Pathways for Formation of Hydrated Electrons From Excited Phenol and Related Compounds

Grabner, Gottfried; Köhler, Gabriele; Zechner, Josef; Getoff, N.

doi:10.1111/j.1751-1097.1977.tb07514.x

Cited by 68 publications

(88 citation statements)

References 40 publications

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“…Accordingly, these models do not apply to shift phenomena in aqueous solutions of phenolic compounds (1,25). This observation is in broad agreement with the inadequacy of general liquid state parameters, such as the static dielectric constant or Kosower's parameter Z, to account for the observed solvent effect on photophysical and photochemical processes of these compounds, especially in aqueous solutions and in aqueous/organic mixtures.…”

supporting

confidence: 56%

“…between solvent and fluorescence behaviour in the Many of the effects observed could be explained by case of the systems studied; the decrease of QF at a general theory of electrostatic interactions (1). higher excitation energies is related to the static However, the influence of solute-solvent interac-dielectric constant in a non-linear way (12).…”

Section: Introductionmentioning

confidence: 99%

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The role of the molecular environment for the primary photoprocesses of phenol in solution

Zechner¹,

Köhler²,

Grabner³

et al. 1980

Can. J. Chem.

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Can. J. Chem. 58,2006 (1980. Quantum yields of fluorescence as well as of solvated electron and H atom formation have been measured for phenol in several pure solvents and mixtures of varyingpolarity. The influence of excitation energy has been studied by excitation ofphenol in the first and second excited singlet states. The solvent dependences of fluorescence and photoejection parameters are strongly correlated. The results are interpreted in terms of specific solute-solvent interactions, in particular H-bonded structures.J. ZECHNER, G. KOHLER, G. G R A B N E~ et N. GETOFF. Can. J. Chem. 58,2006Chem. 58, (1980. Introduction the static dielectric constant (12) or Kosower's Solvent effects on photophysical properties of micropolarity parameter Z (6, 13)-These investimolecules are well known from studies of spectral gations showed that there is no simple relationship energy shifts between gas phase and solution. between solvent and fluorescence behaviour in the Many of the effects observed could be explained by case of the systems studied; the decrease of QF at a general theory of electrostatic interactions (1). higher excitation energies is related to the static However, the influence of solute-solvent interac-dielectric constant in a non-linear way (12). he tions on excited state decay processes and primary behaviour of Q F in different classes of solvents photochemical reactions is less well understood.(hydrocarbons, polar organic solvents, water) is various studies carried out during the last reflected in a different dependence on Z within each years have demonstrated, simple aromatic molethese (I3)-cules such as phenols, anilines, indoles, andThe aim of the present study was to obtain more aromatic amino acids share the interesting photo-information about solvent effects on primary physical property of having a fluorescence quan-~h o~o~r o c e s s e s f~o m S I and& states ofphenol. To yield (Q,) which is not independent of the this effect, the influence of excitation energy on the energy of excitation (2-5). It has been early recogquantum yield as as On nized that this effect is strongly influenced by the photoejection and H atom formation by OH bond solvent environment: the dependence of e F o n ex-rupture has been investigated in pure ~o l a r and citation energy is pronounced in hydrocarbon sol-apolar solvents and in solvent mixtures. Particular vents, small in polar organic solvents, but notable has been paid the possible of again in water (2, 6). A correlation between the Specific S~lUte-S~l~ent interactions On these proeffect on QFand the hydrogen bonding capability of cesses. the solvent was suggested in the case of phenol (7).Experimental Section Furthermore, a connection with excitation

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confidence: 56%

Section: Introductionmentioning

confidence: 99%

The role of the molecular environment for the primary photoprocesses of phenol in solution

Zechner¹,

Köhler²,

Grabner³

et al. 1980

Can. J. Chem.

