Aromaticity of bent benzene rings: A VBSCF study

Dijkstra, Fokke; Lenthe, Joop H. van

doi:10.1002/(sici)1097-461x(1999)74:2<213::aid-qua16>3.0.co;2-7

Cited by 39 publications

(35 citation statements)

References 30 publications

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“…Previous VB studies of bent benzenes showed that the description of the π system does not change much for bending angles up to 50°. 23 Thus the VB results obtained for the planar transition state are expected not to deviate much from those of bowl-shaped 7. In addition, the calculation on planar 7 is computationally much cheaper.…”

Section: Methodsmentioning

confidence: 90%

Aromaticity of Pyrene and Its Cyclopentafused CongenersResonance and NICS Criteria. An Ab Initio Valence Bond Analysis in Terms of Kekulé Resonance Structures

et al. 2001

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The effect of cyclopentafusion on the aromatic properties of pyrene and its cyclopentafused congeners has been studied by calculating resonance energies, using the valence bond (VB) method, and nucleus independent chemical shifts using DIGLO. The VB resonance energy is only slightly affected by cyclopentafusion. The resonance interactions between Kekulé resonance structures that lead to six π electron (benzene-like) conjugated circuits have the largest contributions to the resonance energy, in favor of Clar's model. For all compounds these contributions are of similar magnitude. Hence, according to the resonance criterion, all compounds have the same aromatic character. In contrast, the total NICS values show a decrease of aromatic character of the compounds in the series upon the addition of externally fused five-membered rings. However, in line with the resonance criterion, the diamagnetic part of the shielding tensor perpendicular to the molecular framework is nearly constant for all compounds, provided that comparable gauge origins are chosen. Thus, care should be taken by comparing the aromatic character of rings of different molecules by considering only their total NICS values.

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Section: Methodsmentioning

confidence: 90%

Aromaticity of Pyrene and Its Cyclopentafused CongenersResonance and NICS Criteria. An Ab Initio Valence Bond Analysis in Terms of Kekulé Resonance Structures

et al. 2001

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“…Since an aromatic structure is not easily destroyed by bending (cf. Section (5.2), [69]), the VB results obtained for the planar transition state are expected not to deviate much from those of bowl-shaped 7. Of course, the calculation on planar 7 is computationally much cheaper.…”

Section: Aromaticity Of Pyrene and Its Cyclopentafused Congeners [6587]mentioning

confidence: 94%

“…4) were not taken into account. Earlier calculations [52,69] showed that they have a weight of about 6-7% each. Because these weights are relatively small, compared to the total weight of the Kekulé structures of about 80%, and since they obscure the view of the resonance, they were left out.…”

Section: The Importance Of Resonance -Benzene and Cyclobutadiene[246mentioning

confidence: 99%

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TURTLE – A gradient VBSCF Program Theory and Studies of Aromaticity

Lenthe¹,

Dijkstra²,

Havenith³

2002

Theoretical and Computational Chemistry

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The Ab Initio Valence Bond program TURTLE has been under development for about 12 years and is now becoming useful for the non-specialist computational chemist as is exemplified by its incorporation in the GAMESS-UK program. We describe here the principles of the matrix evaluation and orbital optimisation algorithms and the extensions required to use the Valence Bond wavefunctions in analytical (nuclear) gradient calculations. For the applications, the emphasis is on the selective use of restrictions on the orbitals in the Valence Bond wavefunctions, to investigate chemical concepts, in particular resonance in aromatic systems.

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“…Benzene is among the most studied systems in chemistry. This emblematic molecule is an annulene composed of 6 carbon atoms displaced on a D 6h symmetric planar ring, and its geometric, electronic and magnetic properties are still reasons for scientific inquiry . From the energetic point of view, the molecule is more stable than their cyclic polyenes analogues.…”

Section: Many Electron Chemical Bondsmentioning

confidence: 99%

The Nature of the Chemical Bond from a Quantum Mechanical Interference Perspective

2017

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The analysis of the chemical bond in a variety of systems exhibiting distinct bonding patterns was performed using the Generalized Product Function Energy Partitioning (GPF‐EP) approach in order to verify the role played by quantum interference. Diatomic and polyatomic molecules, with single, double and triple bonds, with different degrees of polarity, linear or branched, cyclic or not, conjugated and aromatics, have been considered. In all cases the conclusion was exactly the same: for each bond of the molecule the energy partitioning results showed that the main contribution to the depth of the potential wells comes from the interference term. From the quantum interference perspective the minimum requirement for a chemical bond to be formed is one electron and two interfering one‐electron states belonging to different atoms. As a consequence, all chemical bonds are covalent in the sense that it takes a one‐electron state of each atom to form the bond, irrespective of its polarity.

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Aromaticity of bent benzene rings: A VBSCF study

Cited by 39 publications

References 30 publications

Aromaticity of Pyrene and Its Cyclopentafused CongenersResonance and NICS Criteria. An Ab Initio Valence Bond Analysis in Terms of Kekulé Resonance Structures

Aromaticity of Pyrene and Its Cyclopentafused CongenersResonance and NICS Criteria. An Ab Initio Valence Bond Analysis in Terms of Kekulé Resonance Structures

TURTLE – A gradient VBSCF Program Theory and Studies of Aromaticity

The Nature of the Chemical Bond from a Quantum Mechanical Interference Perspective

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