Aromatic Saddles Containing Two Heptagons

Soluble derivatives of C₇₀H₂₆ (<b>1a</b>,<b>b</b>) and C₇₀H₃₀ (<b>2a</b>,<b>b</b>), two new saddle-shaped polycyclic arenes containing two heptagons, were successfully synthesized from saddle-shaped diketones (<b>3a</b>,<b>b</b>), whose carbonyl groups are the key in the reactions to extend the polycyclic π-framework. As found from the crystal structures, the polycyclic backbone of <b>1b</b> has a deep saddle shape, while that of <b>2b</b> is even more distorted because of the existence of two [4]-helicene moieties. On the basis of crystal structures, local aromaticity and nonplanarity of individual rings in the saddle-shaped π-backbone were analyzed, and were found to follow Clar’s rule in general. It was found that <b>1b</b> and <b>3b</b> behaved as p-type semiconductors in solution-processed thin film transistors while the amorphous films of <b>2b</b> appeared insulating