The photostability and fluorescence properties of diphenylisobenzofuran

The photostability and fluorescence properties of 1,3-diphenylisobenzofuran (DPBF), a popular singlet oxygen (1O2 or 1Δg) trapping-agent used in various solvents, are examined by UV–vis absorption, steady-state and time-resolved fluorescence techniques, as well as laser flash photolysis. DPBF is found to be easily photolyzed even if it is only exposed to the weak daylight in halogen-containing solvents in the absence of singlet oxygen. The photolysis is due to the addition of •CCl3 (•CHCl2) to DPBF in the absence of oxygen, or •OOCCl3 (•OOCHCl2) initiated chain polymerization of DPBF in the presence of oxygen. This result suggests that the reported singlet oxygen production in these solvents detected by DPBF was significantly higher than the true value. DPBF in DMF, DMSO, etc., on the other hand, is stable enough to enable fluorescence measurements. The fluorescence quantum yield of DPBF is very high in aprotic solvents and close to unity. The absorption, excitation and emission maxima are only slightly affected by the nature of solvents. The fluorescence lifetime is 5.0±0.3 ns.