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A valence bond description of the prefulvene extended conical intersection seam of benzene

The permutational isomers of the prefulvene-like minimum energy conical intersection lie on an extended conical intersection seam, where they are connected by higher symmetry structures. Here, we present a VB analysis of the electronic states involved along this extended seam. The VB method produces a spin-exchange density (ie. a bonding pattern) that provides the basis to assign resonance structures to the states. The results show that in the high symmetry region of the seam, the character of the states is dominated by the positive and negative combination of the Kekulé structures, (A+B) and (A-B). The low energy parts of the seam, comprised of lower symmetry conical intersection structures, are stabilized by mixing with the Dewar resonance structures. This feature is responsible for the stability of the benzvalene-like conical intersections. The validity of the VB model is confirmed by calculating the branching space vectors at this level of theory, which are in good agreement with the CASSCF calculated vectors. The VB analysis has also allowed us to complete our picture of the global seam, since it has provided the clue to locate a conical intersection saddle point that interconverts two minima of the prefulvene conical intersection where the carbon bent out of the plane is inverted and rotated by 60°. This saddle point has a benzvalene-like geometry, in agreement with the VB picture

We thank Q. Li for help with the CASSCF computations. This work has been supported by grants CTQ2011-26573 from the Spanish Ministerio de Economia y Competividad, SGR0528 from the Catalan Agencia de Gestio d’Ajuts Universitaris i de Recerca (AGAUR), UNGI08-4E-003 from the Spanish Ministerio de Ciencia e Innovacion and the FEDER fund (European Fund for Regional Development), and the Xarxa de Referencia en Quimica Teorica i Computacional de Catalunya from AGAUR. M.A.R. acknowledges a travel grant from AGAUR (2010PIV00086)

© Journal of Chemical Theory and Computation, 2012, vol. 8, núm. 12, p. 4922-4930

American Chemical Society (ACS)

Author: Blancafort San José, Lluís
Robb, Michael A.
Date: 2012
Abstract: The permutational isomers of the prefulvene-like minimum energy conical intersection lie on an extended conical intersection seam, where they are connected by higher symmetry structures. Here, we present a VB analysis of the electronic states involved along this extended seam. The VB method produces a spin-exchange density (ie. a bonding pattern) that provides the basis to assign resonance structures to the states. The results show that in the high symmetry region of the seam, the character of the states is dominated by the positive and negative combination of the Kekulé structures, (A+B) and (A-B). The low energy parts of the seam, comprised of lower symmetry conical intersection structures, are stabilized by mixing with the Dewar resonance structures. This feature is responsible for the stability of the benzvalene-like conical intersections. The validity of the VB model is confirmed by calculating the branching space vectors at this level of theory, which are in good agreement with the CASSCF calculated vectors. The VB analysis has also allowed us to complete our picture of the global seam, since it has provided the clue to locate a conical intersection saddle point that interconverts two minima of the prefulvene conical intersection where the carbon bent out of the plane is inverted and rotated by 60°. This saddle point has a benzvalene-like geometry, in agreement with the VB picture
We thank Q. Li for help with the CASSCF computations. This work has been supported by grants CTQ2011-26573 from the Spanish Ministerio de Economia y Competividad, SGR0528 from the Catalan Agencia de Gestio d’Ajuts Universitaris i de Recerca (AGAUR), UNGI08-4E-003 from the Spanish Ministerio de Ciencia e Innovacion and the FEDER fund (European Fund for Regional Development), and the Xarxa de Referencia en Quimica Teorica i Computacional de Catalunya from AGAUR. M.A.R. acknowledges a travel grant from AGAUR (2010PIV00086)
Format: application/pdf
ISSN: 1549-9618 (versió paper)
1549-9626 (versió electrònica)
Document access: http://hdl.handle.net/10256/11478
Language: eng
Publisher: American Chemical Society (ACS)
Collection: MICINN/PN 2012-2014/CTQ2011-26573
MEC/2008/UNGI08-4E-003
AGAUR/2009-2014/2009 SGR-528
AGAUR/2011/2010 PIV 00086
Reproducció digital del document publicat a: http://dx.doi.org/10.1021/ct300625u
Articles publicats (D-Q)
Is part of: © Journal of Chemical Theory and Computation, 2012, vol. 8, núm. 12, p. 4922-4930
Rights: Tots els drets reservats
Subject: Química de l’estat excitat
Excited state chemistry
Fotoquímica orgànica
Organic photochemistry
Espectroscòpia fotoelèctrica
Photoelectron spectroscopy
Dinàmica molecular
Molecular dynamics
València (Química teòrica)
Valence (Theoretical chemistry)
Benzè -- Estructura
Benzene -- Structure
Title: A valence bond description of the prefulvene extended conical intersection seam of benzene
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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