The Triplet State of 3‐Nitropyrene

Scheerer, R.; Henglein, A.

doi:10.1002/bbpc.19770811208

Cited by 19 publications

(31 citation statements)

References 12 publications

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“…The triplet decay rate for bromopyrene in methanol after purification was 19 µs compared to a literature value of 20 µs. 10 Before use, coronene and anthracene were recrystallized from ethanol, and the fluorescence decay lifetimes and absorbance spectra matched the literature results.…”

Section: Methodsmentioning

confidence: 93%

Reactions of Pyrene Excited States with Oxygen on the Surface of Porous Silica Gel and Similar Surfaces

Ruetten

Thomas

1999

J. Phys. Chem. B

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Oxygen quenching of the singlet state of pyrene adsorbed on amorphous silica gel is studied by pulsed laser and rapid spectrophotometric methods. The quenching rate constant depends on the pore size of the silica and the method and temperature used to remove adsorbed water and surface silanol groups. The two possible mechanisms for O 2 quenching of excited pyrene on an SiO 2 surface are quenching by direct collision encounter on the excited state (Eley-Rideal) and quenching by surface adsorbed oxygen (Langmuir-Hinshelwood). In the present system, these two mechanisms are distinguished using temperature studies. Both mechanisms are operative in the current system: the Eley-Rideal mechanism dominates at temperatures greater than 30°C, and the Langmuir-Hinshelwood mechanism dominates at lower temperatures, T < 10°C. Several other surfaces are also briefly studied in order to add insight into the surface processes which are involved. One product of the oxygen quenching of the singlet excited state is the triplet state. Quenching of the singlet state leads to an increase in the triplet yield for pyrene and coronene. However, the efficiency of the oxygeninduced intersystem crossing is much smaller on the SiO 2 surface compared to that in solution. The pyrene triplet excited state is also quenched by oxygen. Unlike the singlet state, the quenching mechanism is predominantly Eley-Rideal or direct collision of oxygen with the excited triplet state on the surface. The efficiency of the triplet quenching decreases with increasing oxygen pressure. This is explained by the formation of an intermediate O 2 -triplet state complex.

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Section: Methodsmentioning

confidence: 93%

Reactions of Pyrene Excited States with Oxygen on the Surface of Porous Silica Gel and Similar Surfaces

Ruetten

Thomas

1999

J. Phys. Chem. B

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“…Similar high triplet yields have been reported for other nitro-PAHs. 11,14,15,27,28 Attention is now shifted to the transient species at 445 nm. As shown in Figures 3i and S3, this transient species persists after the triplet-state signal has decayed, regardless of whether N 2 , O 2 , or ferrocene is added to the solution.…”

Section: The Journal Of Physical Chemistry Lettersmentioning

confidence: 98%

“…Recent time-resolved investigations of mononitropyrenes − and nitronaphthalenes − have shown that ultrafast intersystem crossing occurs through a doorway triplet state (T n ), which leads to the population of the lowest-energy triplet state (T 1 ) in high yield. A stable aryloxy radical has also been characterized, ,,− , which leads to the formation of several major products. − , The excited-state mechanism by which this radical intermediary is formed is uncertain and continues to be a topic of debate. ,− ,− ,− ,, …”

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confidence: 99%

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The Photochemical Branching Ratio in 1,6-Dinitropyrene Depends on the Excitation Energy

Brister

Piñero-Santiago

Morel

et al. 2016

J. Phys. Chem. Lett.

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Nitropolycyclic aromatic hydrocarbons constitute one of the most disconcerting classes of pollutants. Photochemical degradation is thought to be a primary mode of their natural removal from the environment, but the microscopic mechanism leading to product formation as a function of excitation wavelength is poorly understood. In this Letter, it is revealed that excitation of 1,6-dinitropyrene with 425, 415, or 340 nm radiation leads to an increasing amount of radical production through photodissociation at the expense of triplet-state population-the two primary reaction pathways in this class of pollutants. Radical formation requires overcoming an energy barrier in the excited singlet manifold. This activation energy explains the large fraction of the initial singlet-state population that intersystem crosses to a doorway triplet state, instead of leading overwhelmingly to photodissociation. The unforeseen excitation wavelength dependence of this branching process is expected to regulate the photochemistry of 1,6-dinitropyrene and possibly of other nitroaromatic pollutants in the environment.

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“…Significant differences were also observed when their photochemical behavior in the surfaces was compared to that in solution. 10 Studies on the characterization of the participating excited states and reactive intermediate species in the photochemistry of nitropyrenes are mostly limited to the mononitropyrenes. 10−18 The excited-state dynamics and primary photochemical processes of nitronaphthalene 19−27 and nitroanthracene 28 derivatives have also received prominent attention, whereas investigations focusing on the excited-state dynamics of dinitropyrenes have received less scrutiny.…”

Section: Introductionmentioning

confidence: 99%

Photochemical Relaxation Pathways in Dinitropyrene Isomer Pollutants

et al. 2017

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Dinitropyrenes are polycyclic aromatic pollutants prevalent in the environment. While their transformations by sunlight in the environment have been documented, the effect that the nitro-group substitution pattern has on the relaxation pathways has not been extensively studied. In this contribution, the steady-state and femtosecond-to-microsecond excited-state dynamics of 1,3-dinitropyrene and 1,8-dinitropyrene isomers are investigated upon visible light excitation at 425 nm and compared with those recently reported for the 1,6-dinitropyrene isomer. The experimental results are complemented with ground- and excited-state density functional calculations. It is shown that excitation at 425 nm results in the ultrafast branching of the excited-state population in the S state to populate the triplet state in ca. 90% yield and to form a nitropyrenoxy radical in less than 10% yield. In addition, the position of the NO group does not affect significantly the excited-state relaxation mechanism, while it does influence the absorption and fluorescence spectra, the fluorescence, triplet, singlet oxygen, and photodegradation yields, as well as the relative yield of radical formation. Radical formation is implicated in the photodegradation of these pollutants, while in the presence of hydrogen donors, direct reactions from the triplet state are also observed.

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The Triplet State of 3‐Nitropyrene

Cited by 19 publications

References 12 publications

Reactions of Pyrene Excited States with Oxygen on the Surface of Porous Silica Gel and Similar Surfaces

Reactions of Pyrene Excited States with Oxygen on the Surface of Porous Silica Gel and Similar Surfaces

The Photochemical Branching Ratio in 1,6-Dinitropyrene Depends on the Excitation Energy

Photochemical Relaxation Pathways in Dinitropyrene Isomer Pollutants

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