Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene

2021 ◽  
Author(s):  
Jordan M. Cox ◽  
Matthew Bain ◽  
Michael Kellogg ◽  
Stephen E. Bradforth ◽  
Steven A. Lopez
Keyword(s):  
Photochemical Isomerization

The role of the excited-state geometry in the photochemical isomerization of bis(glycinato) platinum (II)

1967 ◽  
Vol 1 ◽  
pp. 76-80 ◽  
Author(s):  
F. Scandola ◽  
O. Traverso ◽  
V. Balzani ◽  
G.L. Zucchini ◽  
V. Carassiti
Keyword(s):  
Excited State ◽  
Photochemical Isomerization

scholarly journals Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene

2021 ◽  
Author(s):  
Jordan Cox ◽  
Mike Kellogg ◽  
Matthew Bain ◽  
Stephen E. Bradforth ◽  
Steven Lopez
Keyword(s):  
Reaction Pathway ◽  
Stokes Shift ◽  
Vibronic Coupling ◽  
Absorption Bands ◽  
Time Resolved ◽  
Photochemical Isomerization ◽  
Dynamics Simulations ◽  
Highly Strained ◽  
Holistic Description

Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly-strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the socalled “perfluoro effect,” the resulting electronic structure and photochemical reactivity of hexafluorobenzene are still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4πelectrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ~100 nm Stokes shift in fluorescence– in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway towards hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.

scholarly journals Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene

2021 ◽  
Author(s):  
Jordan Cox ◽  
Mike Kellogg ◽  
Matthew Bain ◽  
Stephen E. Bradforth ◽  
Steven Lopez
Keyword(s):  
Reaction Pathway ◽  
Stokes Shift ◽  
Vibronic Coupling ◽  
Absorption Bands ◽  
Time Resolved ◽  
Photochemical Isomerization ◽  
Dynamics Simulations ◽  
Highly Strained ◽  
Holistic Description

Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly-strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the socalled “perfluoro effect,” the resulting electronic structure and photochemical reactivity of hexafluorobenzene are still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4πelectrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ~100 nm Stokes shift in fluorescence– in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway towards hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.

scholarly journals Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene

2021 ◽  
Author(s):  
Jordan Cox ◽  
Mike Kellogg ◽  
Matthew Bain ◽  
Stephen E. Bradforth ◽  
Steven Lopez
Keyword(s):  
Reaction Pathway ◽  
Stokes Shift ◽  
Vibronic Coupling ◽  
Absorption Bands ◽  
Time Resolved ◽  
Photochemical Isomerization ◽  
Dynamics Simulations ◽  
Highly Strained ◽  
Holistic Description

Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly-strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the socalled “perfluoro effect,” the resulting electronic structure and photochemical reactivity of hexafluorobenzene are still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4πelectrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ~100 nm Stokes shift in fluorescence– in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway towards hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.

scholarly journals Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene

2021 ◽  
Author(s):  
Jordan Cox ◽  
Mike Kellogg ◽  
Matthew Bain ◽  
Stephen E. Bradforth ◽  
Steven Lopez
Keyword(s):  
Reaction Pathway ◽  
Stokes Shift ◽  
Vibronic Coupling ◽  
Absorption Bands ◽  
Time Resolved ◽  
Photochemical Isomerization ◽  
Dynamics Simulations ◽  
Highly Strained ◽  
Holistic Description

Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly-strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the socalled “perfluoro effect,” the resulting electronic structure and photochemical reactivity of hexafluorobenzene are still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4πelectrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ~100 nm Stokes shift in fluorescence– in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway towards hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor

Role of the allergist in diagnosis and management of patients with uveitis

JAMA ◽  
1966 ◽  
Vol 195 (3) ◽  
pp. 167-172 ◽  
Author(s):  
T. E. Van Metre
Keyword(s):  
Diagnosis And Management

The power of norms to sway fused group members

2018 ◽  
Vol 41 ◽  
Author(s):  
Winnifred R. Louis ◽  
Craig McGarty ◽  
Emma F. Thomas ◽  
Catherine E. Amiot ◽  
Fathali M. Moghaddam
Keyword(s):  
Evolutionary Anthropology ◽  
Normative Systems ◽  
Violent Extremism ◽  
Identity Fusion ◽  
Group Members

AbstractWhitehouse adapts insights from evolutionary anthropology to interpret extreme self-sacrifice through the concept of identity fusion. The model neglects the role of normative systems in shaping behaviors, especially in relation to violent extremism. In peaceful groups, increasing fusion will actually decrease extremism. Groups collectively appraise threats and opportunities, actively debate action options, and rarely choose violence toward self or others.

Elaborating the role of reflection and individual differences in the study of folk-economic beliefs

2018 ◽  
Vol 41 ◽  
Author(s):  
Kevin Arceneaux
Keyword(s):  
Decision Making ◽  
Individual Differences ◽  
Cognitive Processes ◽  
Evolutionary History ◽  
Behavioral Responses ◽  
History Of ◽  
Economic Beliefs

AbstractIntuitions guide decision-making, and looking to the evolutionary history of humans illuminates why some behavioral responses are more intuitive than others. Yet a place remains for cognitive processes to second-guess intuitive responses – that is, to be reflective – and individual differences abound in automatic, intuitive processing as well.

The role of affect in feelings of obligation

2020 ◽  
Vol 43 ◽  
Author(s):  
Stefen Beeler-Duden ◽  
Meltem Yucel ◽  
Amrisha Vaish
Keyword(s):  
Positive Emotions ◽  
The Creation ◽  
Sense Of Obligation

Abstract Tomasello offers a compelling account of the emergence of humans’ sense of obligation. We suggest that more needs to be said about the role of affect in the creation of obligations. We also argue that positive emotions such as gratitude evolved to encourage individuals to fulfill cooperative obligations without the negative quality that Tomasello proposes is inherent in obligations.

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