Flash Photolysis and ESR Studies on Hematoporphyrin and Photofrin II in Polar and Microheterogeneous Environment

1989 ◽  
Vol 44 (4) ◽  
pp. 283-290 ◽  
Author(s):  
Raimund Quint ◽  
Ruth Maria Quint ◽  
Nikola Getoff ◽  
Tsvetan Gantchev ◽  
Maria Shopova
Keyword(s):  
Triplet State ◽  
Singlet Oxygen ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Reducing Agent ◽  
Photodynamic Treatment ◽  
Photofrin Ii

Hematoporphyrin (HP) and its derivatives (HPD; e.g. photofrin II) are used as efficient sensitizers in the photodynamic treatment of tumors. The photoinduced formation of various transients resulting from these substrates at pH 12 and 7.4 were studied by conventional flash photolysis and by ESR techniques in the presence of various additives. EDTA is acting as an efficient reducing agent for the triplet state of the substrates. The absorption spectra of some transients (HP·-, HP -OH, HPD·-, HPD -OH) were obtained. Further, ESR studies (pH 4-7) showed that 3HP is mostly converted into HP·- - in the presence of EDTA, but this is not the case with 3HPD. In airfree HPD solutions a longlived transient was registered, which was attributed to HPD·+ species. In aerated substrate solutions the singlet oxygen ( 1O2) and peroxyradicals are formed. The discussed transients very likely are involved in the photodynamic treatment of tumors in man.

scholarly journals Effective Singlet Oxygen Sensitizers Based on the Phenazine Skeleton as Efficient Light Absorbers in Dye Photoinitiating Systems for Radical Polymerization of Acrylates

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3085
Author(s):  
Ilona Pyszka ◽  
Zdzisław Kucybała ◽  
Beata Jędrzejewska
Keyword(s):  
Quantum Yield ◽  
Visible Light ◽  
Triplet State ◽  
Singlet Oxygen ◽  
Radical Polymerization ◽  
State Formation ◽  
Flash Photolysis ◽  
Comparative Method ◽  
Aromatic Rings ◽  
Light Absorbers

A series of dyes based on the phenazine skeleton were synthesized. They differed in the number of conjugated double bonds, the arrangement of aromatic rings (linear and/or angular system), as well as the number and position of nitrogen atoms in the molecule. These compounds were investigated as potential singlet oxygen sensitizers and visible light absorbers in dye photoinitiating systems for radical polymerization. The quantum yield of the singlet oxygen formation was determined by the comparative method based on the 1H NMR spectra recorded for the tested dyes in the presence of 2,3-diphenyl-p-dioxene before and after irradiation. The quantum yield of the triplet state formation was estimated based on the transient absorption spectra recorded using the nanosecond flash photolysis technique. The effectiveness of the dye photoinitiating system was characterized by the initial rate of trimethylolpropane triacrylate (TMPTA) polymerization. In the investigated photoinitiating systems, the sensitizer was an electron acceptor, whereas the co-initiator was an electron donor. The effectiveness of TMPTA photoinitiated polymerization clearly depended on the arrangement of aromatic rings and the number of nitrogen atoms in the modified phenazine structure as well as the quantum yield of the triplet state formation of the photosensitizer in the visible light region.

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

Absorption Spectra of Substituted 2-Phenylindan-1,3-Dion-2-YL Radicals in Solution

1983 ◽  
Vol 38 (12) ◽  
pp. 1337-1341
Author(s):  
J. Zechner ◽  
N. Getoff ◽  
I. Timtcheva ◽  
F. Fratev ◽  
St. Minchef
Keyword(s):  
Free Energy ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Bathochromic Shift ◽  
Substitution Effects ◽  
Linear Free Energy Relationship ◽  
Linear Free Energy

Abstract Flash photolysis of a series of 2-phenylindandione-1,3 derivatives substituted in the 4′ position results in both the formation of stable benzylidenephthalides and of phenylindan-1,3-dion-2-yl radicals. The u. v. absorption maxima of these radicals are dependent on the solvent and show a bathochromic shift upon substitution. These substitution effects were correlated by means of a linear free energy relationship. Attempts were made to draw conclusions concerning the changes in the gap of the states involved and their curvature due to substitution.

