Primary photochemical processes in aromatic molecules. Part 8.—Absorption spectra and acidity constants of anilino radicals

Land, Edward J.; Porter, Gerald B.

doi:10.1039/tf9635902027

Cited by 153 publications

(61 citation statements)

References 3 publications

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“…The decay lifetime of the MB excited singlet states is shown to decrease with increasing dielectric constant in the protic solvents studied, Figure 5. This is expected owing to the interaction of the polar solvent with MB [18][19][20]. In protic alcohol and aqueous solutions the excited state dipole of MB is expected to be higher than that of that of the ground state [21], therefore, the energy gap between the singlet and triplet states decreases and the relaxation rate is increased, Figure 5.…”

Section: Picosecond Transient Absorption Spectra and Kineticsmentioning

confidence: 91%

Time resolved spectroscopic studies of methylene blue and phenothiazine derivatives used for bacteria inactivation

Chen

Cesario

Rentzepis

2010

Chemical Physics Letters

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Section: Picosecond Transient Absorption Spectra and Kineticsmentioning

confidence: 91%

Time resolved spectroscopic studies of methylene blue and phenothiazine derivatives used for bacteria inactivation

Chen

Cesario

Rentzepis

2010

Chemical Physics Letters

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“…By the loss of one electron aniline becomes a weak acid of pK a = 7 in water [52]. From the equilibrium constant of K = 10 -7 M and a maximum rate constant for the association of lOll M-I S-I [53] it follows that the dissociation rate constant cannot be faster than 10 4 s -I.…”

Section: (Ft:d +) (K'mentioning

confidence: 99%

“…To obtain a relative measure of the radical yield <Pro the optical density at the maximum (425 nm) of thiopyronine semiquinone absorption was used, where the oxidized donor radicals contribute only about 5070 to the optical density (6 "" 2000 M-1 cm -I [52]). The donor concentrations used (10-3 to 10-2 M) were high enough to achieve almost complete triplet quenching, however still low enough that singlet quenching was negligible.…”

Section: Influence Of Solvent Viscositymentioning

confidence: 99%

Heavy Atom Substituents as Molecular Probes for Solvent Effects on the Dynamics of Short‐lived Triplet Exciplexes

Winter

Steiner

1980

Ber Bunsenges Phys Chem

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The influence of heavy atom substituents (Br, I) in the electron donor aniline on the electron transfer reaction with thiopyronine triplet is investigated by flash spectroscopy in solvents of different viscosity and polarity. Triplet quenching constants and radical yields are determined. The results are analysed in terms of decay constants of an intermediate triplet exciplex where the heavy atom substituents significantly enhance the intersystem crossing process leading to singlet ground state formation and thus diminishing the radical yield due to exciplex dissociation. The sensitivity of the radical yield to solvent effects is strongly enhanced by heavy atom substitution though the solvent effects proper on the exciplex dynamics are substituent independent. The heavy atom effect is used to study the solvent cage effect on exciplex dissociation by means of viscosity variation. The exciplex dissociation lifetime is proportional to solvent viscosity, however, it contains a constant contribution which may be attributed to exciplex bonding. By means of the heavy atom probes it is found that increasing solvent polarity intersystem crossing in the exciplex is favored over exciplex dissociation into radicals. A tentative explanation is given in terms of solvent polarity dependence of the electronic energy gap between exciplex and corresponding Franck-Condon ground state. (1) and (2) it follows that the radical yield is determined by three factors, characterizing the behaviour of the triplet exciplex (Eq. (4» where 'Hal is the atomic spin-orbit coupling constant of the halogen and C 2 (POSHaJ is the Hiickel spin density transferred to the position of the halogen atom by the electron transfer. The latter factor readily explains the positional dependence of the substituent effect (para > ortho > meta).(1)The rate determining step in the quenching of the excited cationic dye triplet eA +) by the electron donor (D) is the formation of a triplet exciplex with radical-pair-like electronic structure e(A'D +». The triplet exciplex has two decay channels: dissociation to the free radicals (rate constant k fr ) and intersystem crossing with back transfer of the electron to the donor leading to the formation of the ground state of the reaction partners (rate constant k isc ) ' The radical yield observed is determined by the two decay constants of the exciplex:triplet exciplexes can be detected by their phosphorescence under such conditions. In a recent paper [22] we provided indirect evidence for the formation of triplet exciplexes as intermediates in electron transfer reactions. We studied the reaction of thionine triplet as an electron acceptor with aniline and its monohalogen derivatives as electron donors in methanol. In these reactions the halogen substituents have systematic influence on the radical yield (extrapolated to complete triplet quenching) which could be explained satisfactorily by the following mechanism, strongly supported by a recently determined magnetic field effect [23]:The analysis of the radical yield...

