Molecules with Labile Bonds: Selected Annulenes and Bridged Homotropilidenes

Williams, Richard Vaughan

doi:10.1002/9783527627134.ch8

Cited by 6 publications

(7 citation statements)

References 171 publications

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“…Cope rearrangements of SBV and several derivatives have already served as touchstones for various properties that are related to pericyclic reactivity, from synthesis 12,16,21,22,29 via spectroscopy 13,15,20,24,27 and kinetics 13,14,19 to electronic structure 17,18,[21][22][23][24][25][26][28][29][30][31]35 and the related thermochromicity, 3,21,22,24,29 ab initio molecular dynamics 32 , the role of tunnelling 33 , and the above-mentioned quantum dynamics simulations of IR pump-dump laser control. [2][3][4] In particular, quantum chemistry first principal calculations show that the Cope rearrangement of SBV in the electronic ground state .)…”

Section: Introductionmentioning

confidence: 99%

“…The labels for the carbon atoms (see product structure P) are the same for R and P. proceeds in a symmetric double well potential energy surface (PES), with two equivalent minima representing R and P which are separated by a rather shallow barrier. 18,21,22,24,26,[28][29][30][31]33 In contrast, in the first excited electronic state, SBV has a rather steep and deep symmetric single well PES with large energy gap to the potential barrier in the electronic ground state ( E 2 eV 18,20,24 ).…”

Section: Introductionmentioning

confidence: 99%

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Optimal control of the initiation of a pericyclic reaction in the electronic ground state#

Bredtmann

Manz

2012

J Chem Sci

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Pericyclic reactions in the electronic ground state may be initiated by down-chirped pump-dump sub-pulses of an optimal laser pulse, in the ultraviolet (UV) frequency and sub-10 femtosecond (fs) time domain. This is demonstrated by means of a quantum dynamics model simulation of the Cope rearrangement of Semibullvalene. The laser pulse is designed by means of optimal control theory, with detailed analysis of the mechanism. The theoretical results support the recent experimental initiation of a pericyclic reaction. The present approach provides an important step towards monitoring asynchronous electronic fluxes during synchronous nuclear pericyclic reaction dynamics, with femto-to-attosecond time resolution, as motivated by the recent prediction of our group.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimal control of the initiation of a pericyclic reaction in the electronic ground state#

Bredtmann

Manz

2012

J Chem Sci

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“…which are again consequences of the periodic time evolution (12) and molecular symmetry. Finally, the reduced nuclear flux density, or flux j Rs,n (Q,t), is illustrated in Figure 2j, again by a contour plot (cf.…”

Section: The Journal Of Physical Chemistry Amentioning

confidence: 84%

“…The general theory of CENFS during tunnelling of systems with asymmetric double-well potentials (Section ) will now be applied to CENFs during a pericyclic reaction, exemplarily, the Cope rearrangement of SBV, ,,− by tunnelling in external electric fields. The presentation will follow the order of Section , i.e., for reference, we shall first show the results for the symmetric system (SBV without external field), followed by those for the asymmetric system (SBV in weak and moderate electric fields.)…”

Section: Applications To Cenfs During Cope Rearrangement Of Semibullv...mentioning

confidence: 99%

“…Both R and P have C s symmetry; accordingly, our model assumes conservation of C s symmetry during the reaction. The importance of tunnelling reactions in organic chemistry has been demonstrated recently. − The example, SBV, and several derivatives have already served as touchstones for various investigations of pericyclic reactivity: synthesis, − spectroscopy, − kinetics, ,, electronic structure, ,,,,− thermochromicity, − ,, ab initio molecular dynamics, quantum dynamics of laser control, ,− and imaging of chemically active valence electrons during a pericyclic reaction . The thermochromicity of SBV, for example, is supported by the rather low potential barrier between R and P and the rather large energy gap between the potential energy surfaces (PES) of the electronic ground and first excited states. ,,,, Hence, the low barrier supports tunnelling in the electronic ground state.…”

Section: Introductionmentioning

confidence: 99%

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Concerted Electronic and Nuclear Fluxes During Coherent Tunnelling in Asymmetric Double-Well Potentials

Bredtmann¹,

Manz

Zhao³

2016

J. Phys. Chem. A

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The quantum theory of concerted electronic and nuclear fluxes (CENFs) during coherent periodic tunnelling from reactants (R) to products (P) and back to R in molecules with asymmetric double-well potentials is developed. The results are deduced from the solution of the time-dependent Schrödinger equation as a coherent superposition of two eigenstates; here, these are the two states of the lowest tunnelling doublet. This allows the periodic time evolutions of the resulting electronic and nuclear probability densities (EPDs and NPDs) as well as the CENFs to be expressed in terms of simple sinusodial functions. These analytical results reveal various phenomena during coherent tunnelling in asymmetric double-well potentials, e.g., all EPDs and NPDs as well as all CENFs are synchronous. Distortion of the symmetric reference to a system with an asymmetric double-well potential breaks the spatial symmetry of the EPDs and NPDs, but, surprisingly, the symmetry of the CENFs is conserved. Exemplary application to the Cope rearrangement of semibullvalene shows that tunnelling of the ideal symmetric system can be suppressed by asymmetries induced by rather small external electric fields. The amplitude for the half tunnelling, half nontunnelling border is as low as 0.218 × 10(-8) V/cm. At the same time, the delocalized eigenstates of the symmetric reference, which can be regarded as Schrödinger's cat-type states representing R and P with equal probabilities, get localized at one or the other minima of the asymmetric double-well potential, representing either R or P.

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4,6‐Barbaralanedicarboxy‐2,8‐dicarboxylic anhydride and 1,5‐dimethyl‐4,6‐semibullvalenedicarboxy‐2,8‐dicarboxylic anhydride: examples of unusual barbaralanes and semibullvalenes that do not undergo the Cope rearrangement. They are locked as the closed tautomers

Williams

Aring

Bonifacio

et al. 2016

J of Physical Organic Chem

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Barbaralanes and semibullvalenes are generally fluxional molecules renowned for their exceedingly low Cope rearrangement activation barriers and their close approach to homoaromaticity. The title compounds are unusual in that they do not undergo the Cope rearrangement and are locked as a single tautomer with no evidence whatsoever for the existence of the other “open” tautomer. This total lack of the Cope rearrangement was demonstrated through variable‐temperature 13C NMR spectroscopy and computational studies. Copyright © 2016 John Wiley & Sons, Ltd.

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Molecules with Labile Bonds: Selected Annulenes and Bridged Homotropilidenes

Cited by 6 publications

References 171 publications

Optimal control of the initiation of a pericyclic reaction in the electronic ground state#

Optimal control of the initiation of a pericyclic reaction in the electronic ground state#

Concerted Electronic and Nuclear Fluxes During Coherent Tunnelling in Asymmetric Double-Well Potentials

4,6‐Barbaralanedicarboxy‐2,8‐dicarboxylic anhydride and 1,5‐dimethyl‐4,6‐semibullvalenedicarboxy‐2,8‐dicarboxylic anhydride: examples of unusual barbaralanes and semibullvalenes that do not undergo the Cope rearrangement. They are locked as the closed tautomers

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