Next‐generation quantum theory of atoms in molecules for the ground and excited states of fulvene

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The eigenvectors of the electronic stress tensor have been identified as useful for the prediction of chemical reactivity because they determine the most preferred directions to move the bonds.A new 3-D vector based interpretation of the chemical bond that we refer to as the bond-path framework set B provides a version of the quantum theory of atoms in molecules (QTAIM) beyond the minimum definition for bonding that is particularly suitable for understanding changes in molecular electronic structure that occur during reactions. We demonstrate that the most preferred direction for bond motion using the stress tensor corresponds to the most compressible direction and not to the least compressible direction as previously reported. We show the necessity for a directional approach constructed using the eigenvectors along the entire bond-length and demonstrate the insufficiency of scalar measures for capturing the nature of the stress tensor within the QTAIM partitioning. K E Y W O R D Sbond-path framework set, QTAIM, stress tensor, torsion

Section: Theory and Methodsmentioning

confidence: 77%

Stress tensor eigenvector following with next‐generation quantum theory of atoms in molecules

Huang

et al. 2018

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“…In this investigation we suggest the involvement of the e 3 eigenvector also, in the form of a bond‐path twist because earlier it was observed during calculations of the e 1 and e 2 eigenvectors at successive points along the bond‐path that in some cases, these eigenvectors, both being perpendicular to the bond‐path tracing eigenvector e 3 , “switched places”. We recently observed that the calculation of the vector tip path following the unscaled e 1 eigenvector would then show a large “jump” as it swapped directions with the corresponding e 2 eigenvector . This phenomenon indicated a location where the ellipticity ε = 0 due to degeneracies in the corresponding λ 1 and λ 2 eigenvalues, see the Supporting Information S4 for a discussion on the choice of the ellipticity ε as the scaling factor.…”

Section: Theory and Methodsmentioning

confidence: 99%

“…Previously, we considered the S 0 and S 1 electronic states of fulvene for the bond‐path framework set B = {( p 0 , p 1 ),( q 0 , q 1 ), r } …”

Section: Theory and Methodsmentioning

confidence: 99%

“…In this work, we shall investigate the ring‐opening of the CHD along the MEPs in the S 0 and S 1 electronic states and analyze the resultant wave‐functions with next‐generation QTAIM that includes the bond‐path framework set B = { p , q , r } , see Scheme . Recently, the bond‐path framework set B was used to investigate the S 0 and S 1 electronic states of fulvene …”

Section: Introductionmentioning

confidence: 99%

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Next‐generation quantum theory of atoms in molecules for the ground and excited state of the ring‐opening of cyclohexadiene

Tian

Kirk

et al. 2018

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The factors underlying the experimentally observed branching ratio (70:30) of the (1,3‐cyclohexadiene) CHD → HT (1,3,5‐hexatriene) photochemical ring‐opening reaction are investigated. The ring‐opening reaction path is optimized by a high‐level multi‐reference DFT method and the density along the path is analyzed by the quantum theory of atoms in molecules (QTAIM) and stress tensor methods. The performed density analysis suggests that, in both S1 and S0 electronic states, there exists an attractive interaction between the ends of the fissile σ‐bond of CHD that steers the ring‐opening reaction predominantly in the direction of restoration of the ring. It is suggested that opening of the ring and formation of the reaction product (HT) can only be achieved when there is a sufficient persistent nuclear momentum in the direction of stretching of the fissile bond. As this orientation of the nuclear momentum vector can be expected relatively rare during the dynamics, this explains the observed low quantum yield of the ring‐opening reaction.

“…In this investigation we will use the recently introduced “next‐generation” quantum theory of atoms in molecules (QTAIM) to analyze the double bond isomerization of PSB3 in the S 0 and S 1 states. The minimum energy pathways (MEPs) corresponding to each individual torsion θ will be optimized using the state‐interaction state‐averaged spin‐restricted ensemble‐referenced Kohn‐Sham method (SI‐SA‐REKS, or SSR, for brevity).…”

Section: Introductionmentioning

confidence: 99%

A 3‐D bonding perspective of the factors influencing the relative stability of the S₁/S₀ conical intersections of the penta‐2,4‐dieniminium cation (PSB3)

Xin

Momen

et al. 2019

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A balanced treatment of the covalent and ionic contributions to the ground and excited states originating from torsion about double bonds is known to be strongly dependent on the presence of dynamic electron correlation. We undertake an analysis of the minimum energy pathways corresponding to deactivation of the first excited singlet state of PSB3. In doing so we consider torsion about the three double bonds including other intramolecular degrees of freedom, such as the bond length alternation. The 3‐D bond‐path analysis provides a new ‘bond‐localized orbital‐like’ directional interpretation of bonding. Therefore, we present a more sophisticated method of determination of the degree of covalent and ionic contributions known to be responsible for altering the relative stability of the S1/S0 conical intersections. The results presented suggest that the commonly used simplified multi‐reference methodologies that often result in incorrect predictions for the excited state deactivation reaction mechanism.