Small and Medium Rings, 771) Nonconjugated π,π Interactions Approaching Classical π,π Conjugation – PE‐Spectroscopical Investigation of the 7,8;12,19‐Diseco‐1,16‐dodecahedradiene System

Transannular (orbital) interactions in compounds 1–9 are studied by means of He(Iα)‐PE spectroscopy. Unusually strong through‐space‐dominated π,π interaction is found to be operative in the nonconjugated 1,6‐dienes 1, 2, 7, and 8. The π,π splitting of 1.9 eV for disecododecahedradiene 1 is even surpassed by the record value of 2.2 eV for disecodienedione 2, which almost equals that in 1,3‐butadiene (2.46 eV). The experimental results are explained by computational methods, especially by analyses of the precanonical MOs.