“…It is possible that MgOEP •+ is reduced by TEA. The accumulation of CCl 3 • radicals in this system has been ascertained in refs and , and it was concluded that the porphyrin can sensitize the reduction of many CCl 4 molecules by TEA in the TEA host matrix. 11 Accumulation of products during the photolysis of the 2 × 10 -3 M solution of MgOEP in 2-chlorobutane glass in the presence of 2.5 M CCl 4 at 75 K. Irradiation was carried out in the visible region (450−650 nm, filters ZhS-12 + SZS-23) at the intensity of 37 mW cm -2 for 1 and 15 min, respectively.…”
Section: Resultsmentioning
confidence: 58%
“…It is difficult to determine solely on the basis of optical data whether the spectra are modified by interactions with counteranions or radicals (CCl 4 •- , CCl 3 • , Cl - ), solvation of central Mg ion, or more extensive substitution and addition reactions at the π-radical itself. The electron spin resonance method may prove invaluable for proper characterization of the photooxidation products. − , The efficiency of MgOEP photolysis in different media containing 2.5 M CCl 4 is somewhat dependent on the polarity of matrix. The highest value of Φ 2 (0.01) is observed in highly dipolar ethanol and propylene carbonate.…”
Section: Resultsmentioning
confidence: 99%
“…The electron spin resonance method may prove invaluable for proper characterization of the photooxidation products. [1][2][3][4][5][6][7][8]60 The efficiency of MgOEP photolysis in different media containing 2.5 M CCl 4 is somewhat dependent on the polarity of matrix. The highest value of Φ 2 (0.01) is observed in highly dipolar ethanol and propylene carbonate.…”
Section: Resultsmentioning
confidence: 99%
“…The photoinduced redox reactions of porphyrin complexes with closed-shell metal ions in solid solutions have been considered initially as model systems of the primary processes in photosynthesis. 1 Extensive studies of photoionization of Mg and Zn porphyrins in frozen solvent glasses containing halocarbon acceptors have been performed by Khairutdinov et al [2][3][4][5][6][7][8] and Gasyna et al [9][10][11] at 77 K. The sensitized decomposition of alkyl iodides in the presence of Zn tetraphenylporphine has been found to be a two-quantum process. 12 On the contrary, it has been concluded 2,6,10 that the photooxidation of the pigment by CCl 4 and C 2 H 2 Cl 4 is a one-quantum process taking place in the first excited singlet level.…”
Section: Introductionmentioning
confidence: 99%
“…At the same time, the photoproducts and the reaction kinetics were investigated by using the broad-band irradiation and recording over a broad spectral range on a spectrophotometer. The interrelationship between the earlier broad-band studies at 77 K [1][2][3][4][5][6][7][8][9][10][11] and the HB data will be analyzed in detail. The inconsistencies existing in the literature will be pointed out.…”
Intermolecular photoprocesses in glassy solutions of magnesium
octaethylporphine (MgOEP) and zinc
tetrabenzoporphine (ZnTBP) have been investigated under one- and
two-color irradiation between 8 and 80
K. The simultaneous exposure to the pulsed laser light in
resonance with the 0−0 S1 ← S0 transition
and the
continuous blue light absorbed by the T
n
←
T1 transitions leads to a much faster hole burning than the
irradiation
with the laser light alone. This photon gating effect is observed
in many reactive solvent glasses or the
mixtures of a reactive component and the inert diluent. In solvent
glasses containing electron acceptors
(alkyl halogenides, tert-butyl peroxybenzoate, ethyl
diazoacetate) the two-quantum photooxidation results in
the bleaching of porphyrin absorption bands and formation of cation
radical absorption at 650−700 nm (in
the case of MgOEP). In the presence of electron donors
(triethylamine) and alkenes the photoreaction can
be observed only in the hole-burning regime because upon broad-band
irradiation the intensity and position
of the 0−0 band remain unchanged. The hole burning in these
systems stems from sensitized photoprocesses
leading to the rearrangement of pigment environment. The
microscopic solvent shift of the zero-phonon
transition frequency of the pigment following
cis
−
trans isomerization of the
alkene molecules or reversible
electron transfer results in the formation of a dip in absorption.
In this case “antiholes” are observed as a
result of intensity redistribution within the 0−0 band.
Depending on the height of the triplet level of the
alkene, the sensitization can take place by means of triplet energy
transfer from either the T
n
or T1
state (to
cyclooctatetraene) of the pigment. The influence of concentration,
chemical structure, reduction potential,
and the height of triplet energy level of activators as well as the
matrix properties on the efficiency of gated
hole burning has been investigated. The reactivities of aliphatic
halocarbons and amines, aromatic electron
acceptors and donors, cyclic and linear olefins with and without
electron-accepting substituents, and other
compounds have been studied. The most efficient sensitizers have
been selected and doped in the polymer
films which are more convenient for the applications of spectral hole
burning in optical data storage.
