A global picture of the S1/S0 conical intersection seam of benzene

Li, Quan-Song; Mendive-Tapia, David; Paterson, Martin J.; Migani, Annapaola; Bearpark, Michael J.; Robb, Michael A.; Blancafort, Lluı́s

doi:10.1016/j.chemphys.2010.08.016

Cited by 70 publications

(87 citation statements)

References 37 publications

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“…The presence of the newly found second boat‐type S 2 minimum, lying energetically in between the other two minima however opens possibly new photophysical and photochemical pathways to be considered. As in the case of the S 1 PES of benzene where several boat‐type S 1 /S 0 Conical Intersections (CoIns) have been mapped, we have also found an S 2 /S 1 CoIn (Figure ) which can be accessed from all three minima (see the SI for further details).…”

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confidence: 69%

On the Problem of Multiple Minima on the S2 Excited Potential Energy Surface of Benzene: A Restricted Active Space Self Consistent Field Study

2020

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Application of the Restricted Active Space Self‐Consistent Field Theory on the S2 excited state potential energy surface of benzene shows the existence of three minima. Of these, the first one is planar with a D6h molecular point group, while the other two have a boat type structure with an approximate C2v symmetry. All three minima have a biradicaloid structure and constitute potential candidates for new photochemical pathways on the S2 surface. A common S2/S1 Conical Intersection, which is accessible from all three S2 minima has been found which decays to the S1 potential energy surface (PES) giving benzene S1 minimum as the only photoproduct.

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Section: Figuresupporting

confidence: 69%

On the Problem of Multiple Minima on the S2 Excited Potential Energy Surface of Benzene: A Restricted Active Space Self Consistent Field Study

2020

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“…Accordingly, in other work, our strategy was to determine the complete space of S 0 /S 1 conical intersections for benzene 4,74 and to analyze the computed conical intersection structures obtained at the ab initio level using the MMVB method. However, it does get increasingly rather complicated.…”

Section: Understanding 6 Orbitals With 6 Electrons Conical Intersectimentioning

confidence: 99%

“…69 The reaction path X 3 corresponds to the out-of-plane bending of one CH group. 3,4,74 Here we will focus on just the prefulvene part. The other coordinate in the branching space corresponds to an asymmetric skeletal deformation (which would transform one localized Kekulé structure to another).…”

Section: Understanding 6 Orbitals With 6 Electrons Conical Intersectimentioning

confidence: 99%

In This Molecule There Must Be a Conical Intersection

Robb¹

2014

Advances in Physical Organic Chemistry

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“…In benzene. for example, there are two independent branches on the S 1 /S 0 seam, which consists of at least 13 CI critical points 40 . A given point on a conical intersection seam is always associated with two diabatic electronic states, which are in turn associated with distinct VB structures or combinations of VB structures 1,[41][42][43] .…”

Section: Conceptual Reviewmentioning

confidence: 99%

How the Conical Intersection Seam Controls Chemical Selectivity in the Photocycloaddition of Ethylene and Benzene

et al. 2012

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The photocycloaddition reaction of benzene with ethylene has been studied at the CASSCF level, including the characterization of an extended conical intersection seam. We show that the regioselectivity is, in part, controlled by this extended conical intersection seam and that the shape of the conical intersection seam can be understood in terms of simple VB arguments. Further, the shape and energetics of the asynchronous segment of the conical intersection seam, suggests that 1,2 (ortho) and 1,3 (meta) will be the preferred regioselectivities with similar weight. The 1,4 (para) point on the conical intersection is higher in energy and corresponds to a local maximum on the seam. VB analysis shows that the pairs of VB structures along this asynchronous seam are the same and thus the shape will be determined mainly by steric effects. Synchronous structures on the seam are higher in energy and belong to a different branch of the seam separated by a saddle point on the seam. On S 1 we have documented three mechanistic pathways corresponding to transition states (with low barriers) between the reactants and the conical intersection seam: a mixed asynchronous/synchronous [1,2] ortho path, an asynchronous [1,3] meta path and a synchronous [1,3] meta path. 2 I IntroductionIn general, a photochemical reaction path has two branches: a branch on the excited state and a branch on the ground state. The two branches are connected at a point where the potential energy surfaces become degenerate known as a conical intersection (CI) [1][2][3][4][5][6][7] . However, a conical intersection is not an isolated point, but a collection of points, which we will refer to as a conical intersection "seam" 1,[8][9][10] . In this work we shall explore this feature in some depth for the case of the photochemical reactivity of ethylene and benzene. In the photocycloaddition of an arene and an alkene there are several possible regioselectivities (Scheme I). We will show that this regioselectivity is in part controlled by such an extended conical intersection seam.Experimental Background: Cycloadditions with alkenes are important and characteristic photochemical reactions of aromatic compounds. The prototype example of such a photocycloaddition is the reaction of benzene with ethylene [11][12][13][14][15][16][17][18][19][20][21][22] . Three cycloaddition modes (regioselectivity) can be distinguished (See Scheme 1): ortho-cycloaddition [1,2], meta-cycloaddition [1,3], and para-cycloaddition [1,4], and many applications of these reactions in organic synthesis have been described, as they afford the possibility to obtain polycyclic compounds in one step, which is important in the design of more complex molecular frameworks. Scheme 1 3The photocycloaddition reactions of arenes with alkenes have been extensively studied in order to rationalize the formation of the three possible cycloaddition products 11,16 . The meta-cycloaddition mode ([1,3] in our simplified notation) has been applied most extensively and is used as an important step in ...

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A global picture of the S1/S0 conical intersection seam of benzene

Cited by 70 publications

References 37 publications

On the Problem of Multiple Minima on the S2 Excited Potential Energy Surface of Benzene: A Restricted Active Space Self Consistent Field Study

On the Problem of Multiple Minima on the S2 Excited Potential Energy Surface of Benzene: A Restricted Active Space Self Consistent Field Study

In This Molecule There Must Be a Conical Intersection

How the Conical Intersection Seam Controls Chemical Selectivity in the Photocycloaddition of Ethylene and Benzene

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