2,3-Dimethylenecyclohexa-1,3-diene diradical is a ground-state triplet

Dowd, Paul; Chang, Wonghil; Paik, Yi Hyon

doi:10.1021/ja00251a046

Cited by 53 publications

(29 citation statements)

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“…The same authors22 also find that the D values are predicted to be approximately 0.226 cm-1, an order of magnitude higher than that observed. Since the three TME triplets 1- 3 have D values of 0.025,0.025, and 0.0259 cm-1, respectively, the calculated value22 seems clearly to be out of the acceptable range.…”

Section: Synthesismentioning

confidence: 84%

Tetramethyleneethane-d8

Dowd¹,

Chang²,

Partian³

et al. 1993

J. Phys. Chem.

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Tetramethyleneethane (TME) is a triplet non-KekulC molecule that is currently the source of a difference between theory and experiment. The best theory places the energy of the triplet about 1 kcal/mol below the singlet at an angle of twist of 50° about the central carbon4arbon bond. However, the triplet ESR spectrum shows no splitting between the x-and y-lines, indicating that the zero field parameter, E, is 0 or very small. If it is the former, that would be consistent with a D u configured TME. In order to explore this point by removing proton hyperfine coupling, TME-ds was prepared. Again, no splitting was observed between the xand y-lines for TME-dg. This sets an upper limit for E of approximately 0.001 cm-l.

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Section: Synthesismentioning

confidence: 84%

Tetramethyleneethane-d8

Dowd¹,

Chang²,

Partian³

et al. 1993

J. Phys. Chem.

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“…For example, the sum of ρ at C6 and Σρ of 1 3 •• [+0.75 = +0.59 + (+0. 16)] and that of 3 On the basis of the comparison of 3 •• and 7 •• , the phenyl groups appear to provide only a small perturbation to the spin distribution of the latter species. This is attributed to the calculation result that θ of 7 •• (40˚for 1 7 •• and 3 7 •• ) is larger than that of 3 •• (27˚for 1 3 •• and 25˚for 1 3 •• ), as shown in Table 2.…”

Section: Spin Densitiesmentioning

confidence: 99%

“…1) [1][2][3][4][5][6][7][8][9][10][11][12] is a prototypical non-Kekulé molecule, composed of two allyl radical moieties that have no significant interaction with each other. Experimental [13][14][15][16][17][18][19][20][21][22][23] and theoretical [24][25][26][27][28][29][30] interest in this reactive intermediate is stimulated by its unique electronic structure including multiplicity. The energy gap between the singlet and triplet states (S-T gap) of 1 •• is small and, as a result, substitution by functional groups or changes in dihedral angles (ω, Fig.…”

Section: Introductionmentioning

confidence: 99%

Density functional theory study of silole‐fused tetramethyleneethane biradicals with orbital interactions

Kano

Mizuno

Ikeda

2011

J of Physical Organic Chem

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The geometries, energy gap between singlet and triplet states (S–T gap), electronic transitions, and molecular orbitals of the diphenyl derivative of the silole‐fused tetramethyleneethane (TME) (3,4‐dimethylenesilole) biradical 7•• were determined by using the density functional theory method at the unrestricted Becke, three‐parameter, Lee–Yang–Parr/cc‐pVDZ level. In a manner similar to that of the parent TME biradical, the S–T gap of 7•• is small. The wavelengths of electronic transitions of 37•• (λET = 450 nm) are calculated to be different from that of 17•• (λET = 673 nm). These differences are attributed to interactions between orbitals of the two allyl radical moieties, especially, the existence of double σ*–π* conjugation, that is, π*–σ*–π* conjugation, that takes place in the silole subunit. Copyright © 2011 John Wiley & Sons, Ltd.

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“…In 1986, 20 Dowd et al exploited an alternative synthesis, produced 3 and established experimentally that it is a ground-state triplet. Because it was unclear whether the triplet ground-state of 3 is planar, Dowd et al 21 prepared the conformationally restrained system 5 and showed that it too is a ground-state triplet. They then concluded that planar 5 is a ground-state triplet.…”

Section: For An Example)mentioning

confidence: 99%

“…They then concluded that planar 5 is a ground-state triplet. 21 Subsequently, Borden and Du reported 22 that ab initio calculations predict that both planar and nonplanar 3 have a singlet ground state. The singlet was predicted to prefer the perpendicular geometry.…”

Section: For An Example)mentioning

confidence: 99%

Disjoint nonclassical hydrocarbons have very unstable lowest-lying singlet states: a PM3 study

Langler¹

2001

Quím. Nova

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Earlier workers have suggested that disjoint hydrocarbons have nearly-degenerate lowest-lying singlet and triplet states while non-disjoint (or joint) hydrocarbons should be ground-state triplets. PM3 results for an appropriate selection of alternant hydrocarbons are inconsistent with that generalization: disjoint, nonclassical, alternant hydrocarbons show the strongest predilection for triplet ground states

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2,3-Dimethylenecyclohexa-1,3-diene diradical is a ground-state triplet

Cited by 53 publications

References 0 publications

Tetramethyleneethane-d8

Tetramethyleneethane-d8

Density functional theory study of silole‐fused tetramethyleneethane biradicals with orbital interactions

Disjoint nonclassical hydrocarbons have very unstable lowest-lying singlet states: a PM3 study

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