Photochemical Properties of Excited Triplet State of 6H-Purine-6-thione Investigated by Laser Flash Photolysis

1998 ◽  
Vol 102 (8) ◽  
pp. 1338-1344 ◽  
Author(s):  
Maksudul M. Alam ◽  
Mamoru Fujitsuka ◽  
Akira Watanabe ◽  
Osamu Ito
Keyword(s):  
Triplet State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Excited Triplet State ◽  
Excited Triplet ◽  
Photochemical Properties

The Excited Triplet State Properties of Titanyl Phthalocyanine and its Sulfonated Derivatives

2010 ◽  
Vol 63 (10) ◽  
pp. 1471 ◽  
Author(s):  
Xian-Fu Zhang ◽  
Jingyao Huang ◽  
Qian Xi ◽  
Yun Wang
Keyword(s):  
Aqueous Solution ◽  
Quantum Yield ◽  
Triplet State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Zinc Phthalocyanine ◽  
Excited Triplet State ◽  
Nanosecond Laser ◽  
Excited Triplet ◽  
Titanyl Phthalocyanine

Titanyl phthalocyanine (TiOPc) is a well-known, excellent photoconductive material for laser printers and photocopying machines. Its organic derivatives have recently been shown to be excellent photosensitizers for singlet oxygen [O2(1Δg)] production. The excited triplet state properties of TiOPc, in homogeneous DMSO solution, were measured in this study for the first time by nanosecond laser flash photolysis. The data enabled comparisons to be drawn with TiOPcS4 and zinc phthalocyanine (ZnPc), ultimately providing a better understanding of the reported observations. Absorption, fluorescence, and O2(1Δg) sensitization were also studied. TiOPcS4 in DMSO shows remarkably different fluorescence properties from that reported in aqueous solution: both the fluorescence quantum yield (Φf = 0.068) and the fluorescence lifetime (τf = 3.71 ns) were much larger than that reported for aqueous solutions (0.012 and 0.09 ns, respectively). The photosensitizing properties of TiOPcS4 in DMSO are also so significantly better than that in aqueous solution, i.e. triplet lifetime (τT) of 252 μs, triplet quantum yield (ΦT) of 0.42, and the quantum yield of O2(1Δg) (ΦΔ) of 0.49; compare with values of 60 μs, 0.32, 0.13 reported in aqueous solution. TiOPc, however, shows comparable photophysical properties to that of ZnPc, a well-recognized photosensitizer. These results suggest that TiOPc and its derivatives are not only good photoconductors but also good photosensitizers of O2(1Δg), which may find application in photodynamic therapies for treatment of cancer.

Efficient photodecarboxylation of 3- and 4-acetylphenylacetic acids in aqueous solution

2004 ◽  
Vol 82 (12) ◽  
pp. 1760-1768 ◽  
Author(s):  
Lawrence A Huck ◽  
Musheng Xu ◽  
Kaya Forest ◽  
Peter Wan
Keyword(s):  
Aqueous Solution ◽  
Triplet State ◽  
Benzene Ring ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Excited Triplet ◽  
Acetophenone Derivatives ◽  
Acetyl Group ◽  
Electron Withdrawing Group

The photochemistry of 3- and 4-acetylphenylacetic acids (6 and 7) has been studied in aqueous solution. This work is a continuation of research efforts aimed at understanding the structural effects on the efficacy for benzyl carbanion photogeneration via photodecarboxylation. The nitro group (at the 3- and 4-positions) is known to be an exceptionally good activating group on the benzene ring — because of its enhanced electron-withdrawing effect in the excited triplet state — for photodecarboxylation and the related photo-retro-aldol type process. It is shown in this work that the acetyl group is an equally good activating group for the photodecarboxylation. Thus, the photochemistry of 6 and 7 parallels much of what was observed for the corresponding nitrophenylacetic acids 1 and 2. Both 6 and 7 photodecarboxylate efficiently (Φd = 0.60 and 0.22, respectively, at pH 7) via the carboxylate form, to give observable (by laser flash photolysis) benzyl carbanion or related intermediates. The meta isomer 6 displays an acid-catalyzed pathway for photodecarboxylation at pH < 3 and along with its enhanced overall reactivity, is consistent with a meta effect of the acetyl group. Triplet state reactivity is inferred from sensitization and laser flash photolysis experiments. Based on the results of this work, the acetyl group may now be viewed as an "enhanced" electron-withdrawing group (in the excited state) when attached to a benzene ring (i.e., in acetophenone derivatives) that is capable of inducing ionic reactions, which is not the traditional photochemistry that is expected from such compounds.Key words: photodecarboxylation, acid catalysis, acetophenone, photogenerated carbanion, enol, enolate.

Effect of Aggregation on Bacteriochlorin a Triplet-state Formation: A Laser Flash Photolysis Study¶

2002 ◽  
Vol 76 (5) ◽  
pp. 480 ◽  
Author(s):  
Xavier Damoiseau ◽  
Francis Tfibel ◽  
Maryse Hoebeke ◽  
Marie-Pierre Fontaine-Aupart
Keyword(s):  
Triplet State ◽  
State Formation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

Triplet state quenching of phenosafranine dye by indolic compounds studied by transient absorption spectroscopy

2015 ◽  
Vol 14 (2) ◽  
pp. 407-413 ◽  
Author(s):  
Martín F. Broglia ◽  
Carlos M. Previtali ◽  
Sonia G. Bertolotti
Keyword(s):  
Triplet State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Transient Absorption Spectroscopy ◽  
Synthetic Dye ◽  
Biological Relevance ◽  
Indolic Compounds

The interaction of the triplet state of the synthetic dye phenosafranine (3,7-diamino-5-phenylphenazinium chloride) with indolic compounds of biological relevance was investigated in water by means of laser flash photolysis.

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