Bond length alternations in some non-benzenoid aromatic hydrocarbons
Titel:
Bond length alternations in some non-benzenoid aromatic hydrocarbons
Auteur:
Nakajima, T. Katagiri, S.
Verschenen in:
Molecular physics
Paginering:
Jaargang 7 (1964) nr. 2 pagina's 149-159
Jaar:
1964
Inhoud:
The C-C bond length alternations in fulvene, heptafulvene, fulvalene, heptafulvalene, sesquifulvalene and heptalene are determined using, with slight modification, the theory of Longuet-Higgins and Salem [14]. It is shown that even in heptalene there exists a marked bond alternation, with the result that in this molecule the skew structure (C2h) is more stable than the symmetrical one (D2h). The charge densities, bond orders and free valences in the distorted structures are given. The obtained high free valences explain the chemical instability of these molecules. The transition energies and moments are calculated, electron interactions being taken into account. Numerical results are in good agreement with experimental spectral data. In this connection some previous assignments are confirmed and some new ones are proposed. The diamagnetic anisotropies, stabilization energies and vertical delocalization energies are also calculated. Bond alternations lead to considerable decreases in such quantities indicative of π-electron delocalization. All the above results agree that these molecules will have very little aromatic character.
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