1H-INDENYLFURAN AND THIOPHENE DERIVATIVES– A NEW CLASS OF SINGLET OXYGEN SENSITIZERS

Abstract— Photophysical and photochemical properties of 1H-indenylfuran and thiophene derivatives were studied. UV spectra showed that all the compounds tested absorbed UV light in the region 350–380 nm. The fluorescence spectra of 4a-e showed bands in the region 410–470 nm and quantum yields (φ_F) in the range 0.25–0.88. Attempts to calculate the triplet energy of 4a-e failed except for 4c and 4d , which showed E_T= 43–44 kcal mol^-1. These compounds are a new class of singlet oxygen sensitizers. The sensitized reaction of 2,5-dimethylfuran with singlet oxygen was followed showing that 4a and 4e are more reactive than α-terthiophene (4.0 and 2.5 times respectively), while the other compounds show the same reactivity as 1 . This behavior can be explained considering the different intersystem crossing quantum yields of compounds 4a-e . Diazabicyclo2. 2. 2]octane is a quencher of singlet oxygen in this reaction, while we can exclude superoxide ion formation using the photooxidation of α, α-dimethylstilbene.