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The balance between charge transfer and non-charge transfer pathways in the sensitization of singlet oxygen by ππ* triplet states

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Abstract

A charge transfer (CT) channel and a non-CT deactivation channel, both leading to formation of O2(1Σg+), O2(1Δg) and O2(3Σg−), compete in the quenching of triplet states by O2. Recent studies by our group demonstrated that these channels are described by rather simple and general quantitative relations. In the present paper we use the detailed kinetic data on the quenching by O2 of ππ* triplet sensitizers of three homologous aromatic series in CCl4 to derive a parameter, which describes the balance between CT and non-CT deactivation. This quantity, pCT, is the relative contribution of CT mediated deactivation and is easily calculated for a sensitizer of known triplet energy from its quenching rate constant. The parameter pCT quantitatively describes the balance between both deactivation channels without requiring any knowledge of oxidation potentials. It is shown how the variation of pCT influences the efficiencies and the rate constants of O2(1Σg+), O2(1Δg) and O2(3Σg−) formation in the quenching process.

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  1. Institut für Physikalische und Theoretische Chemie, Johann Wolfgang Goethe-Universität, Marie-Curie-Straße 11, D60439, Frankfurt am Main, Germany

    Reinhard Schmidt

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Schmidt, R. The balance between charge transfer and non-charge transfer pathways in the sensitization of singlet oxygen by ππ* triplet states. Photochem Photobiol Sci 4, 481–486 (2005). https://doi.org/10.1039/b502735g

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