The photochemistry of 1,4-cyclohexadiene in solution and in the gas phase: conical intersections and the origin of the ‘helicopter-type’ motion of H2 photo-generated in the isolated molecule

Zilberg, Shmuel; Haas, Yehuda

doi:10.1039/b107991n

Cited by 13 publications

(7 citation statements)

References 27 publications

(67 reference statements)

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“…The use of the Longuet-Higgins phase change theorem 17 for finding conical intersections was recently discussed in detail. [18][19][20][21][22] Conical intersections are located by looking for points surrounded by phase-inverting Longuet-Higgins loops. As a full description can be found in ref.…”

Section: Locating Conical Intersectionsmentioning

confidence: 99%

“…Starting at R, the return from the excited state can lead to the formation of the desired product, P, and another one, S. Indeed, as many photochemical reactions are known to lead to two or more products, this method was shown to properly portray them. [18][19][20][21][22]31 This is a correct model for photochemical reactions going through a conical intersection, in the case of covalent molecules, where each of the three molecules R, P and S is described by a different dominant covalent spin-pairing structure (anchors).…”

Section: Locating Conical Intersectionsmentioning

confidence: 99%

“…The method used here is similar to that described in ref. 21. In the case of the formaldiminium cation, the two transition states are expected to have one common symmetry element-the CH 1 H 2 plane (common C s symmetry).…”

Section: Iiic Finding the Conical Intersectionmentioning

confidence: 99%

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Isomerization around a C=N double bond and a C=C double bond with a nitrogen atom attached: thermal and photochemical routes

Zilberg

Haas

2003

Photochem Photobiol Sci

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The Longuet-Higgins phase change theorem is used to show that, in certain photochemical reactions, a single product is formed via a conical intersection. The cis-trans isomerization around the double bond in the formaldiminium cation and vinylamine are shown to be possible examples. This situation is expected to hold when the reactant can be converted to the product via two distinct elementary ground-state reactions that differ in their phase characteristics. In one, the total electronic wavefunction preserves its phase in the reaction; in the other, the phase is inverted. Under these conditions, a conical intersection necessarily connects the first electronic excited state to the ground state, leading to rapid photochemical isomerization following optical excitation. Detailed quantum chemical calculations support the proposed model. The possibility that a similar mechanism is operative in other systems, among them the rapid photo-induced cis-trans isomerization of longer protonated Schiff bases (the parent chromophores of rhodopsins), is discussed.

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Section: Locating Conical Intersectionsmentioning

confidence: 99%

Section: Locating Conical Intersectionsmentioning

confidence: 99%

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Isomerization around a C=N double bond and a C=C double bond with a nitrogen atom attached: thermal and photochemical routes

Zilberg

Haas

2003

Photochem Photobiol Sci

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“…15,31,34 The photoinduced ring opening (see the horizontal axis in Figure 3.3) of 1,3-cyclohexadiene (CHD) to cZc-hexatriene (HT) [35][36][37][38][39][40][41][42][43][44][45] is a classic photochemical reaction. 15,31,34 The photoinduced ring opening (see the horizontal axis in Figure 3.3) of 1,3-cyclohexadiene (CHD) to cZc-hexatriene (HT) [35][36][37][38][39][40][41][42][43][44][45] is a classic photochemical reaction.…”

Section: Introductionmentioning

confidence: 99%

In This Molecule There Must Be a Conical Intersection

Robb¹

2014

Advances in Physical Organic Chemistry

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“…The arguments of Ref. 1 were used by Zilberg and Haas in a series of subsequent articles 8–16, that treat the properties of aromatic and anti‐aromatic molecules, polyenes, and the appearance of conical intersections. The arguments made in this Comment may be of relevance for the interpretation of these molecular systems as well.…”

Section: Introductionmentioning

confidence: 99%

Comment on “The electron‐pair origin of anti‐aromaticity: Spectroscopic manifestations”

Dufey

2006

Int J of Quantum Chemistry

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ABSTRACT:In the article by Zilberg and Haas, "The Electron-Pair Origin of Anti-aromaticity: Spectroscopic Manifestations," the relative sign of the two Kekulé valence bond functions, R and L, in conjugated cyclic hydrocarbons was discussed. It was proposed that in the ground-state wave function of aromatic compounds, the two functions contribute with like sign, while in the ground state of anti-aromatic compounds, the two functions contribute with opposite sign. In this Comment, it is shown that the two functions enter with like sign also into the ground-state wave function of anti-aromatic compounds. Furthermore, it was argued that resonance tends to (de)stabilize a symmetric ground-state geometry in case of the (anti-)aromatic compounds. The expression derived by Zilberg and Haas for the stabilization energy shows an unusual dependence on the ring size and distortion coordinate. An alternative formula is derived for the stabilization energy, in which the energy depends quadratically on the distortion coordinate. Without further numerical calculations, it is not possible to predict whether this term will (de)stabilize a symmetric geometry of the ground state of (anti-)aromatic molecules. Rather, we are led to believe that the influence of term in question on the geometric stability may be small, thus not providing the main reason for the geometric distortion of anti-aromatic compounds.

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The photochemistry of 1,4-cyclohexadiene in solution and in the gas phase: conical intersections and the origin of the ‘helicopter-type’ motion of H2 photo-generated in the isolated molecule

Cited by 13 publications

References 27 publications

Isomerization around a C=N double bond and a C=C double bond with a nitrogen atom attached: thermal and photochemical routes

Isomerization around a C=N double bond and a C=C double bond with a nitrogen atom attached: thermal and photochemical routes

In This Molecule There Must Be a Conical Intersection

Comment on “The electron‐pair origin of anti‐aromaticity: Spectroscopic manifestations”

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