Issue 1, 1999

Photochemistry of the singlet oxygen [O2(1Δg)] sensitizer perinaphthenone (phenalenone) in N,N′-dimethylacetamide and 1,4-dioxane

Abstract

1H-Phenalen-1-one (perinaphthenone), an efficient singlet oxygen [O2(1Δg)] sensitizer with a quantum yield of singlet oxygen production (ΦΔ) close to unity, has been proposed as a universal standard for O2(1Δg) studies. However, data about the photochemical stability of phenalenone are limited to a few protic solvents. This parameter is of crucial interest for singlet oxygen studies under continuous irradiation over long periods of time. In this contribution, we present experimental results demonstrating that, despite low quantum yields, significant photochemical decomposition of phenalenone occurs under steady-state irradiation in air equilibrated 1,4-dioxane and N,N′-dimethylacetamide (DMA), mainly due to hydrogen abstraction from the solvent by its triplet excited state. Furthermore, singlet oxygen lifetime measurements as a function of irradiation time and comparison of the rates of decrease of the steady-state O2(1Δg) near-infrared (1270 nm) phosphorescence with those of phenalenone disappearance have led to the conclusion that at least one of the products formed during phenalenone irradiation contributes to singlet oxygen sensitization. Quantum yields of singlet oxygen production by phenalenone, determined using laser-induced optoacoustic calorimetry (LIOAC) and time-resolved near-infrared phosphorescence (TRPD), remain high in 1,4-dioxane and in DMA (0.99±0.05 and 0.87±0.05, respectively), confirming that this compound is a very efficient 1O2 sensitizer in a large variety of solvents (the ΦΔ value in DMA is the lowest measured so far).

Photochimie de la pe′rinaphte′none (phe′nale′none), un sensibilisateur de l'oxygène singulet [O2(1Δg)], dans le N , N ′-dime′thylace′tamide et le 1,4-dioxane. L'importance de la 1H-phe′nale′none-1 (ou pe′rinaphte′none) en tant que sensibilisateur de re′fe′rence pour la production d'oxygène singulet [O2(1Δg)] est alle′e croissante ces dernières anne′es. Cependant, la stabilite′ photochimique de ce compose′ a e′te′ seulement e′tudie′e dans un nombre limite′ de solvants protiques. Ce paramètre est d'une grande importance pour des e′tudes impliquant la production d'oxygène singulet sous irradiation prolonge′e du sensibilisateur. Dans cette contribution, nous pre′sentons des re′sultats montrant qu'une de′composition photochimique partielle de la phe′nale′none se produit sous irradiation en continue dans le 1,4-dioxane et dans le N,N′-dime′thylacetamide (DMA), principalement par suite de l'arrachement d'un atome d'hydrogène au solvant par l'e′tat excite′ triplet de la ce′tone. De plus, la de′termination des dure′es de vie de l'oxygène singulet en fonction du temps d'irradiation et la comparaison des vitesses de la de′croissance de la production d'oxygène singulet et de la disparition de la phe′nale′none nous ont conduit à la conclusion qu'au moins l'un des produits forme′s contribue à la production d'oxygène singulet. Nous avons de′termine′ les rendements quantiques de production d'oxygène singulet (ΦΔ) par la phe′nale′none en utilisant la combinaison de deux me′thodes diffe′rentes: la calorime′trie optoacoustique induite par impulsion laser et la de′tection de la phosphorescence de l'oxygène singulet dans le proche infrarouge (1270 nm). Les valeurs de ΦΔ dans le 1,4-dioxane (0.99±0.05) et dans le DMA (0.87±0.05) confirment que ce compose′ est un sensibilisateur de l'oxygène singulet très efficace dans une grande varie′te′ de solvants (la valeur dans le DMA est la plus faible mesure′e jusqu'à pre′sent).

Article information

Article type
Paper

New J. Chem., 1999,23, 85-93

Photochemistry of the singlet oxygen [O2(1Δg)] sensitizer perinaphthenone (phenalenone) in N,N′-dimethylacetamide and 1,4-dioxane

E. Oliveros, S. H. Bossmann, S. Nonell, C. Martí, G. Heit, G. Tröscher, A. Neuner, C. Martínez and A. M. Braun, New J. Chem., 1999, 23, 85 DOI: 10.1039/A804054K

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