Solvent effects on the quenching of the equilibrating n,π* and π,π* triplet states of 9,10-phenanthrenequinone by 2-propanol

Nicodem, David E.; Silva, Rosaly S.; Togashi, Denísio M.; Cunha, Maria Fernanda V. da

doi:10.1016/j.jphotochem.2005.04.029

Cited by 26 publications

(28 citation statements)

References 17 publications

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“…For acetonitrile we were able to measure a self-quenching rate constant of 3.1 × 10 8 L mol −1 s −1 . A similar value (2.0 × 10 8 L mol −1 s −1 ) was found for the triplet of 9,10phenanthrenequinone (1) in the same solvent [20]. The transient from irradiation of 3 is quenched by ␤-carotene (E T = 21 kcal mol −1 ) [39] with a diffusion controlled rate constant, leading to the formation of a 520 nm band characteristic of the ␤-carotene triplet.…”

Section: Laser Flash Photolysissupporting

confidence: 57%

“…The photochemistry of ␣-diketones (and the closely related ortho-quinones) has been a subject of interest for a long time and this field of investigation has continued to be very active [6]. Several ortho-quinones have been found to be photoreactive in the presence of hydrogen and electron donors [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

“…The reactivity of aromatic ketones is dependent on the nature of their lowest triplet excited state, with the n,* triplet being the reactive state [25]. Where the ketones have a lowest ,* triplet state it has been accepted that they react predominantly via the higher energy n,* state, populated thermally from the lower energy state [20,26,27]. The photoreactivity of 9,10-phenanthrenequinone (1) and other triplets [17,20] has been observed to be dependent upon the solvent polarity and is related to a small energy separation between the n,* and ,* triplet levels, thus leading to an inversion of the configuration.…”

Section: Introductionmentioning

confidence: 99%

“…Where the ketones have a lowest ,* triplet state it has been accepted that they react predominantly via the higher energy n,* state, populated thermally from the lower energy state [20,26,27]. The photoreactivity of 9,10-phenanthrenequinone (1) and other triplets [17,20] has been observed to be dependent upon the solvent polarity and is related to a small energy separation between the n,* and ,* triplet levels, thus leading to an inversion of the configuration. On the other hand, quinone 2 does not show an inversion of the triplet state, and is found to be ,* in all solvents.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A combined laser flash photolysis, density functional theory and atoms in molecules study of the photochemical hydrogen abstraction by pyrene-4,5-dione

Lucas

Elias

Firme

et al. 2009

Journal of Photochemistry and Photobiology A: Chemistry

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Section: Laser Flash Photolysissupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A combined laser flash photolysis, density functional theory and atoms in molecules study of the photochemical hydrogen abstraction by pyrene-4,5-dione

Lucas

Elias

Firme

et al. 2009

Journal of Photochemistry and Photobiology A: Chemistry

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“…[32][33][34] A eficiência da reação depende da força da ligação R-H do doador de hidrogênio, da energia e da configuração do estado excitado (n,π* ou π,π*). 32,33,35 A reação pode ocorrer tanto no estado singlete quanto no estado triplete mas, no caso de cetonas aromáticas, ocorre exclusivamente através de um estado excitado triplete devido aos valores altos para o rendimento quântico de cruzamento intersistemas. Cetonas que possuem o estado triplete (n,π*) como o de menor energia abstraem hidrogênio eficientemente, enquanto o triplete de cetonas (π,π*) o fazem com eficiência baixa.…”

Section: Fotoquímica De Cetonasunclassified

Photochemistry of Naphthoquinones

Lucas¹,

Ferreira²,

Netto‐Ferreira³

2015

Revista Virtual De Química

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Quinones are widely distributed in living organisms, are present in medicines and used as reagents by chemists. In nature, certain benzoquinones are so commonly found that they are called ubiquinones (ubiquitous); others, the plastoquinones, participate in the process of photosynthesis, without being directly excited by light. These processes will not be seen here. The participation of excited quinones in the generation of singlet oxygen and other reactive oxygen species (ROS) will be addressed. The photochemistry of quinones, which are colored compounds, has been studied since the mid-XIX century, with Klinger; in Part 1, after the Introduction, we will present a summary of the most relevant results, so far, mainly for naphthoquinones, starting with fundamental concepts of organic photochemistry of ketones. We will see, for example, how biological quinones can, when excited by light, deactivate without generating harmful reactive species. In Part 2 some of the spectroscopic techniques with lasers, used in contemporary photochemistry will be reviewed. And, finally, these techniques will be applied to the study of naphthoquinones related to natural products and the results will be discussed.

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Time‐Resolved Spectroscopy: Instrumentation and Applications

Ariese

Roy

Venkatraman

et al. 2017

Encyclopedia of Analytical Chemistry

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Light–matter interaction may lead to three fundamental phenomena, viz. (i) absorption, (ii) emission, and (iii) scattering. Spectroscopic techniques based on these phenomena are used to characterize the materials of interest, not only stable compounds but also short‐lived species during molecular transformations. Determining the electronic and molecular structure of the transient species is crucial in order to understand various photochemical, physical, and biological processes of fundamental and technological importance. Identifying various redox species during photosynthesis, understanding the photoinduced charge transfer process in solar cells, unraveling the photochemistry of vision that involves photoisomerization of retinal, etc. require spectroscopic techniques that can resolve various transient species in time and were practically impossible until the advent of pulsed lasers. The absorption of a photon by a molecule may initiate a cascade of dynamic molecular events, namely vibrational relaxation (VR), solvation dynamics, internal conversion (IC), intersystem crossing (ISC), electron transfer, isomerization reactions, etc., which can occur at femtosecond (fs) to picosecond (ps) timescales. Bimolecular reaction dynamics in liquids, such as H‐atom abstraction reaction, are typically diffusion controlled and therefore can be observed at nanosecond (ns) timescales. Therefore, time‐dependent (time‐resolved) spectroscopy has been an exquisite tool to follow the molecular dynamics after an initial phototrigger. Apart from studying molecular dynamics, time resolution can also be used to distinguish conformers, isomers or enantiomers, or distinguish identical compounds in different environments. It can also be applied to suppress unwanted signals occurring at different timescales, for instance fluorescence suppression in Raman experiments, or selectively detect compounds deeper inside a sample. In this article, we first give an introduction to the fundamentals of time‐resolved electronic absorption, spontaneous excited‐state resonance Raman, and coherent Raman scattering and emission techniques, spanning the range from femtosecond to microsecond timescales. Important technical aspects of time‐resolved spectroscopic equipment are also discussed. We then present some examples of cis–trans isomerization, thermal equilibrium of the two lowest triplet states, H‐atom abstraction reactions, etc. and demonstrate the molecular dynamic events after an initial phototrigger by a comprehensive kinetic analysis of the peak position, width and intensity of the marker bands in the time‐resolved electronic absorption, and Raman and emission spectra.

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Solvent effects on the quenching of the equilibrating n,π* and π,π* triplet states of 9,10-phenanthrenequinone by 2-propanol

Cited by 26 publications

References 17 publications

A combined laser flash photolysis, density functional theory and atoms in molecules study of the photochemical hydrogen abstraction by pyrene-4,5-dione

A combined laser flash photolysis, density functional theory and atoms in molecules study of the photochemical hydrogen abstraction by pyrene-4,5-dione

Photochemistry of Naphthoquinones

Time‐Resolved Spectroscopy: Instrumentation and Applications

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