PE‐spectroscopic investigation of nonconjugated π,π interactions in (seco)dodecahedradienes — on the route to an experimental ethylene/ethylene cycloaddition reaction coordinate

Nature and extent of nonconjugated π,π interactions in (bis)‐secododecahedradienes and (pentagonal, non‐pentagonal) dodecahedradienes with transannular π,π distances ranging from ca. 2.8 to ca. 3.5 Å – representing well defined points on the D2h [π2 + π2] reaction coordinate – were studied by PE spectroscopy. The π,π splitting of 0.68 eV measured at the largest π,π distance of ca. 3.5 Å (1,16‐dodecahedradiene 3a) was attributed to ca. 50% each of through‐space and through‐bond conjugation (analysis of precanonical MOs).