Time-resolved resonance Raman spectra of trans- and cis-stilbene in the lowest excited triplet state

Langkild̄e, Frans W.; Wilbrandt, R.; Negri, Fabrizia; Orlandi, Giorgio

doi:10.1016/0009-2614(90)87013-h

Cited by 16 publications

(4 citation statements)

References 33 publications

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“…Because the calculated energy for p- 3 is 1.9 kcal/mol below the measured energy, the T 1 PES is slightly underestimated by 2−4 kcal/mol. However, the shape of the T 1 PES at UB3PW91 level is in line with the observation that the Z/E -isomerization of 3 is diabatic, but that it proceeds on a rather flat T 1 surface between E - 3 and p- 3 . ,,− …”

Section: Resultssupporting

confidence: 83%

“…When going from E - 3 to p- 3 the energy gain is 4.1 kcal/mol at the UB3PW91/6-31G(d) level, in agreement with the experiment (1.6−4.5 kcal/mol). , Laser flash photolytic studies by Görner and Schulte-Frohlinde revealed an equilibrium between triplet E - 3 and p- 3 , which implies a flat T 1 PES. Resonance Raman spectroscopy further showed a population of E - 3 in T 1 …”

Section: Resultsmentioning

confidence: 99%

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Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T₁ State

2001

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Nonlocal gradient-corrected and hybrid density functional theory (DFT) have been used to calculate T1 potential energy surfaces (PES), spin densities, and geometries of ethylene and aromatic olefins of various sizes: ethylene (1), styrene (2), stilbene (3), 1,1-diphenylethylene (4), 1,4-bis-(1-propenyl)benzene (5), 1,3-divinylbenzene (6), and 2-(1-propenyl)anthracene (7). Calculated properties were used to determine differences in electronic structure of olefins that follow adiabatic vs diabatic Z/E-isomerization mechanisms. In the planar T1 structure, the CC bond in 1 is elongated to a single bond, but in 7 it remains a double bond, archetypal of excitations in the olefinic bond and in the substituent, respectively. Changes in geometries and spin-density distributions of 2 − 7 reveal that substituent aromaticities vary along the T1 PES. For systems that isomerize diabatically (e.g., 2), substituent aromaticity is regained in the 90° twisted structure of the CC bond (3p*). This leads to stabilization and a minimum on the PES at 3p*. If the substituent of the planar T1 olefin fully can accommodate the triplet biradical and still remain aromatic as in 7, aromaticity is instead reduced upon twist to 3p*, so that the T1 PES has a barrier that is suitable for adiabatic isomerizations. The planar structures of olefins with substituents that are partially antiaromatic in T1 (e.g., phenyl) can be stabilized by radical accepting groups in the proper positions (e.g., 5). In summary, our calculations indicate that for an aryl-substituted olefin the structure with the highest substituent aromaticity in T1 corresponds to the minimum on the T1 PES of Z/E-isomerizations.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T₁ State

2001

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“…For example; Langkilde et al reported that the singlet and triplet excited states of trans-stilbene exhibit similar spectral features in the 1600 cm -1 , aromatic region. [46] Our results show that the carbon triple bond, although weakened, persists in both the excited singlet and triplet states of 4. …”

Section: Triplet State Studiesmentioning

confidence: 84%

A photophysical study of substituted arylethynylenes

et al. 2008

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A study of a group of compounds based on the 1,4-bis(phenylethynyl)benzene (1) architecture was undertaken to improve our understanding of their photophysics and the factors which control their geometry and hence the π-conjugation pathway in the ground and excited state of these compounds. 1 exists as a range of molecular rotamers in the ground state, resulting from the low barrier to rotation around their C(sp)-C(sp2) bonds. These compounds are highly conjugated systems with good electron conducting properties, due to delocalisation of the HOMO and LUMO over the molecule. In the electronic excited state they are capable changing their molecular conformation and will adopt a planar, or near planar, low energy conformation prior to fluorescence emission in solution. In a glassy matrix at 77 K with sterically hindering substituents on the benzene rings of 1, emission form high and low energy conformations are observed. 1 is highly emissive owing to the high oscillator strength of the S 1 →S 0 transition. All the compounds studied maintained their C≡C character in the excited singlet and triplet states. The substitution of the central benzene ring in 1 with a thiophene moiety increases the singlet oxygen generation quantum yield, which is consistent with greater intersystem crossing to the triplet excited state.

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“…Для иден тификации промежуточных короткоживущих структур, а вместе с тем и ха рактера самого фотолиза весьма важную информацию дал метод спектроско пии резонансвого СКР с временным разрешением. Авторам [45], в частности, удалось получить спектры цис и транс изомеров триплетных молекул. Из сопоставления с экспериментальными и теоретическими данными, известны ми из предшествующей литературы, сделан вывод, что молекулы стильбена в этом состоянии имеют плоскую (или почти плоскую) структуру в транс ге ометрии.…”

Section: короткоживущие электронно колебательные системыunclassified

Recent progress in dynamical spectroscopy of Raman light scattering

Bobovich¹

1992

Usp. Fiz. Nauk

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Time-resolved resonance Raman spectra of trans- and cis-stilbene in the lowest excited triplet state

Cited by 16 publications

References 33 publications

Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T₁ State

Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T₁ State

A photophysical study of substituted arylethynylenes

Recent progress in dynamical spectroscopy of Raman light scattering

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Time-resolved resonance Raman spectra of trans- and cis-stilbene in the lowest excited triplet state

Cited by 16 publications

References 33 publications

Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T1 State

Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T1 State

A photophysical study of substituted arylethynylenes

Recent progress in dynamical spectroscopy of Raman light scattering

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Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T₁ State

Characteristics of the Electronic Structures of Diabatically and Adiabatically Z/E-Isomerizing Olefins in the T₁ State