Differential Medium Effects on the Trans .fwdarw. Cis Photoisomerization of all-trans-1,6-Diphenyl-1,3,5-hexatriene. Competing Diradicaloid vs Zwitterionic Pathways

Saltiel, Jack; Ko, Dong-Hoon; Fleming, Steven A.

doi:10.1021/ja00088a064

Cited by 59 publications

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“…The appearance of EE during the first irradiation times of ZZ indicates the involvement of one photon-two bond isomerization. Similar results of multiple bond isomerization were previously reported for 2,4-hexadiene, 27 cyano-substituted diphenyl-1,3,5-hexatrienes, 28 p-styryl-stilbene, 29 and distyryl-arenes. 30 This process takes place probably through a mechanism involving two consecutive adiabatic processes ( 1 ZZ* f 1 ZE* ( 1 EZ*) f 1 EE* f 1 EE) 29,30 as indicated by the multicomponent emission from the singlet excited intermediates (see Table 3).…”

Section: Ez Ze and Zz Stereoisomers Of 2anphbsupporting

confidence: 88%

Spectral Characterization, Photophysics, and Photochemistry of the Four Stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

et al. 1999

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Using a synthetic strategy, based on retention of stereochemistry in the reagent cinnamaldehyde, the four geometrical isomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene were obtained and chromatographically purified. Their structures were established by optical and nuclear magnetic spectrometry and confirmed by their photochemical behavior. Their excited state properties were investigated by stationary and pulsed fluorimetric techniques and by laser flash photolysis. This paper reports the spectral characterization of the four isomers and the photophysical and photochemical parameters obtained by irradiation in a nonpolar solvent at different temperatures. The important contribution of adiabatic pathways in the photoisomerization mechanism and the role of an upper excited singlet state in the relaxation properties are discussed. Indication of the presence of at least two conformers was obtained only when exciting at the extreme red onset region of the absorption spectrum.

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Section: Ez Ze and Zz Stereoisomers Of 2anphbsupporting

confidence: 88%

Spectral Characterization, Photophysics, and Photochemistry of the Four Stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

et al. 1999

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“…However, starting from ttt-DPH, cct/ctt and cct/tct ratios increase as a function of time as the photostationary states in MCH and AN are established, consistent with ctt-and/or tct-DPH as the primary precursor(s) of cct-DPH. 13 In this work we roughly estimate that, starting from ttt-DPH, initial φ cct values are e0.0003 in MCH. Since at least 15 to 25% of this limiting value can be attributed to photoisomerization via the equilibrated triplet state, 14,22 we conclude that two bond photoisomerization yielding cct-DPH directly from 1 ttt* is, at best, a highly inefficient process.…”

Section: Discussionmentioning

confidence: 71%

“…13 The 20-fold increase in the value of φ ctt S can be compared with a relatively modest 3-fold increase in the value of φ tct S . Differential medium effects on the transition state for terminal vs central bond torsional relaxation are consistent with the proposed zwitterionic electronic distribution for 1 ptt* and diradicaloid character for 1 tpt*.…”

Section: Discussionmentioning

confidence: 99%

“…36 In this solvent also, direct radiationless decay to 1 ttt is the major radiationless decay path, φ nr ) 0.66. 36 Formation of the tct isomer is favored in both solvents in the triplet state 13 and it may be tempting to conclude that this is because twisting about the central bond gives the more stable biradical. 22,37 This conclusion would be incorrect, however, because 3 ptt* and 3 tpt* are transition states and not intermediates …”

Section: Discussionmentioning

confidence: 99%

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Direct Photoisomerization of the 1,6-Diphenyl-1,3,5-hexatrienes. Medium Effect on Triplet and Singlet Contributions

