quantum yields estimated, utilizing in situ photosensitized 1,2-dioxetane generation and observation of its thermal decomposition kinetics, without isolation of these highly unstable cyclic peroxides. Decomposition rate constants show linear free-energy correlation for electron-withdrawing substituents, with a Hammett reaction constant of rho = 1.3 +/- 0.1, indicating the occurrence of an intramolecular electron transfer from the acridinium moiety to the 1,2-dioxetane ring, as postulated by the intramolecular chemically initiated electron exchange luminescence (CIEEL) mechanism. Emission quantum yield behavior can also be rationalized on the basis of the intramolecular CIEEL mechanism, additionally evidencing its occurrence in this transformation. Both relations constitute the first experimental evidence for the occurrence of the postulated intramolecular electron transfer in the catalyzed and induced decomposition of properly substituted 1,2-dioxetanes.

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2005/58320-4]

Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF)

Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF)

Deutscher Akademischer Austauschdienst (DAAD)

Deutscher Akademischer Austauschdienst (DAAD)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Coordenadoria de Aperfeicoamento de Pessoal de Ensino Superior (CAPES)[BEX 1132/04-0]