Fluorescence decay and radiative lifetimes of fluorinated aromatic molecules

Loper, G. L.; Lee, E.K.C.

doi:10.1016/0009-2614(72)80062-9

Cited by 50 publications

(18 citation statements)

References 27 publications

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“…Its fluorescence yields and lifetimes vary slowly with increasing E vib in a wide energy range: τ f = 87, 82 and 72 ns and Q f = 0.27, 0.24 and 0.19 for v = 0, 1 and 2, the levels of the main vibrational progression: 6 1 0 1 v 0 (E vib = 523 + 922v cm −1 ). A similar behaviour was observed for of a whole class of aromatic compounds, such as fluorobenzene [103], toluene and aniline [104] with onsets at about 2,500, 2,200 and 3,500 cm −1 , respectively. A similar behaviour was observed for of a whole class of aromatic compounds, such as fluorobenzene [103], toluene and aniline [104] with onsets at about 2,500, 2,200 and 3,500 cm −1 , respectively.…”

Section: Relaxation Of High S # 1 Levelssupporting

confidence: 81%

Energy Dissipation in Molecular Systems

Tramer¹,

Jungen²,

Lahmani³

2005

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Section: Relaxation Of High S # 1 Levelssupporting

confidence: 81%

Energy Dissipation in Molecular Systems

Tramer¹,

Jungen²,

Lahmani³

2005

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“…Spectroscopic and photophysical measurements revealed structureless S 1 S 0 absorption band and low quantum yield of fluorescence emission occurring at picoseconds/nanosecond time scale. [147][148][149][150] A biexponential nature of the emission profile is also observed for HFBz. 150 Furthermore, additional absorption band observed in HFBz as compared with Bz and is designated as unassigned C-band.…”

Section: Hexafluorobenzenementioning

confidence: 60%

“…Because of high symmetry many energetically low‐lying electronic states of this molecule are orbitally degenerate and prone to the JT instability. Spectroscopic and photophysical measurements revealed structureless S 1 ← S 0 absorption band and low quantum yield of fluorescence emission occurring at picoseconds/nanosecond time scale 147–150 . A biexponential nature of the emission profile is also observed for HFBz 150 .…”

Section: Representative Examplesmentioning

confidence: 77%

Structure and dynamics of electronically excited molecular systems

Mahapatra

2021

WIREs Comput Mol Sci

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Structure and dynamics of electronic excited states of molecular systems is of contemporary interest to understand a rich variety of processes ranging from molecular spectroscopy to reaction dynamics. Developments over the past decades have established that coupling of electronic and nuclear motion is a generic feature in polyatomic molecular systems which causes a breakdown of the Born-Oppenheimer approximation. Such a coupling leads to conical intersections in non-linear and glancing degeneracy in linear polyatomic systems. While the former case is quite general and has wide variances depending on the nature of the coupling on the symmetry ground, the latter one is specific to the linear systems having axial symmetry. The Jahn-Teller (JT) systems form a subclass in the former category and the latter category constitutes the Renner-Teller (RT) systems. These systems are characterized by high point group symmetry and orbital degeneracy. The latter splits upon distortion along suitable symmetry reducing nuclear displacement. The JT or the RT split component states may undergo symmetry allowed coupling among another JT or RT split component states or with some non-degenerate states. These are termed as the pseudo-JT and pseudo-RT coupling, respectively.We have studied a variety of photo-induced molecular processes with the aid of ab initio quantum chemistry and first principles quantum dynamics methods. We will document here some of the important developments in the field focusing on the work done on the JT and RT systems primarily in our own laboratory.

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“…This trend agrees with the literature reported S1→S0 decay times, where 6 > 1 > 3. [23][24] The decay time of 9 has not yet been reported; our calculations predict that it will be between 1 and 3. The excitedstate lifetimes of fluorobenzenes are longer than 1 picosecond because they quickly locate an S1minimum region near the S1-FC region, where they can radiatively decay.…”

Section: Nn Predicted Excited-state Lifetimes Of Fluorobenzenesmentioning

confidence: 73%

“…[22] It is consistent with the early fluorescence study by Loper et al, where the reported time-constants of 1 and 3 at 254-280 nm were 1.7-3.6 and 1.6-1.7 ns, respectively. [23] Loper explains that the symmetry reduction from D6h in 1 to C2v in 3 favors the electronic transition, thus shortening the excited-state lifetime of 3. The nonradiative S1→S0 decay measured by Studzinski et al showed that the lifetime of 6 was 2.7 times longer than 1.…”

Section: Scheme 1 Photochemical Isomerization Of Benzene and Fluorobenzenesmentioning

confidence: 99%

Excited-state distortions control the reactivities and regioselectivities of photochemical 4π-electrocyclizations of fluorobenzenes

Lopez

2021

Preprint

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The photochemistry of benzene is complex and non-selective because numerous mechanistic pathways are accessible in the ground- and excited-states. Fluorination is a known strategy to increase the chemoselectivities for Dewar-benzenes via 4π-disrotatory electrocyclization. However, the origin of the chemo- and regioselectivities of fluorobenzenes remains unexplained because of experimental limitations in resolving the excited-state structures on ultrafast timescales. The computational cost of multiconfigurational nonadiabatic molecular dynamics simulations is also generally prohibitive. We now provide high-fidelity structural information and reaction outcome predictions with machine-learning-accelerated photodynamics simulations of a series of fluorobenzenes, C6F6-nHn, n=0–3 to study their S1→S0 decay in 4 ns. We trained neural networks with XMS-CASPT2(6,7)/aug-cc-pVDZ calculations, which reproduced the S1 absorption features with mean absolute errors of 0.04 eV (< 2 nm). The predicted S1 excited-state lifetimes for C6F4H2, C6F6, C6F5H, and C6F3H3 are 64, 40, 18, and 8 ps, respectively. The trend is in excellent agreement with the experimental lifetimes. Our calculations show that the pseudo Jahn-Teller distortions create the S1 minimum region that prolongs the excited-state lifetime of fluorobenzenes. The pseudo Jahn-Teller distortions reduce when fluorination decreases. Characterization of the surface hopping structures suggests that the S1 relaxation first involves a cis-trans isomerization of a 𝜋C-C-bond in the benzene ring, promoted by the pseudo-Jahn-Teller distortions. A branching plane analysis revealed that the conical intersections favoring 4π-electrocyclization are less energetically accessible through the S1 relaxation; lower-energy conical intersections resemble the reactant and favor reversion.

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Fluorescence decay and radiative lifetimes of fluorinated aromatic molecules

Cited by 50 publications

References 27 publications

Energy Dissipation in Molecular Systems

Energy Dissipation in Molecular Systems

Structure and dynamics of electronically excited molecular systems

Excited-state distortions control the reactivities and regioselectivities of photochemical 4π-electrocyclizations of fluorobenzenes

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