Effects of solvents and substituents controlling the adiabatic or diabatic modes of the cis → trans isomerization of styrylpyrenes in the excited singlet state

Kikuchi, Yoshihiko; Okamoto, H.; Aral, Tatsuo; Tokumaru, Katsumi

doi:10.1016/0009-2614(94)01071-4

Cited by 16 publications

(7 citation statements)

References 19 publications

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“…There is a red shift (Py1Bz: 378 nm, Py1BzOH: 387 nm, Py1Bz(OH) 2 : 390 nm and Py1SA: 393 nm) for the absorption maxima with a slight loss of vibronic structure indicating weak ICT between the two aromatic moieties. Compared to Py1Bz, which was found to experience no CT in the excited state as seen from the vibronic structure of the emission band in DMSO,, the emission spectra of Py1BzOH, Py1Bz(OH) 2 are red‐shifted with only a slight loss of vibronic structure. Their emissions were almost identical and attributed to the ICT state, demonstrating that the hydroxyl‐group at the para‐position of benzene mainly affects the emission.…”

Section: Resultsmentioning

confidence: 89%

Intramolecular Proton and Charge Transfer of Pyrene‐based trans‐Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins

et al. 2018

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Two analogues to the fluorescent amyloid probe 2,5-bis(4'-hydroxy-3'-carboxy-styryl)benzene (X-34) were synthesized based on the trans-stilbene pyrene scaffold (Py1SA and Py2SA). The compounds show strikingly different emission spectra when bound to preformed Aβ1-42 fibrils. This remarkable emission difference is retained when bound to amyloid fibrils of four distinct proteins, suggesting a common binding configuration for each molecule. Density functional theory calculations show that Py1SA is twisted, while Py2SA is more planar. Still, an analysis of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the two compounds indicates that the degree of electronic coupling between the pyrene and salicylic acid (SA) moieties is larger in Py1SA than in Py2SA. Excited state intramolecular proton transfer (ESIPT) coupled-charge transfer (ICT) was observed for the anionic form in polar solvents. We conclude that ICT properties of trans-stilbene derivatives can be utilized for amyloid probe design with large changes in emission spectra and decay times from analogous chemical structures depending on the detailed physical nature of the binding site.

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Section: Resultsmentioning

confidence: 89%

Intramolecular Proton and Charge Transfer of Pyrene‐based trans‐Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins

et al. 2018

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“…The emission of solutions of the cis isomer was shown to contain substantial contributions of fluorescence from the trans isomer. Other examples followed soon thereafter. − Our work has shown that, as the aryl substituent in cis -ArCH = CHPh derivatives is changed from phenyl (Ph) to 2-naphthyl (2-Np) and then to 2-anthryl (2-An), the efficiency of the adiabatic 1 c* → 1 t* pathway increases from 0.2% to >2% and to >44%, respectively . The greater localization of the electronic excitation in the largest aryl group is reflected in a 1000-fold increase in the fluorescence lifetime of cis -1-(2-anthryl)-2-phenylethene ( c -APE) relative to cis -1-(2-naphthyl)-2-phenylethene ( c -NPE). 8d,e Moreover, the adiabatic photoisomerization pathway in these two molecules is highly conformer specific.…”

Section: Introductionmentioning

confidence: 95%

Temperature Dependence of the Photoisomerization of cis-1-(2-Anthryl)-2-phenylethene. Conformer-Specificity, Torsional Energetics and Mechanism

1997

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Emission from cis-1-(2-anthryl)-2-phenylethene, c-APE*, in toluene is resolved into 1 t-APEB* and 1 c-APE* components at temperatures ranging between 4.3 and 59.3 °C. Decomposition of effective fluorescence quantum yields, φ fc , into pure component fluorescence quantum yields, φ ft -B and φ fc , shows that φ ft -B increases 24% with increasing temperature while φ fc decreases more than 3-fold over this temperature range. On the basis of the fraction of molecules that escape the 1 c-APE* potential energy minimum, 1 − φ fc , the efficiency of adiabatic formation of 1 t-APEB* remains remarkably temperature independent at 50.5 ± 0.7%. These results, together with photoisomerization quantum yields as a function of [c-APE] in degassed and air-saturated toluene, reveal a detailed photoisomerization mechanism. At infinite dilution and in the absence of molecular oxygen, photoisomerization of c-APE occurs predominantly via the adiabatic, conformer-specific 1 c-APEB* → 1 t-APEB* pathway. This torsional motion experiences a 4.44 ± 0.14 kcal/mol barrier probably located at the perpendicular, 3p*, geometry. Since 12% of 1 t-APEB* intersystem cross to 3 t-APEB*, the known triplet state quantum chain process enhances photoisomerization quantum yields at higher [c-APE]. Triplets formed directly from 1 c-APE* also contribute to this pathway. In air-saturated solutions, oxygen eliminates the quantum chain process by reducing the lifetime of 3 t-APE*. However, the quenching of 1 c-APE* by O2 gives 3 c-APE*, thus enhancing photoisomerization quantum yields via rapid 3 c-APE* → 3 t-APE* adiabatic torsional displacement. No photoisomerization of 1 c-APEA* need be postulated to account for our observations. The enthalpy difference between ground state conformers, ΔH AB, favors c-APEB by 0.92 ± 0.02 kcal/mol.

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“…The data for E-1P2QE can be compared with those for E-SP, which does not photoisomerize in the trans → cis direction (ϕ tc ∼0). The lifetime for the E-SP is 5.3 ns (hexane) and φ fl = 0.82; 35 thus, k fl = 1.5 × 10 8 s −1 and k nr = 0.4 × 10 8 s −1 .…”

Section: Resultsmentioning

confidence: 99%

Visible-light-driven two-way photoisomerization of 1-(1-pyrenyl)-2-(2-quinolyl)ethylene in neutral and protonated forms

Будыка

2018

Photochem Photobiol Sci

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Diarylethylenes with large π-systems often lose their photochemical activity (the size effect). 1-(1-Pyrenyl)-2-(2-quinolyl)ethylene (1P2QE), despite having a large conjugated π-system of 28 electrons, undergoes two-way reversible trans-cis photoisomerization both in the neutral and protonated forms with quantum yields as high as 0.13-0.83. For the neutral 1P2QE, experimental data and quantum-chemical calculations indicate a diabatic (nonadiabatic) reaction mechanism. Due to high photoisomerization quantum yields and the long-wavelength absorption band at 340-460 nm and 390-560 nm for the neutral and protonated compounds, respectively, 1P2QE can be used as a molecular photoswitch that is sensitive to visible light.

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Effects of solvents and substituents controlling the adiabatic or diabatic modes of the cis → trans isomerization of styrylpyrenes in the excited singlet state

Cited by 16 publications

References 19 publications

Intramolecular Proton and Charge Transfer of Pyrene‐based trans‐Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins

Intramolecular Proton and Charge Transfer of Pyrene‐based trans‐Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins

Temperature Dependence of the Photoisomerization of cis-1-(2-Anthryl)-2-phenylethene. Conformer-Specificity, Torsional Energetics and Mechanism

Visible-light-driven two-way photoisomerization of 1-(1-pyrenyl)-2-(2-quinolyl)ethylene in neutral and protonated forms

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