Orbital interactions. Part 13. The observation of through-bond orbital interactions between benzene and double bonds in some dimethanoanthracenes

Abstract

The He1 photoelectron spectra of the structurally rigid dimethanoanthracenes (5)–(8) have been measured and their spectra have been assigned on the basis of band intensities, ionization energy correlations with related molecules, and ab initio SCF molecular orbital calculations. The results reveal the presence of large through-bond orbital interactions in (7) and (8) which destabilize the symmetric aromatic π-based orbital to a greater extent in the all-trans configuration (7) and the ethylenic π-based orbital more in the trans–cis configuration (8). This last result reveals yet another example which demonstrates the existence of a novel laticyclic through-bond orbital interaction which is relayed through methylene groups. The antisymmetric aromatic π-based orbitals in (7) and (8) appear not to be affected by any orbital interactions.