“…It is possible that MgOEP •+ is reduced by TEA. The accumulation of CCl 3 • radicals in this system has been ascertained in refs and , and it was concluded that the porphyrin can sensitize the reduction of many CCl 4 molecules by TEA in the TEA host matrix. 11 Accumulation of products during the photolysis of the 2 × 10 -3 M solution of MgOEP in 2-chlorobutane glass in the presence of 2.5 M CCl 4 at 75 K. Irradiation was carried out in the visible region (450−650 nm, filters ZhS-12 + SZS-23) at the intensity of 37 mW cm -2 for 1 and 15 min, respectively.…”
Section: Resultsmentioning
confidence: 58%
“…It is difficult to determine solely on the basis of optical data whether the spectra are modified by interactions with counteranions or radicals (CCl 4 •- , CCl 3 • , Cl - ), solvation of central Mg ion, or more extensive substitution and addition reactions at the π-radical itself. The electron spin resonance method may prove invaluable for proper characterization of the photooxidation products. − , The efficiency of MgOEP photolysis in different media containing 2.5 M CCl 4 is somewhat dependent on the polarity of matrix. The highest value of Φ 2 (0.01) is observed in highly dipolar ethanol and propylene carbonate.…”
Section: Resultsmentioning
confidence: 99%
“…The electron spin resonance method may prove invaluable for proper characterization of the photooxidation products. [1][2][3][4][5][6][7][8]60 The efficiency of MgOEP photolysis in different media containing 2.5 M CCl 4 is somewhat dependent on the polarity of matrix. The highest value of Φ 2 (0.01) is observed in highly dipolar ethanol and propylene carbonate.…”
Section: Resultsmentioning
confidence: 99%
“…The photoinduced redox reactions of porphyrin complexes with closed-shell metal ions in solid solutions have been considered initially as model systems of the primary processes in photosynthesis. 1 Extensive studies of photoionization of Mg and Zn porphyrins in frozen solvent glasses containing halocarbon acceptors have been performed by Khairutdinov et al [2][3][4][5][6][7][8] and Gasyna et al [9][10][11] at 77 K. The sensitized decomposition of alkyl iodides in the presence of Zn tetraphenylporphine has been found to be a two-quantum process. 12 On the contrary, it has been concluded 2,6,10 that the photooxidation of the pigment by CCl 4 and C 2 H 2 Cl 4 is a one-quantum process taking place in the first excited singlet level.…”
Section: Introductionmentioning
confidence: 99%
“…At the same time, the photoproducts and the reaction kinetics were investigated by using the broad-band irradiation and recording over a broad spectral range on a spectrophotometer. The interrelationship between the earlier broad-band studies at 77 K [1][2][3][4][5][6][7][8][9][10][11] and the HB data will be analyzed in detail. The inconsistencies existing in the literature will be pointed out.…”
Intermolecular photoprocesses in glassy solutions of magnesium
octaethylporphine (MgOEP) and zinc
tetrabenzoporphine (ZnTBP) have been investigated under one- and
two-color irradiation between 8 and 80
K. The simultaneous exposure to the pulsed laser light in
resonance with the 0−0 S1 ← S0 transition
and the
continuous blue light absorbed by the T
n
←
T1 transitions leads to a much faster hole burning than the
irradiation
with the laser light alone. This photon gating effect is observed
in many reactive solvent glasses or the
mixtures of a reactive component and the inert diluent. In solvent
glasses containing electron acceptors
(alkyl halogenides, tert-butyl peroxybenzoate, ethyl
diazoacetate) the two-quantum photooxidation results in
the bleaching of porphyrin absorption bands and formation of cation
radical absorption at 650−700 nm (in
the case of MgOEP). In the presence of electron donors
(triethylamine) and alkenes the photoreaction can
be observed only in the hole-burning regime because upon broad-band
irradiation the intensity and position
of the 0−0 band remain unchanged. The hole burning in these
systems stems from sensitized photoprocesses
leading to the rearrangement of pigment environment. The
microscopic solvent shift of the zero-phonon
transition frequency of the pigment following
cis
−
trans isomerization of the
alkene molecules or reversible
electron transfer results in the formation of a dip in absorption.
In this case “antiholes” are observed as a
result of intensity redistribution within the 0−0 band.
Depending on the height of the triplet level of the
alkene, the sensitization can take place by means of triplet energy
transfer from either the T
n
or T1
state (to
cyclooctatetraene) of the pigment. The influence of concentration,
chemical structure, reduction potential,
and the height of triplet energy level of activators as well as the
matrix properties on the efficiency of gated
hole burning has been investigated. The reactivities of aliphatic
halocarbons and amines, aromatic electron
acceptors and donors, cyclic and linear olefins with and without
electron-accepting substituents, and other
compounds have been studied. The most efficient sensitizers have
been selected and doped in the polymer
films which are more convenient for the applications of spectral hole
burning in optical data storage.
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