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The fluorescence lifetime (τf), emission quantum yield (Φf), absorption and emission spectral data of 20 fluorescein derivatives were measured under the same conditions by using time-correlated single photon counting, steady state fluorescence and absorption methods to get comparable data. Based on the results, the factors and mechanism that control the fluorescence properties of the fluorescein dyes are discussed. Both Φf and τf are remarkably dependent on the substitution on either xanthene or phenyl rings, but their ratio (Φf/τf), i.e. rate constant of radiation process, is a constant value (0.20 × 10(9) s(-1)). The rate constant of nonradiation process, on the other hand, is varied with both the structure and the solvent used.

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The excited triplet-, singlet-, and ground-state properties as well as singlet oxygen generation capability of four brominated BODIPY dyes were measured in toluene with laser flash photolysis, fluorescence spectroscopy, time-correlated single-photon counting, and absorption spectroscopy. The triplet-triplet (T1-Tn) absorption spectra were identified for four dyes 1B, 2B, 4B, and 6B substituted with one, two, four, and six Br atoms, respectively. The triplet quantum yield (ΦT) of a usual BODIPY dye is negligible and has rarely been studied. So is the case for the parent compound 0B (8-phenyl boron-dipyrromethene), in which no Br atom is present. The substitution of the first Br atom into the π ring of BODIPY allowed a dramatic increase of ΦT from 0.0 of 0B to 0.39 for 1B. The further addition of Br number increased ΦT to 0.46, 0.50, and 0.66 for 2B, 4B, and 6B, respectively. The triplet lifetimes τT are also fairly long, which is 43, 39, 36, and 26 μs, for 1B, 2B, 4B, and 6B, respectively. The brominated BODIPY dyes are therefore efficient singlet oxygen photosensitizers with the formation quantum yield of 0.39, 0.45, 0.49, and 0.64 for 1B, 2B, 4B, and 6B, respectively. The result indicates their potential application in photodynamic therapy of cancer. The fluorescence properties of the dyes were also measured.

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UV/vis absorption and fluorescence spectra and fluorescence quantum yields and lifetimes of a series of methano-and pyrrolidino-[60]fullerene derivatives in different solvents are studied systematically. The absorption and fluorescence properties of the derivatives with different substituents are somewhat different from those of [60]fullerene, but very similar among themselves, indicating that the low-lying transitions and the photoexcited state processes are dictated by the electronic structures of functionalized [60]fullerene cages. The results also allow an examination of the issue concerning discrepancies between experimentally determined transition probabilities and those calculated in terms of the Strickler-Berg equation for fullerene molecules. In addition, quenchings of the excited singlet states of the [60]fullerene derivatives by electron donor N,Ndiethylaniline (DEA) and the formation of emissive fullerene-DEA exciplexes in solvents of different polarities are investigated.