Synthesis of Twisted [n]Cycloparaphenylene by Alkene Insertion

Abstract

AbstractMono‐alkene‐inserted [n]cycloparaphenylenes 1 [(ene)‐[n]CPP] with n=6, 8, and 10, mono‐ortho‐phenylene‐inserted [6]CPP 2, and di‐alkene‐insertved [n]CPP 3 [(ene)2‐[n]CPP] with n=4, 6, and 8 were synthesized by fusing CPP precursors and alkene or ortho‐ phenylene groups through coupling reactions. Single‐crystal X‐ray diffraction analyses reveal that the strips formed by the π‐surfaces of 1 and 2 exhibited a Möbius topology in the solid state. While the Möbius topology in the parent 1 and 2 in solution was lost due to the free rotation of the paraphenylene unit even at low temperatures, ene‐[6]CPP 4 with eight 1‐pyrrolyl groups preserved the Möbius topology even in solution. Despite a twist, 1 has in‐plane conjugation and possesses a unique size dependence of the electronic properties: namely, the opposite size dependency of the HOMO–LUMO energy relative to conventional π‐conjugated molecules.