Photochemical production of non-equilibrium conformer concentrations in glassy solutions of diarylethylenes at 77 K

Алфимов, М. В.; Разумов, В. Ф.; Rachinsky, A.G.; Listvan, V. N.; Scheck, Yu.B.

doi:10.1016/0009-2614(83)87039-0

Cited by 51 publications

(38 citation statements)

References 11 publications

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“…In fact, in many diarylethylenes, the photoisomerization becomes exclusively cis to trans in frozen media. [16] In reporting such stereospecific photoisomerizations, Alfimov [17] and Fischer [18] further noted the formation of unstable conformer(s) of the trans product. Thus, a photochemical entry to the unstable conformers of the product isomer was discovered.…”

Section: Conformer-specific Isomerization Of Diarylethylenesmentioning

confidence: 99%

Examples of Hula-Twist in Photochemicalcis-trans Isomerization

Liu

Hammond²

2001

Chem. Eur. J.

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ALiu and Hammond recently reasoned that the hula-twist (HT), a volume-conserving cis-trans isomerization mechanism, is involved in reactions of confined systems. We now show that HT can be applied to various reported photochemical isomerization of chromophores (small organic systems as well as photoactive bio-pigments). The results, when taken as a whole, argue powerfully that HT is a common supramolecular photoisomerization reaction mechanism.

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Section: Conformer-specific Isomerization Of Diarylethylenesmentioning

confidence: 99%

Examples of Hula-Twist in Photochemicalcis-trans Isomerization

Liu

Hammond²

2001

Chem. Eur. J.

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“…Fuss et al fi rst demonstrated the successful usage of an organic glass at liquid nitrogen temperature in trapping the HT products during irradiation of pre -vitamin D. 8 In reality, their work was preceded two decades ago by those of Alfi mov et al 14 and Castel and Fisher 15 who studied independently photochemical reactions of cis -diarylethylenes in organic glasses. The general conclusion then was that the method was a useful condition for the preparation of conformationally unstable trans products.…”

Section: Trapping the Metastable Ht Productmentioning

confidence: 99%

“…14,15 The extensive list of compounds studied by these two research groups included, for example, naphthyl derivatives ( 9a,b ), anthryl derivatives ( 10 ), and phenanthryl derivatives ( 11 ). 9a 9b 10 11 With the HT mechanism in mind, the Hawaii group recently designed several new systems in a more systematic study.…”

Section: 2 -Diarylethenesmentioning

confidence: 99%

“…Conformational reorganization is a rapid process, for example, the activation energy of reaction of 2 -S -cis -octatetraene to the relaxed all -trans form being 4.0 ± 0.2 kcal mol − 1 (reacting rapidly at > 50 K). 13 But successful trapping of high -energy conformers in rigid media had been amply described: for example, S -cis -1,3 -butadiene in argon matrix 21 and 2 -S -cis -1,3,5,7 -octatetraene in n -octane crystal at < 20 K 23 and high -energy conformers of aryl alkenes 13,14 and trienes 8 in organic glasses at liquid N 2 temperatures. The difference in the observed photochemistry of 19 in EM and iso hexane now becomes very understandable.…”

Section: Organic Glassesmentioning

confidence: 99%

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Supramolecular Effects on Mechanisms of Photoisomerization: Hula Twist, Bicycle Pedal, and One‐Bond‐Flip

Liu

Yang

Zhao

et al. 2011

Supramolecular Photochemistry

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Photoisomerization in the form of interconversion of the cis and trans isomers around a double bond is the key triggering process for many photosensitive biopigments. 1 They include the visual pigment rhodopsin, the proton pumping bacteriorhodopsin (bR), the phototaxis of photoactive yellow protein (PYP), the seed -germinating trigger protein phytochrome, and many other related pigments. Much spectroscopic and chemical effort has gone into elucidation of the primary processes and products associated with these important pigments. These efforts along with photochemical and theoretical work with simple organic systems 2 have led to improved understanding of mechanisms of photoisomerization, often controlled by host molecules in dictating the exact mechanism participating in a given system. In this chapter, an attempt is made to review medium -controlled photoisomerization processes and to provide an overview of different types of mechanisms that take place in nature and under laboratory conditions. Ever since the fi rst picosecond time -resolved spectroscopic study on events revealing the rapid isomerization following photoexcitation of the visual 547 547 Supramolecular Photochemistry: Controlling Photochemical Processes, First Edition. Edited by V. Ramamurthy and Yoshihisa Inoue.

