Curved π-conjugated corannulene dimer diradicaloids.

So far, most reported open-shell singlet diradicaloids are based on planar π-conjugated molecules. Herein, we report the bridged corannulene dimer diradicaloids, and , both showing a three-dimensional curved π-conjugated structure. has a small diradical character ( = 5.4%) and behaves more like a closed-shell quinoidal compound at room temperature, while is a typical open-shell diradicaloid with a larger diradical character ( = 16.9%). Both compounds exhibited paramagnetic activity at elevated temperatures, with a singlet-triplet energy gap (Δ) of -8.4 and -3.0 kcal mol, respectively. X-ray crystallographic analysis revealed that both molecules have a dumbbell-shaped geometry, with the two terminal corannulene bowls bent to opposite directions. The spin is largely delocalized onto the two bowls in and there are multiple [CH···π] interactions between the neighboring bowls. Chemical oxidation/reduction to their respective dications/dianions results in global aromaticity with [4 + 2] π-electrons delocalized through the periphery of the whole framework.