An ESR study of the photolysis of methanol adsorbed on silica gel

Bobrovskii, A. P.; Kholmogorov, V. E.

doi:10.1007/bf00523736

Cited by 2 publications

(7 citation statements)

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“…Spectrophotometric Study of MgOEP in the Presence of Electron Acceptors. Photooxidation of metalloporhyrins in solvent glasses containing electron acceptors at 77 K have been used as a model reaction of primary processes in photosynthesis. ,, It has been concluded that photoionization of Zn tetraphenylporphine in C 2 H 5 OH/1 M CCl 4 2 or 2-chlorobutane/CCl 4 (1:1 v/v) 11 and similar vitreous systems at 77 K takes place in the first excited singlet state as a result of the absorption of a single quantum. On the contrary, the photon-gated HB experiments suggest that the efficient electron ejection should occur from the highly excited triplet state, i.e., after absorption of a second light quantum by the molecule in the T 1 state.…”

Section: Resultsmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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Hole-Burning Study of Primary Photochemistry of Metalloporphyrins in Reactive Solvent Glasses

Renge

Wild

1997

J. Phys. Chem. A

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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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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hole-Burning Study of Primary Photochemistry of Metalloporphyrins in Reactive Solvent Glasses

Renge

Wild

1997

J. Phys. Chem. A

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Photophysics of Reduced Silicon Tetraphenylporphyrin

Song¹,

Cissell²,

Vaid³

et al. 2007

J. Phys. Chem. B

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The contrasting photophysical properties of two silicon (IV) tetraphenylporphyrins, Si(TPP)(py)2 and Si(TPP)Cl2, have been investigated using static absorption and fluorescence spectroscopy and ultrafast transient absorption measurements. The parent Si(TPP)Cl2, in which the porphyrin macrocycle has its normal 2- oxidation state, has a fluorescence yield of 0.027, and a lifetime of 1.8 ns for the lowest excited singlet state. In marked contrast, the reduced, anti-aromatic complex Si(TPP)(py)2, with the macrocycle in the 4- oxidation state, has an extremely low fluorescence yield (< or =0.0004) and a 750-fold shorter excited-state lifetime (2.4 ps) in the same solvent (pyridine). The rapid deactivation of photoexcited Si(TPP)(py)2 to the ground state is likely associated with its ruffled structure and the presence of low-energy excited states in its electronic manifold.

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An ESR study of the photolysis of methanol adsorbed on silica gel

Cited by 2 publications

References 1 publication

Hole-Burning Study of Primary Photochemistry of Metalloporphyrins in Reactive Solvent Glasses

Hole-Burning Study of Primary Photochemistry of Metalloporphyrins in Reactive Solvent Glasses

Photophysics of Reduced Silicon Tetraphenylporphyrin

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