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“…Experimental observation and calculations by Spangler et al 25 have provided compelling evidence that this line may in fact involve two quanta of the v36 or v37 modes whose calculated values in the S1 state were found to be 34. 8 Molecular Geometry of Di2PE in the Crystal. The molecular geometry of Di2PE, as derived from X-ray diffraction at room temperature, is shown in Figure 6.…”

Section: Nature Of the Electronic State Simentioning

confidence: 99%

Shpolskii Spectra of trans-1,2-Di(2'-pyridyl)ethylene. Identification and Evidence for Almost Planar Structure and .pi. Type HMO for the Trapped Rotamer

Tachon¹,

Davies²,

Lamotte³

et al. 1994

J. Phys. Chem.

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The resolved absorption, fluorescence excitation, and fluorescence spectra of trans-stilbene (t-St) and trans-1,2-di(2'-pyridyl)ethylene (Di2PE) in polycrystalline n-Cs and n-Cg matrices at 5 K as well as their geometry in the crystal and potential energy curves along the Ca(ehylefic)-aTyl torsional coordinate have been investigated giving us the opportunity to compare two diarylethylene systems: one in which the Ha(e*ylefic)-Haryl repulsion is on and one in which this interaction is off. In the case of t-St, some lines previously not observed in matrices were assigned to transitions involving two quanta of the C,-phenyl torsion mode (137) of a, symmetry in CZh. We can conclude that in the n-alkane lattice, the t-St molecule tends to be twisted around the C,-phenyl bonds and that its symmetry is either CU, or Ci, as in the pure crystal. The vibronic structures of the sharp line excitation and fluorescence spectra of Di2PE are almost identical to those of t-St except for a slightly lower activity of the in-plane Ca=C,y-Phenyl bending mode (~2 5 ) and Ca=Ca, stretching mode (~7 ) .These results lead us to the conclusion that only one rotamer of Di2PE is trapped in n-C6 and in n-C8. It is characterized by (i) a first electronic transition of marked mc* character with no clear evidence for a contribution from the nonbonding electrons localized on the intracyclic nitrogen atoms and (ii) a conformation similar to that of t-St, with C2h or Ci symmetry. Ah41 computation of the ground-state potential energy curves along the torsional coordinate (Ca-wl) suggest, in the case of t-St, the existence of a very shallow potential barrier to planarity (0.12 kcaYmol) with an equilibrium value for the torsional angle smaller than 20" (Ci symmetry).In the case of Di2PE, these calculations confirm the existence of two minima in the potential curve. The rotamer in which the H3-Ha. repulsion is relieved is found to be the most stable, in agreement with the X-ray diffraction results. Compared to the other rotamer, it is characterized by a more shallow potential around the equilibrium and a smaller barrier to planarity. It has been identified with the rotamer trapped in the n-alkane matrices.

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Photochemical production of non-equilibrium conformer concentrations in glassy solutions of diarylethylenes at 77 K

Cited by 51 publications

References 11 publications

Examples of Hula-Twist in Photochemicalcis-trans Isomerization

Examples of Hula-Twist in Photochemicalcis-trans Isomerization

Supramolecular Effects on Mechanisms of Photoisomerization: Hula Twist, Bicycle Pedal, and One‐Bond‐Flip

Shpolskii Spectra of trans-1,2-Di(2'-pyridyl)ethylene. Identification and Evidence for Almost Planar Structure and .pi. Type HMO for the Trapped Rotamer

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