Dibenzo[ a,o ]picene: A Semiconducting Nonplanar Heptacene Isomer

We report a concise two-step synthesis of the elusive heptacene isomer dibenzo[a,o]picene via regioselective Mallory photocyclization of a bis(stilbenyl)phenanthrene precursor. DFT calculations rationalize the observed regioselectivity and confirm the aromatic, highly stable framework. Dibenzo[a,o]picene exhibits a 2.98 eV optical band gap, reversible oxidation, and a low-lying HOMO. Single-crystal X-ray analysis reveals one-dimensional π-stacking (3.31 Å). Single-crystal OFETs display p-type hole mobilities of 3.2 × 10^-3 cm² V^-1 s^-1, establishing this long-sought isomer as a promising air-stable semiconductor.