2,3,4,5-Tetrahalogeno-1-(2,3-di-n-propylcyclopropenylidene)cyclopentadiene

Kitahara, Yoshio; Murata, Ichirô; Ueno, Masako; Shiota, Kunio; Watanabe, Haruyuki

doi:10.1039/c19660000180

Cited by 7 publications

(10 citation statements)

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“…The calculated dipole moments of 8 are large, with predicted values between 4.31 and 4.87 D. An experimental value of 5.63 D has been estimated from the experimental dipole moment of 2,3,4,5-tetrachloro-2‘,3‘-dipropyltriapentafulvalene (7.56 D) …”

Section: Discussionmentioning

confidence: 93%

Fulvalenes, Fulvenes, and Related Molecules: An ab Initio Study

et al. 1997

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Ab initio calculations using conventional (HF/6-31G and MP2/6-31G) and density functional theory (B-LYP/6-31G) methods have been used to determine the structures of the [n]fulvene and [n,m]fulvalene (n, m = 3, 5, 7) series of molecules, with particular emphasis on heptafulvalene (n = m = 7: 12). Calculations have also been performed on the parent cycloalkenes: cyclopropene, cyclopentadiene, and cycloheptatriene (1-3, respectively). All the fulvenes (n = 3, 5, 7: 4-6, respectively) and the smaller fulvalenes (n = 3, m= 3, 5, 7: 7-9, respectively, and n = m = 5: 10) are found to be planar. Pentaheptafulvalene (n = 5, m = 7: 11) adopts a very slightly nonplanar C(s)() arrangement of the five- and seven-membered rings. Heptafulvalene (12) is predicted to have an anti-folded C(2)(h)() structure, in accord with the X-ray crystal structure. We propose that the underlying reason for 11 and 12 adopting nonplanar conformations is the proximity of the H(2) and H(2)(') hydrogen atoms which promotes a distortion of the rings away from planarity at the central fulvalenic C=C double bond. In the process, pi-overlap is lost but this is partially regained by pyramidalization of the carbon centers in the seven-membered ring(s). The degree of folding is substantially more pronounced in 12 than in 11. Our calculated dipole moments, pi-electron distributions, bond alternation parameters, and energy comparisons indicate that the unknown smallest fulvalene, triafulvalene (7), is highly destabilized with localized bonding while triapentafulvalene (8), which is also unknown, is predicted to be stabilized and quite delocalized, consistent with Hückel 4n + 2 considerations.

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Section: Discussionmentioning

confidence: 93%

Fulvalenes, Fulvenes, and Related Molecules: An ab Initio Study

et al. 1997

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“…The significance of the zwitterionic mesomer is also evident in the high electrical dipole moments determined experimentally for some substituted calicenes. Thus, a value of 6.3 D was found for hexaphenylcalicene, 17 7.56 D for 1,2,3,4-tetrachloro-5,6-din-propylcalicene, 18 and 8.1 D for 1,2,3,4-tetrachloro-5,6-diphenylcalicene. 19 Calculated dipole moments for parent calicene 1 range from 4.3 to 5.6 D, 7,11,13,20,21 and a value of 5.63 D was estimated from an analysis of experimental data for analogous molecules.…”

Section: Introductionmentioning

confidence: 94%

Quantum Chemical Characterization of Low-Energy States of Calicene in the Gas Phase and in Solution

et al. 2007

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The ground and excited electronic state properties of calicene (triapentafulvalene or 5-(cycloprop-2-en-1-ylidene)cyclopenta-1,3-diene) have been studied with a variety of density functional models (mPWPW91, PBE, TPSS, TPSh, B3LYP) and post-Hartree-Fock models based on single (MP2 and CCSD(T)) and multideterminantal (CASPT2) reference wave functions. All methods agree well on the properties of ground-state calicene, which is described as a conjugated double bond system with substantial zwitterionic character deriving from a charge-separated mesomer in which the three-and five-membered rings are both aromatic. Although the two rings are joined by a formal double bond, contributions from the aromatic mesomer reduce its bond order substantially. A rotational barrier of 40-41 kcal mol -1 is predicted in the gas phase and solvation effects reduce the barrier to 37 and 33 kcal mol -1 in benzene and water, respectively, because of increased zwitterionic character in the twisted transition-state structure. Multistate CASPT2 (MS-CASPT2) is used to characterize the first few excited singlet and triplet states and indicates that the most important transition occurs at 4.93 eV (251 nm). A cis-trans photoisomerization about the inter-ring double bond is found to be inefficient.

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“…Our question in such a case is whether the energy of the lowest singlet state may be lowered by the interaction to such an extent that it lies below the symmetric (Czu) triplet ground state. As for molecule (7), the situation is quite similar to the case of molecule (2) and molecule (7) is also expected to lose its original full molecular-symmetry group ( D 2 3 and have a bond-alternating structure with the CZh ~y m r n e t r y . ~~ (iii) Molecules (4), (5), (S), and (9).…”

Section: Bjumentioning

confidence: 85%

“…1.2 eV) for symmetry reduction, irrespective of whether they are the 4n or 4n + 2 x-electron systems. Hence, these molecules are expected to undergo no symmetry reduction, retaining their original fully symmetrical nuclear arrangement^.^^ (ii) Molecules ( 2) and (7). The ground state of a molecule having an even number of electrons is usually a closed-shell singlet state.…”

Section: Bjumentioning

confidence: 99%

See 1 more Smart Citation

Double-bond fixation and aromatic stability in cyclic difulvalene systems

Toyota¹,

Nakajima²,

Koseki³

1984

J. Chem. Soc., Perkin Trans. 2

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On the basis of the second-order Jahn-Teller theory and of the semiempirical Pariser-Parr-Pople type SCF-M O method, w e have examined the energetically most favourable ground-state geometrical structures with respect to C-C bond lengths of cyclic difulvalene systems. The cyclic difulvalene systems examined are classified into t w o groups, one in which a molecule undergoes symmetry reduction from the fully symmetrical nuclear arrangement and the other in which a molecule suffers no symmetry reduction, suggesting that the former behaves as a polyolefin and the other as a typical aromatic hydrocarbon. This marked difference is explained in terms of a polarization stability by cyclization.

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2,3,4,5-Tetrahalogeno-1-(2,3-di-n-propylcyclopropenylidene)cyclopentadiene

Cited by 7 publications

References 0 publications

Fulvalenes, Fulvenes, and Related Molecules: An ab Initio Study

Fulvalenes, Fulvenes, and Related Molecules: An ab Initio Study

Quantum Chemical Characterization of Low-Energy States of Calicene in the Gas Phase and in Solution

Double-bond fixation and aromatic stability in cyclic difulvalene systems

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