The tetramethyleneethane (2,2'-diallyl) anion radical

Bauld, Nathan L.; Stevenson, Gerald R.

doi:10.1021/ja01041a058

Cited by 15 publications

(3 citation statements)

References 4 publications

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“…In particular, the magnetic equivalence of the two different kinds of protons of TME found in the EPR spectrum is borne out by the equal negative spin densities computed at the corresponding hydrogen centres. Further, similar data for the TME radical cation and anion are also consistent with the experimentally observed proton hyperfine coupling constants (Bauld and Stevenson 1969;Gerson et al 1989). The pleasing agreement between the computational and experimental spectral results confirms that the EPR study of TME has indeed been carried out on the lowest energy triplet.…”

Section: Resultssupporting

confidence: 82%

Is tetramethyleneethane a ground state triplet?

Chakrabarti

Albert

Ramasesha

et al. 1993

Proc. Indian Acad. Sci. (Chem. Sci.)

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We have examined a number of possible ways by which tetramethyleneethane (TME) can be a ground state triplet, as claimed by experimental studies, in violation of Ovcbinnikov's theorem for alternant hydrocarbons of equal bond lengths. Model exact n calculations of the low-lying states of TME, 3,4-dimethylenefuran and 3,4-dimethylenepyrrole were carried out using a diagrammatic valence bond approach. The calculations failed to yield a triplet ground state even after (a) tuning of electron correlation, (b) breaking alternancy symmetry, and (c) allowing for geometric distortions. In contrast to earlier studies of fine structure constants in other conjugated systems, the computed D and E values of all the low-lying triplet states of TME for various geometries are at least an order of magnitude different from the experimentally reported values. Incorporation of ~r-n mixing by means of UHF MNDO calculations is found to favour a singlet ground state even further. A reinterpretation of the experimental results of TME is therefore suggested to resolve the conflict.

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Section: Resultssupporting

confidence: 82%

Is tetramethyleneethane a ground state triplet?

Chakrabarti

Albert

Ramasesha

et al. 1993

Proc. Indian Acad. Sci. (Chem. Sci.)

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“…Finally, we note that Y-delocalized systems may be coupled or fused together to make larger stabilized systems, just as benzene may; some stable derivatives of this type are illustrated in Figure 6 (25-28). Ten pi-electron systems of the tet.ra(dialkylamino)ethylene (VIII) type may be considered to be derived from the pi-system of the known tetramethylene-ethane dianion (29). The 8 pi-electron, diradical hydrocarbon (IX) in this series has also been studied (80).…”

Section: Heteronuclear Analogs Of Trimethylenemethanementioning

confidence: 99%

Guanidine, trimethylenemethane, and "Y-delocalization." Can acyclic compounds have "aromatic" stability?

Gund¹

1972

J. Chem. Educ.

211

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“…This is confirmed for example by the finding that, on ionization, hexa-1,5-diene or semibullvalene collapse spontaneously to symmetric radical cations with a structure like that of the diradicaloid transition states for their degenerate Cope rearrangement (Scheme 2), which led Williams to coin the term 'inverted potential energy surface' for such cases. 20 Other examples of stable diradical ions that were studied in condensed phase include the radical cations of cyclopentane-1,3-diyl 21, 22 and trimethylenemethane 23 as well as the radical anion 24 and cation of tetramethylene ethane 25 whose neutral had also been studied by Dowd. 26 More recently, ionized diradicals have been studied extensively in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

Generation and identification of 1,4-perinaphthadiyl radical cation—first observation of the electronic absorption spectrum of an ionized diradical

Zhu¹,

Bally²,

Wirz³

et al. 1998

J. Chem. Soc., Perkin Trans. 2

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Irradiation of 6b,7,8,8a-tetrahydrocyclobut[a]acenaphthylene (CAN) in haloalkane glasses at 77 K yields a persistent radical cation, CAN ϩ , whose electronic absorption spectrum has been obtained. Irradiation at >640 nm converts this into an isomer which is identical with that formed by ionization of 1,4-dihydro-1,4-ethanonaphtho[1,8-de][1,2]diazepine (END) and subsequent irradiation of the radical cation at > 540 nm. In both cases, further irradiation at 450 nm yields the radical cation of 1,8divinylnaphthalene (DVN ϩ ) which was identified by ionization of DVN generated in situ by photolysis of CAN. These related observations identify the photoisomer of CAN ϩ as 1,4-perinaphthadiyl radical cation (7,8,9,10-tetrahydrocyclohepta[de]naphthalene-7,10-diylium, CND ϩ ).The molecular and electronic structures of all observed radical cations, as well as their electronic absorption spectra, are discussed on the basis of B3LYP and CASPT2 quantum chemical calculations and, in the case of CAN ϩ and DVN ϩ , also by reference to the photoelectron spectra of the neutral hydrocarbons. The CAN ϩ →PND ϩ →DVN ϩ sequence of photoreactions is discussed on the basis of orbital and state correlation diagrams.

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The tetramethyleneethane (2,2'-diallyl) anion radical

Cited by 15 publications

References 4 publications

Is tetramethyleneethane a ground state triplet?

Is tetramethyleneethane a ground state triplet?

Guanidine, trimethylenemethane, and "Y-delocalization." Can acyclic compounds have "aromatic" stability?

Generation and identification of 1,4-perinaphthadiyl radical cation—first observation of the electronic absorption spectrum of an ionized diradical

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