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“…Flash photolysis studies have shown that phenol and substituted phenols exhibit a variety of interesting photophysical and photochemical properties [1][2][3][4][5][6][7][8][9]. Depending on solvent, photoexcitation can lead to photoionization and/or O-H bond dissociation.…”

Section: Introductionmentioning

confidence: 99%

“…Depending on solvent, photoexcitation can lead to photoionization and/or O-H bond dissociation. In some cases, the fluorescence quantum yield was Presented at the Sixth International Symposium on Magnetic Field and Spin Effects in Chemistry and Related Phenomena, August 21-26, 1999, Switzerland found to depend strongly on excitation energy and this has been correlated with the excitation-energy-dependent formation of hydrated electrons in aqueous solution [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

FT-EPR study of the pH dependence of the photochemistry of sesamol in aqueous solution

1999

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A Fourier transform electron paramagnetic resonance (FT-EPR) study was made of the photochemistry of 3,4-methylenedioxyphenol (sesamol, SEOH)) in aqueous solution. FT-EPR measurements show that in alkaline (pH 11) solution, pulsed-laser excitation of SEO -leads to photoionization giving the hydrated electron and SEO free radical. Resonance signals from these paramagnetic species develop with instrument-controlled rise time. They exhibit a low-field emission/ high-field absorption (E/A) CIDEP pattern with the transition from emission to absorption occurring at the resonance of the hydrated electron. It is shown that the spin polarization stems from contributions from the ST o radical pair mechanism (E/A) and triplet mechanism (A). From this it is concluded that photoionization of sesamol occurs via the triplet excited state. in neutral and acidic (pH 4-7) aqueous solution, photoexcitation generates SEO' and cyclohexadienyl-type radicals. In this case, radicals grow in over a period of 1-2 is and FT-EPR spectra display an E/A pattern with the inversion point in the center. The lowering of the pH of the solution apparently is accompanied by a strong reduction in the relative importance of photoionization. From the FT-EPR data it can be deduced that in neutral and acidic solutions the dominant reaction channel is H-atom transfer. In this respect, the photochemistry of sesamol differs from that of phenol and pcresol. For these phenols the change in pH does not affect the appearance of the FT-EPR spectra. Apparently, the change in electronic structure caused by the methylenedioxy substituent strongly affects the excited state reactivity of sesamol.

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“…The transient absorption spectra resulting from PP and QP were obtained by means of a conventional flash photolysis apparatus (Northern Precision, modi fied: air-filled flash lamp, flash duration 7 (is with vari able energy of 20-200 J) described earlier [27]. The detection of each individual signal was now improved by a Philips digital storage oscilloscope (PM 3320/40) in connection with a Sharp PC-4500.…”

Section: Conventional Flash Photolysismentioning

confidence: 99%

Steady-State and Flash Photolysis Investigations of 1 H-Indene-l,3(2H)-Dione Derivatives

Grabner

Quint

Getoff

et al. 1991

Zeitschrift Für Naturforschung A

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Pyrophthalone (PP, 2-(2-pyridinyl)-l H-indene-l,3(2H)-dione) and quinophthalone (QP, 2-(2-quinolinyl)-l H-indene-l,3(2 H)-dione) were investigated in various solvents with respect to their photostability. It was found that PP and QP in ethanol as well as QP in cyclohexane are rather stable under steady-state conditions using UV light (A = 253.7 nm). Conventional as well as laser flash photolysis of airfree aqueous alkaline solutions (pH 12) lead to the formation of different radicals and solvated electrons (eã). Some reaction rates were determined and probable reaction mechanisms were postu lated.

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Pathways for Formation of Hydrated Electrons From Excited Phenol and Related Compounds

Cited by 68 publications

References 40 publications

The role of the molecular environment for the primary photoprocesses of phenol in solution

The role of the molecular environment for the primary photoprocesses of phenol in solution

FT-EPR study of the pH dependence of the photochemistry of sesamol in aqueous solution

Steady-State and Flash Photolysis Investigations of 1 H-Indene-l,3(2H)-Dione Derivatives

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