SMALL AND MEDIUM RINGS .78. CAGE DIMERS OF NORBORNADIENE WITH PERPENDICULAR ARRANGEMENT OF SUBCHROMOPHORES - ORBITAL INTERACTION IN THE HEPTACYCLO (6.6.0.0(2,6).0(3,13).0(4,11).0(5,9).0(10,14))TETRADECANE SYSTEM

The syntheses of functionalized norbornadiene dimers 1 are described. These cage compounds feature remarkably high D2d symmetry as regards the dimethylene and dioxo derivatives 1d and 1e. On the other hand, the mixed enone compound 1f behaves differently: pi(CC) and lone-pair n(CO) orbitals mix strongly with each other, albeit only be means of the intervening five-bond sigma-system. All theoretical conclusions have been verified by using PE spectroscopy. A comparison is made between systems 1 and the geometrically similar adamantanes 2, on the one hand, and the attractive but still unknown derivatives of garudane 3 on the other hand. The latter exhibit the interesting parallel topology of suitable chromophores, thus making these polycycles 3 desirable candidates for transmission studies.