Diradicalar or ionic twisted excited states in the singlet cis-trans isomerization of polyenes?

Nebot–Gil, Ignacio; Malrieu, Jean Paul

doi:10.1021/ja00376a012

Cited by 18 publications

(3 citation statements)

References 5 publications

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“…The importance of this process is illustrated by its presence in a large number of biological systems, for instance the ultrafast cis−trans isomerization in the retinal chromophore of rhodopsin which triggers a series of events ultimately leading to vision in mammals . An overwhelming number of both theoretical − and experimental − studies focusing on the dynamics, lifetimes, and electronic features of these isomerizations in a wide variety of olefins has been performed in order to gain deeper insight in this process.…”

Section: Introductionmentioning

confidence: 99%

Solvent Induced Charge Separation in the Excited States of Symmetrical Ethylene: A Direct Reaction Field Study

et al. 2001

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The polarization of the excited states of near-perpendicularly twisted ethylene in the condensed phase has been investigated by means of direct reaction field (DRF) calculations. In these calculations, five organic solvents with variable polarity and polarizability were simulated by 50 discrete, classically described solvent molecules. The excited states of near-perpendicular ethylene were described by ab initio methods at the CISD level of theory using a DZV basis set. It is demonstrated that there is a distinct correlation between the polarity of the solvent and the occurrence and stabilization of charge separated excited states of ethylene. Large dipole moments were observed for ethylene excited states in polar solvents, indicating that an asymmetric distribution of polar solvent molecules around the ethylene can introduce enough symmetry breaking to cause charge separation. This behavior was not observed for (models of) nonpolar solvents. This charge separation process can be designated as unbiased "sudden polarization" since the solvent shells used were in equilibrium with the nonpolarized ethylene solute.

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Section: Introductionmentioning

confidence: 99%

Solvent Induced Charge Separation in the Excited States of Symmetrical Ethylene: A Direct Reaction Field Study

et al. 2001

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“…The majority of the theoretical studies are concerned with aliphatic systems. Exceptions are two calculations done by Nebot-Gil and ~irieu[40] and Orlandi and coworkers[41] on styrene. The lowest ionic singlet state calculated by Nebot-Gii and Malrieu[40] has the benzyl moiety with the positive charge and the methylene with the negative charge ($4).…”

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confidence: 99%

“…Exceptions are two calculations done by Nebot-Gil and ~irieu[40] and Orlandi and coworkers[41] on styrene. The lowest ionic singlet state calculated by Nebot-Gii and Malrieu[40] has the benzyl moiety with the positive charge and the methylene with the negative charge ($4). Surprisingly, Orlandi and coworkers'[41] results predict the opposite charge distribution for the lowest ionic singlet state.…”

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confidence: 99%

Photogenerated carbonium ions and vinyl cations in aqueous solution

Wan

Yates

1984

Reviews of Chemical Intermediates

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A CASSCF study on the lowest ???* excitation of urocanic acid

Lahti¹,

Hotokka²,

Neuvonen³

et al. 1999

Int. J. Quant. Chem.

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ABSTRACT:The photochemical cisrtrans isomerization of urocanic acid UCA,. . E -3-1 H-imidazol-4 -yl propenoic acid was investigated using complete active space Ž . SCF CASSCF ab initio calculations. The singlet ground state and the triplet and the U Ž . singlet manifolds of the lowest-lying ª HOMO ª LUMO excitation of the neutral and the anionic UCA were calculated using the 6-31G U and the 6-31 q G U basis sets, respectively. The torsional barrier of the double bond of the propenoic acid moiety in UCA is observed to be considerably lower in the T and S excited states of the neutral energy difference is larger in the excited states than in the ground state, probably due to strengthening of the intramolecular hydrogen bond of cis-UCA as the molecule is excited. The results of the calculations, interpreted in terms of the idea that UCA is deprotonated upon electronic excitation, led to construction of a new model for the photoisomerization mechanisms of UCA. According to this model, the trans-to-cis isomerization proceeds via both the triplet and the singlet manifolds in the deprotonated form of UCA. This isomerization may occur in the S state of the neutral UCA as well. The cis-to-trans 0 isomerization is suggested to proceed only in the S state of the neutral UCA. ᮊ 1999

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Diradicalar or ionic twisted excited states in the singlet cis-trans isomerization of polyenes?

Cited by 18 publications

References 5 publications

Solvent Induced Charge Separation in the Excited States of Symmetrical Ethylene: A Direct Reaction Field Study

Solvent Induced Charge Separation in the Excited States of Symmetrical Ethylene: A Direct Reaction Field Study

Photogenerated carbonium ions and vinyl cations in aqueous solution

A CASSCF study on the lowest ???* excitation of urocanic acid

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