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“…Amines have been shown to react with radiolytic cations (1 7, [25][26][27][28]. Increasing the pressure on the aniline solutions increased the scavenging efficiency (Fig.…”

Section: ]mentioning

confidence: 99%

“…To obtain further evidence about the effect of pressure on positive ion reaction efficiencies, aniline was used as a scavenger (25)(26)(27)(28). Amines have been shown to react with radiolytic cations (1 7, [25][26][27][28].…”

Section: ]mentioning

confidence: 99%

Effect of Pressure on the Rates of Reaction of Radiolysis Intermediates in Liquid n-Hexane

Jha¹,

Freeman²

1971

Can. J. Chem.

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The yield of hydrogen from pure hexane, G(H2) = 5.3 + 0.2 was independent of pressure in the range 1 bar to 4.6 kbars. The G values of Hz, HD, and Dz obtained from 11 mol% C6D14 in C6H14 were independent of pressure and were respectively, 4.85, 0.34, and 0.11. The electron and hydrogen atom scavenging efficiencies of carbon tetrachloride and hexadiene-1,3, and the hydrogen atom scavenging efficiency of hexene-1 were independent of pressure. The positive ion scavenging efficiencies of benzene and aniline increased with increasing pressure. The volume of activation for the hydrogen atom reaction with n-hexane is essentially the same as that for the reaction with hexene-1. The pressure dependence of the charge scavenging reactions has been interpreted in terms of the kinetics of spur processes. The treatment is consistent with the fact that the efficiency of the electron scavenging reactions is independent of pressure. The increased efficiency of positive ion reaction under pressure implies that the ratio of the diffusion coefficients of the radiolytic positive ion and electron, D + / D -, increases with increasing pressure.Le rendement en hydrogene pour I'hexane pur, G(H2) = 5.3 + 0.2, est independant de la pression dans le domaine de 1 bar a 4.6 kbar. Les valeurs G de Hz, H D et Dz obtenues a partir de 11 mole% de C6D14 dans C6H14 sont independantes de la pression et sont respectivement de4.85,0.34et 0.1 1. L'efficacitk du tetrachlorure de carbone et de I'hexadiene-1,3 pour capturer les electrons et les atomes d'hydrogene ainsi que I'efficacite de I'hexene-1 pour capturer les atomes d'hydrogene est independante de la pression. L'efficacite du benzene et de I'aniline pour capturer les ions positifs augmente en mCme temps que la pression. Le volume d'activation pour la reaction d'atomes d'hydrogene avec le n-hexane est essentiellement le mCme que pour la reaction avec I'hexene-1. La dependance de la pression sur les reactions de capture des charges est interpretee en termes de cinetique des reactions dans les grapkes. L'augmentation de I'efficacite des reactions des ions positifs, sous I'effet de la pression, implique que le rapport des coefficients de diffusion des ions positifs crees sous irradiation et des electrons, D + / D -, augmente avec la pression.

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Primary photochemical processes in aromatic molecules. Part 8.—Absorption spectra and acidity constants of anilino radicals

Cited by 153 publications

References 3 publications

Time resolved spectroscopic studies of methylene blue and phenothiazine derivatives used for bacteria inactivation

Time resolved spectroscopic studies of methylene blue and phenothiazine derivatives used for bacteria inactivation

Heavy Atom Substituents as Molecular Probes for Solvent Effects on the Dynamics of Short‐lived Triplet Exciplexes

Effect of Pressure on the Rates of Reaction of Radiolysis Intermediates in Liquid n-Hexane

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