Structure and conformation of substituted cycloheptatrienes. I. 2,5-Dimethyl-3,4-diphenyl-1,3,5-cycloheptatriene

Stegemann, Jürgen; Lindner, Hans Jörg

doi:10.1107/s0567740879008657

Cited by 10 publications

(5 citation statements)

References 7 publications

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“…The seven-membered ring has the shape of a shallow boat as shown by a small dihedral angle [35.0(6)°] between planes C1C7C6 and C2C3C4C5. Corresponding dihedral angles in cycloheptatriene derivatives are much larger [for example, 93.1° for 2,5-dimethyl-3,4-diphenyl-1,3,5-cycloheptatriene and 98.3° for 3-anilino-2-(2,4,6-cycloheptatrien-1-yl)-2-propenal] . This difference in dihedral angle values is presumably caused by significant sp character at the alkyne carbons of 3 which increases bond angles C7C1C2 [134.7(5)°] and C1C2C3 [134.4(4)°].…”

Section: Resultsmentioning

confidence: 99%

Bis(triphenylphosphine)palladium Cycloheptadienynylium Tetrafluoroborate: A Palladium Complex of Tropyne

1996

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Section: Resultsmentioning

confidence: 99%

Bis(triphenylphosphine)palladium Cycloheptadienynylium Tetrafluoroborate: A Palladium Complex of Tropyne

1996

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“…According to an electron diffraction (ED) and a microwave (MW) investigation of CHT [4,51, the molecule is nonplanar and possesses a boat form. This has been confirmed by X-ray studies of the substituted CHTs [6][7][8][9] and AZPs [lo-121 shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 62%

Theoretical determination of molecular structure and conformation

Cremer

Dick

Christeu

1984

Journal of Molecular Structure: THEOCHEM

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Restricted Hartree-Fock calculations have been carried out for 1,3,&cycloheptatriene, norcaradiene, lH-azepine, benzenimine (azanorcardiene), oxepine and benzene oxide (oxanorcaradiene) employing the STO-3G, 4-31G and 6-31G* basis sets. Theoretical geometries, conformations and barriers to ring inversion have been obtained and compared with the available experimental structural data. It has been found that the cyclotrienes possess a boat conformation with a constant admixture of 22% chair character leading to a flattening of the triene part and n-electron delocalization typical for a planar polyene. The structural data obtained in this work suggest that cyclic delocalization of either 6~ (homoaromaticity) or 8~ electrons (antiaromaticity) is not present in the three cyclotrienes. The former possibility, however, cannot be excluded in the case of the three norcaradienes. 5 .6 :, X7 p" (c D 2 X=CHz X 4 X=NH 6 X=0 2 ' CHT may obtain some aromatic character by 1,6 overlap of 2pn-orbitals and a homoconjugative closure of the triene part. In NCD, however, interactions between the n-molecular orbit& (n-MOs) of the diene part and the

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“…A number of conjugated organic molecules have so far been prepared, some of which are known experimentally to assume nonplanar structures in the ground and electronically excited states. − From the viewpoints of structural characteristics, chemical reactions, and physicochemical properties, a degree of pyramidalization in nonplanar conjugated molecules has attracted a good deal of attention, and the topics on measures of pyramidalization have been reviewed by several authors. − As will be shown below, since the total energy of a molecule can be partitioned into the four energetic components, our interest in nonplanar conjugated molecules is to elucidate what happens inside the molecule when it is subject to the pseudo-JT distortion from planarity. In such a structural change, it will be expected that non-nearest-neighbor interactions become important, according as the molecule folds its molecular skeleton.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio MCSCF Study on the Pseudo-Jahn−Teller Distortion from Planarity in Cycloheptatriene, Heptalene, and Heptafulvalene

2000

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To elucidate the nature of a pseudo-Jahn-Teller (JT) distortion from planarity, ab initio MCSCF calculations with 6-31G(d) basis sets are carried out on the ground state of the titled molecules. Cycloheptatriene undergoes the pseudo-JT distortion from a planar C 2V to a boat C s conformation. In heptalene, the pseudo-JT distortion takes place in two stages, the initial step being from a symmetric planar D 2h to a skew planar C 2h structure and the subsequent step from the skew C 2h to a twisted C 2 one. In heptafulvalene, the symmetric planar D 2h structure exhibits a third-order saddle point and, hence, the pseudo-JT distortions take place from the D 2h to D 2 , C 2V , and C 2h ones through the respective out-of-plane nuclear deformations. Besides, the twisted D 2 structure exhibits a second-order saddle point with respect to the syn-and anti-folding motions of the sevenmembered rings and the structural changes take place from the D 2 to the C 2V and C 2h structures. A comparison of the total energy reveals that the ground state of heptafulvalene takes the anti-folded C 2h conformation. These structural characteristics are in good agreement with the available experimental facts. Energy component analyses reveal that in these molecules the pseudo-JT distortion from planarity should lead markedly to a lowering of the electron-nuclear attraction energy and concomitantly to raising of both the interelectronic and the internuclear repulsion energy. These energetic behaviors are accounted for in terms of the electrostatic interactions and the proximity between the nuclei and electron clouds involved in the CC and CH bonds, owing to the folding of the carbon skeleton.

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Structure and conformation of substituted cycloheptatrienes. I. 2,5-Dimethyl-3,4-diphenyl-1,3,5-cycloheptatriene

Cited by 10 publications

References 7 publications

Bis(triphenylphosphine)palladium Cycloheptadienynylium Tetrafluoroborate: A Palladium Complex of Tropyne

Bis(triphenylphosphine)palladium Cycloheptadienynylium Tetrafluoroborate: A Palladium Complex of Tropyne

Theoretical determination of molecular structure and conformation

Ab Initio MCSCF Study on the Pseudo-Jahn−Teller Distortion from Planarity in Cycloheptatriene, Heptalene, and Heptafulvalene

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