[4.4]-Spirononatetraene belongs to symmetry D2d in its normal state. The extent of its Jahn-Teller instability with respect to a torsion taking it to D2 symmetry in an excited degenerate electronic state is calculated by an ab initio method, with STO/3G in SCF/CI. The equilibrium structure is found to be displaced 2.5°from D2d and is more stable by ≈ 110 cm-1, though neither result is very precise. The calculated rotatory strength of the lowest frequency optically active electronic transition is found to be negative for the R (or M) enantiomer. The lowest energy singlet transition of the D2d molecule is found to be 1B1 ← 1A1, lower by ∼ 10 000 cm-1 than the Jahn-Teller active 1E ← 1A1, earlier suggested to be the lowest transition.
|Number of pages||8|
|Journal||Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics|
|Publication status||Published - 1979|