By repositioning the five-membered rings of dicyclopenta[b, g]naphthalene on the napthalene core, we obtain dicyclopenta[a, h]naphthalene. Despite exhibiting out-ofplane bending due to steric congestion at the R 1 position, which leads to distortion of ∼ 7 • in the bare molecule (R 1 =H) and ∼ 24 • when R 1 =OMe, S 1 -T 2 inversions are observed in the substituted molecules. Substituted dicyclopenta[b, g]naphthalenes have been reported as reaction intermediates. Cyclopenta[de f ]fluorene is similar to our previously-reported isopyrene (Figure ) in that a pentalene core is flanked by symmetric fused ring systems. However, unlike isopyrene, whose planarity and bond-delocalization are enabled by push-pull aromaticity, cyclopenta[de f ]fluorene is bowl-shaped, exhibits bondlength alternation and is signficantly antiaromatic in the ground state (Figure ). Through di-and tetra-substitution at the sixmembered rings with electron-donating groups, the antiaromaticity of the ring systems is alleviated and inversions between the S 1 and T 2 are obtained due to the double-bond delocalized structures. To the best of our knowledge, cyclopenta[de f ]fluorene has not been synthethically reported.