et al. 2000

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Quantum yields for the interconversion of the all- cis,trans,cis,3, in methylcyclohexane (MCH) or acetonitrile (AN) following 366 nm excitation show these processes to be relatively inefficient. Their dependence on the concentration of the DPH reveals significant participation of triplet states in the overall process. Despite very low intersystem crossing quantum yields (0.029 and 0.010 in MCH and AN, respectively) singlet and triplet contributions in the photoisomerization of all-trans-1,6-diphenyl-1,3,5-hexatriene are roughly equal in MCH, and, for the trans,cis,trans isomer, in AN. However, in AN the cis,trans,trans isomer forms nearly exclusively by a singlet pathway from the other two isomers. The cis,cis,trans isomer, a very minor component in photostationary states, appears to form primarily from the cis,trans,trans isomer whose excited singlet state also gives another isomer, tentatively identified as ctc-DPH. The major radiationless channel of the excited singlet state of each DPH isomer is direct decay to the original ground state. Barriers to torsional relaxation of the planar lowest DPH excited singlet states (2 1 A g and 1 1 B u ) must be significantly higher than previously supposed. Photoisomerization quantum yields of all-trans-DPH in the presence of fumaronitrile (FN) are also separated into singlet and triplet contributions. Fumaronitrile quenches DPH fluorescence and singlet contributions to the photoisomerization equally, but enhances DPH triplet formation and the triplet contribution to the photoisomerization. Radical cations of DPH form in AN but do not participate in isomer interconversion.

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“…[9] In addition, SB constitutes an important example of photoinduced trans-cis isomerisation which takes place on the excited singlet-state surface. [10][11][12][13][14][15][16][17] Photoinduced trans-cis isomerisation mechanisms are also operative in the longer a,w-diphenylpolyenes, though with much lower efficiency. [3] Photodetachment photoelectron spectroscopy (PD-PES) on molecular radical anions provides electron affinities and direct spectroscopic access to the lowest triplet states T 1 and T 2 of the corresponding neutral molecules.…”

Section: Introductionmentioning

confidence: 99%

T₁, T₂ State Energies and Electron Affinities of Small α,ω‐Diphenylpolyenes Investigated by Anion Photodetachment Photoelectron Spectroscopy and Excited‐State Theory

et al. 2011

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Photodetachment photoelectron spectroscopy (PD-PES) on molecular radical anions provides electron affinities and direct spectroscopic access to the lowest triplet states T(1) and T(2) of the corresponding neutral molecules. Herein, we apply this method to investigate trans-stilbene (SB), all-trans-1,4-diphenyl-1,3-butadiene (DPB), and all-trans-1,6-diphenyl-1,3,5-hexatriene (DPH). Our gas-phase T(1) energies agree with previous measurements on condensed crystals. The T(2) state energies are determined in this work for the first time. Experimental electron affinities, neutral excited-state transition energies and intensities are compared to theoretical data calculated by using DFT (ground states) or DFT/MRCI (excited states) methods. We give an explanation why intersystem crossing is of minor importance in all three compounds although the T(2) states are situated close below the S1 states.

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Differential Medium Effects on the Trans .fwdarw. Cis Photoisomerization of all-trans-1,6-Diphenyl-1,3,5-hexatriene. Competing Diradicaloid vs Zwitterionic Pathways

Cited by 59 publications

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Spectral Characterization, Photophysics, and Photochemistry of the Four Stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

Spectral Characterization, Photophysics, and Photochemistry of the Four Stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

Direct Photoisomerization of the 1,6-Diphenyl-1,3,5-hexatrienes. Medium Effect on Triplet and Singlet Contributions

T₁, T₂ State Energies and Electron Affinities of Small α,ω‐Diphenylpolyenes Investigated by Anion Photodetachment Photoelectron Spectroscopy and Excited‐State Theory

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Differential Medium Effects on the Trans .fwdarw. Cis Photoisomerization of all-trans-1,6-Diphenyl-1,3,5-hexatriene. Competing Diradicaloid vs Zwitterionic Pathways

Cited by 59 publications

References 0 publications

Spectral Characterization, Photophysics, and Photochemistry of the Four Stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

Spectral Characterization, Photophysics, and Photochemistry of the Four Stereoisomers of 1-(2-anthryl)-4-phenyl-1,3-butadiene

Direct Photoisomerization of the 1,6-Diphenyl-1,3,5-hexatrienes. Medium Effect on Triplet and Singlet Contributions

T1, T2 State Energies and Electron Affinities of Small α,ω‐Diphenylpolyenes Investigated by Anion Photodetachment Photoelectron Spectroscopy and Excited‐State Theory

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T₁, T₂ State Energies and Electron Affinities of Small α,ω‐Diphenylpolyenes Investigated by Anion Photodetachment Photoelectron Spectroscopy and Excited‐State Theory