Laser-flash-photolysis study of aliphatic thioketone triplets. Self-quenching and singlet-oxygen sensitization

1985 ◽  
Vol 81 (9) ◽  
pp. 1383 ◽  
Author(s):  
Kankan Bhattacharyya ◽  
Challa V. Kumar ◽  
Paritosh K. Das ◽  
B. Jayasree ◽  
Vaidhyanathan Ramamurthy
Keyword(s):  
Singlet Oxygen ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy I. Free radical absorption spectra in acetylene combustion

1953 ◽  
Vol 216 (1125) ◽  
pp. 165-183 ◽  
Keyword(s):  
Absorption Spectra ◽  
Total Pressure ◽  
Flash Photolysis ◽  
Initial Period ◽  
Kinetic Spectroscopy ◽  
Radical Concentration ◽  
Stage 4 ◽  
Explosive Reaction ◽  
Stage 1 ◽  
Flash Spectroscopy

The explosive oxidation of acetylene, initiated homogeneously by the flash photolysis of a small quantity of nitrogen dioxide, has been investigated by flash spectroscopy. The absorption spectra of OH, CH, C 2 (singlet and triplet), C 3 , CN and NH, a number of which have not previously been observed, are described, and the relative concentrations, at all times throughout the explosion, are given. Four stages have been distinguished in the explosive reaction: 1. An initial period during which only OH appears. 2. A rapid chain branching involving all the diatomic radicals. 3. Further reaction, occurring only when oxygen is present in excess of equimolecular proportions, during which the OH concentration rises exponentially and the other radicals are totally consumed. 4. A relatively slow exponential decay of the excess radical concentration remaining after completion of stages 2 and 3. The duration of stage 1 is 0 to 3 ms. In an equimolecular mixture at 20 mm total pressure, containing 1.5 mm NO 2 , the durations of both stage 2 and stage 3 are approximately 10 -4 s and the half-life of OH in stage 4 is 0.28 ms. A preliminary interpretation of these changes and of the radical reactions is given.

The polymerization of styrene sensitized by molecules in the triplet state II. Kinetics and mechanism

1959 ◽  
Vol 251 (1264) ◽  
pp. 4-26 ◽  
Keyword(s):  
Triplet State ◽  
Aromatic Hydrocarbons ◽  
Flash Photolysis ◽  
Radical Addition ◽  
Photochemical Reactions ◽  
Kinetics And Mechanism ◽  
Qualitative Investigation ◽  
Initiation Mechanism ◽  
Initial Formation ◽  
Mechanism Of The Reaction

The kinetics and mechanism of the reaction between anthracene and styrene have been fully investigated. By means of flash photolysis techniques, it has been confirmed that it is the triplet state of anthracene which sensitizes the polymerization. It has also been shown that both triplet and unexcited singlet anthracene copolymerize with styrene, the former with a zero activation energy. The work has been extended to the polymerizations sensitized by pyrene and chrysene, and to the unsensitized photopolymerization of styrene. It has been shown that in every case an initiation mechanism, involving the initial formation of a triplet-monomer complex, satisfactorily explains the observed results. The copolymerization rates of pyrene and chrysene were undetectable; these results, coupled with those obtained for the copolymerization of anthracene with styrene, are in agreement with the conclusions of Kooyman & Farenhorst, Szwarc, and others, concerning the reactivity of olefinic and aromatic hydrocarbons to radical addition. Finally, a qualitative investigation of the photochemical reactions between the sensitizers, and cumene and 9 .10-dihydroanthracene, has been made.

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