Analyse de quelques processus photophysiques chez les dérivés diphénylés en position 4 du γ-pyranne et du γ-thiopyranne

Abstract

The photophysical processes along with the photolysis of 4,4-diphenyl-γ-pyran (1) and 4,4-diphenyl-γ-thiopyran (2) are discussed in this paper. The solvent effect, the temperature effect, and the photolytic source intensity dependence of the yield of the secondary photoproduct are all among the experimental parameters investigated. It is shown that the first singlet–singlet electronic transition in molecules 1 and 2 is ππ*. in nature. The divinyl ether and divinyl thioether chromophore play a role in this transition and also directly contribute to the radiationless deactivation of the first excited singlet states of these molecules. On the other hand the energy of the first triplet ππ* state seems to be more localized in the phenyl groups of the molecules 1 and 2.It is also shown that the photolysis of molecule 1 occurs by a monomolecular mechanism to produce a photoaldehyde which is also photolysed under prolonged irradiation. This aldehyde has also been shown to be a secondary photoproduct in the photoreaction sequence of 4,4-diphenyl-γ-pyran.