Conformation of Acyclic Derivatives of 1,1,4,4-Tetraphenyl-1,3-butadiene

Toda, Fumio; Tanaka, K.; Stein, Zafra; Goldberg, Israel

doi:10.1107/s0108270195011358

Cited by 16 publications

(50 citation statements)

References 11 publications

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“…Because of the restriction by this ring (Figure 2), phenyl groups are prevented from free rotation and steric constrain between them cannot be released. 50 To the best of our knowledge, this is the longest C-C covalent bond that has been reported experimentally (some C-C "bondings" around 3 Å have been reported, 51-53 but they are distinguishable from the covalent "bonds" mentioned here). In view of the molecular size, 1 was optimized at the B3LYP/6-311G(d,p) level.…”

Section: Exceptionally Long C-c Covalent Bondsmentioning

confidence: 67%

Two-Center Two-Electron Covalent Bonds with Deficient Bonding Densities

Yang

2012

J. Phys. Chem. A

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Electron-deficient covalent bonds are a type of covalent bonds without electron accumulation at their bonding regions. Compared with normal covalent bonds, they are quite sensitive to chemical environments. Electron-deficient and normal covalent bonds are not isolated from each other. An electron-deficient bond may change to a normal one upon the change of substituting groups. Neither bond elongation nor atom electronegativity is directly related to the electron deficiency in an electron-deficient bond. Atoms in molecules (AIM) analyses suggest that electron-deficient bonds are characterized by positive Laplacians and small ρ(BCP) values. The positive Laplacian is caused by insignificant electron accumulation perpendicular to the bond path. On the basis of electron localization function (ELF) descriptors, electron-deficient bonds have small basin populations, low η values and high relative fluctuations. There may be one or two bond basins for an electron-deficient bond. In addition, such a bond may correlate with two more valence basins close to the two participating atoms. Electron-deficient bonds are usually weak and long. This is consistent with the low s characters in their natural bond orbitals (NBOs).

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Section: Exceptionally Long C-c Covalent Bondsmentioning

confidence: 67%

Two-Center Two-Electron Covalent Bonds with Deficient Bonding Densities

Yang

2012

J. Phys. Chem. A

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“…At the same time, the possibility of unusually long C-C bond lengths has attracted much attention for its challenging nature raising the questions: is there an upper limit to the length of a stretched C-C single bond? Recently, Toda et al 2 have reported unusually long C-C bond lengths such as 1.720(4) Å in 1, and 1.710(5) as well as 1.724(5) Å in 2. They are considered the longest C-C single bonds accurately determined to date.…”

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confidence: 99%

Consistencies between experiments and quantum calculations of strained C–C single bond lengths

Choi¹,

Kertész²

1997

Chem. Commun.

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“…The extraordinary long carbon–carbon bonds are not unknown in organic molecules 11–14. The bond length of 1.781 Å was found by Fritz et al 12 in a disilabicyclobutane.…”

Section: The σAb Square‐root Average Bond Distance Differences For Thmentioning

confidence: 89%

“…The bond length of 1.781 Å was found by Fritz et al 12 in a disilabicyclobutane. Toda et al 13 synthesized two tetraphenylcyclobutarenes, which have bond lengths from 1.710 to 1.724 Å. Kammermeier et al 14 measured long carbon–carbon bonds in dianthracene derivatives. The experimental bond lengths from 1.624 to 1.713 Å were confirmed by Becke3LYP/6‐31G* and PM3 calculations.…”

Section: The σAb Square‐root Average Bond Distance Differences For Thmentioning

confidence: 99%

Toroidal and spherical fullerene‐like molecules with only pentagonal and heptagonal faces

László

Rassat

2001

Int J of Quantum Chemistry

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ABSTRACT:The stability of toroidal and spherical carbon cage structures, constructed from five-and seven-membered rings, was studied using tight binding, Tersoff and Brenner potential based methods. A special tiling is presented for the torus of minimal strain energy. In order to make comparison between the results of various calculations we defined the σ AB square root average bond distance difference between the methods A and B. By addition of six-membered rings to the C 40 torus we obtained a toroidal C 60 carbon cage molecule. Key words: toroidal carbon structures; toroidal azulenoid; fullerene-like molecules S ince the discovery of the C 60 buckminsterfullerene [1], several new carbon structures were found in experimental and theoretical works [2 -5].For a closed carbon network of N 5 pentagons, N 6 hexagons, and N 7 heptagons, when each carbon atom has three neighbors, Euler's theorem gives that where χ is the Euler characteristic and g is the genus. The genus is the number of holes or handles, thus g = 1 for the torus and g = 0 for the sphere. The question arises whether there are closed-cage carbonic networks that do not contain hexagons. In the present work we shall study such kinds of toroidal and spherical carbon structures. From Eq.(1) follows that N 5 = N 7 for the torus and N 5 = N 7 + 12 for the sphere. We calculated the equilibrium structures in the frame work of a molecular mechanics procedure. The carbon-carbon interaction was described with the help of a tight-binding (TB) method [6]. The parameters were adjusted to the results of density functional calculations for graphite, diamond, and other carbon structures. In order to make a com-

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Conformation of Acyclic Derivatives of 1,1,4,4-Tetraphenyl-1,3-butadiene

Cited by 16 publications

References 11 publications

Two-Center Two-Electron Covalent Bonds with Deficient Bonding Densities

Two-Center Two-Electron Covalent Bonds with Deficient Bonding Densities

Consistencies between experiments and quantum calculations of strained C–C single bond lengths

Toroidal and spherical fullerene‐like molecules with only pentagonal and heptagonal faces

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