• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.63-67
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• 2001

The photophysical properties and the singlet oxygen generation efficiency of tetrathiarubyrin have been investigated to elucidate the possibility of its use as a photodynamic therapy (PDT) photosensitizer by steady-state and time-resolved spectroscopic methods. The observed photophysical properties were affected by various molecular aspects, such as extended ${\pi}conjugation$, structural distortion, and internal heavy atom. The steady-state electronic absorption spectrum was red-shifted due to the extended $\pi-conjugation$, and the spin orbital coupling was enhanced by the structural distortion and the internal heavy atom effect. As a result of the enhanced spin orbital coupling, the triplet quantum yield increased to 0.90 $\pm$ 0.10 and the triplet state lifetime was shortened to 7.0 $\pm$ 1.2 ${\mu}s$. Since the triplet state decays at a relatively faster rate, the efficiency of the oxygen quenching of the triplet state decreases. The singlet oxygen quantum yield was estimated to be 0.52 $\pm$ 0.02, which is somewhat lower than expected. On the other hand, the efficiency of singlet oxygen generation during the oxygen quenching of triplet state, $f{\Delta}^T$, is near unity. Such high efficiency of singlet oxygen generation can be explained by the following two possible factors: The hydrogen bonding of ethanol which impedes the deactivation pathway of the charge transfer complex with oxygen to the ground state, the less probability of the aggregation formation.

• Journal of Photoscience
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• v.3 no.3
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• pp.141-145
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• 1996

The heat generated by nonradiative decay dynamics induces thermal lens effect. From such an effect, photodynamic properties of solutions can be investigated with two-color pulsed thermal lens experiments which have the time resolution of down to nanoseconds. In this study, using nanosecond two-color thermal lens method, we investigated the triplet state of benzophenone and the singlet oxygen state dynamics in various oxygen concentration solvents. The measured triplet state lifetimes, singlet oxygen relaxation times and singlet oxygen formation quantum yields are in good agreement with the reference values. From these parameters the existence of the triplet exciplex formation between benzophenone and benzene is proved, and it is also suggested that the relaxations of triplet states of benzophenone undergo coupled dynamics with some of singlet oxygens in oxygen-rich conditions.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.281-285
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• 2002

The photophysical properties and the singlet oxygen generation efficiencies of meso-tetraphenyl-trithiasapphyrin $(S_3TPS)$ and meso-tetmkis(p-methoxy phenyl)-trithiasapphy rin ((p-MeO)-$S_3TPS$) have been investigated, utilizing steady-state and time-resolved spectroscopic methods to elucidate the possibility of their use as photosensitizers for photodynamic therapy (PDT). The observed photophysical properties were compared with those of other porphyrin-like photosensitizers in geometrical and electronic structural aspects, such as extended ${\pi}$ conjugation, structural distortion, and internal heavy atoms. The steady-state electronic absorption and fluorescence spectra were both red-shifted due to the extended ${\pi}$-conjugation. The fluorescence quantum yields were measured as very small. Even though intersystem crossing rates were expected to increase due to the increment of spin orbital coupling, the triplet quantum yields were measured as less than 0.15. Such characteristics can be ascribed to the more enhanced internal conversion rates compared with the intersystem crossing rates. Furthermore, the triplet state lifetimes were shortened to -1.0 ${\mu}s$ as expected. Therefore, the singlet oxygen quantum yields were estimated to be near zero due to the fast triplet state decay rates and the inefficient energy transfer to the oxygen molecule as well as the low triplet quantum yields. The low efficiencies of energy transfer to the oxygen molecule can be attributed to the lower oxidation potential and/or the energetically low lying triplet state. Such photophysical factors should be carefully evaluated as potential photosensitizers that have extended ${\pi}$-conjugation and heavy core atoms synthesized for red-shifted absorption and high triplet state quantum yields.

• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.72-75
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• 2013

Bulk nanobubble is one of the nanoscopic gaseous state found in the solution. We measured transient absorption spectra of eosin Y in the excited triplet state ($^3EY^{2-*}$) to elucidate differences in the dissipation process of the bulk nanobubble of oxygen molecule at air pressure. The time dependence of the oxygen dissipation process was classified three time domains (P1, P2 and P3). The comparison of ordinary bubbling method gave different results at P3 in contrast to similar results at P1 and P2, indicating the existence of characteristic dissolving state in the case of nanobubble.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1149-1151
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• 2000

• Bulletin of the Korean Chemical Society
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• v.13 no.2
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• pp.166-172
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• 1992

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethoxyalkyl)phthalimides(alkyl=E thyl, n-propyl, n-butyl, n-pentyl, and n-octyl). Photocyclizations occur in methanol in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from oxygen in the $\alpha-silylmethoxy$ groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate $\alpha-silylmethoxy$ cation radicals and cyclization by radical coupling are proposed. In contrast, photoreaction of N-(trimethylsilylmethoxyethyl) phthalimide in acetone follows different reaction routes to produce two cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon $\alpha$ to silicon and oxygen atoms via triplet carbonyl hydrogen abstraction triplet carbonyl silyl group abstraction pathways. The normal singlet SET pathway dominates these triplet processes for photoreaction of this substance in methanol. The efficient and regioselective cyclization reactions observed for photolysis in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.10b
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• pp.106-106
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• 2003

Many polycyclic aromatic hydrocarbons (PAH) are acutely toxic to fish and other aquatic organisms in the presence of environmentally realistic intensities of solar ultraviolet radiation (SUVR). The phototoxicity of polycyclic aromatic hydrocarbons (PAHs) occurs through photodynamic activation of PAH compounds. Oxygen molecules react as quenchers with excited triplet states of PAHs producing reactive oxygen species (ROS).(omitted)

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1256-1260
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• 2007

Two β-diketone derivatives bearing triphenylene (1-naphthalene-2-yl-3-triphenylen-2-yl-propane-1,3-dione (NTPD)) and naphthalene (1,3-di-naphthalene-2-yl-propane-1,3-dione (DNPD)) and their Ln(III) complexes (Ln = Er or Gd) were synthesized and their photophysical properties were investigated. The sensitized emission of Er3+ ion in Er3+-[NTPD]3(terpy) and Er3+-[DNPD]3(terpy) was observed upon excitation at absorption maximum of ligands. Their photophysical studies indicate the sensitization of Er3+ luminescence by energy transfer through the excited triplet state of β-diketone ligand. The energy transfer rate through the excited triplet state of β-diketone ligand to Er3+ ion occurs faster than that of the oxygen quenching rate.

• YAKHAK HOEJI
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• v.44 no.1
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• pp.36-40
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• 2000

The photodegradation of pefloxacin, photolabile fluoroquinolone antibacterial agent, was studied. In the presence of $N_2$, photodegradation of pefloxacin was suppressed. The singlet oxygen and free radical generated in the reaction media proceeded photochemical reaction. The photodegradation of peflxacin was sensitized by benzophenone, a triplet state sensitizer.

• Journal of Photoscience
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• v.9 no.2
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• pp.515-517
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• 2002

Photodynamic therapy (PDT) is a cancer treatment modality which utilizes the cytotoxicity of the active singlet oxygen derived from irradiation of a tumor accumulated photosensitizer. As the oxygen in the singlet state radiates an emission of 1270nm wavelength when it decays to the triplet state, detection of the emission helps us to understand the mechanism of PDT or to evaluate photosensitizers. We detected the 1270nm emission from photosensitizers Photofrin and ATX-SI0 in vitro and in vivo by means of high sensitive NIR detectors. We obtained the maximum amount of singlet oxygen at irradiation wavelength of 665-670nm from a HeLa tumor in a nude mouse which is injected with ATX-S10.