Half-substituted fluorocycloparaphenylenes with high symmetry: Synthesis, properties and derivatization to densely substituted carbon nanorings

Cycloparaphenylenes (CPPs) are ring-shaped aromatic hydrocarbons in which benzene rings are connected to each other at the para-positions. In recent years, fluorinated CPPs (FCPPs) have attracted much attention as electron-accepting CPPs as well as strained fluoroarenes. Herein, we report the synthesis, properties, and derivatization of novel FCPPs; F16[8]CPP (1) and F12[6]CPP (2), in which ortho-difluorophenylene units are circularly connected to form CPP structure. The short-step synthesis of 1 and 2 has been achieved by the strategy using macrocyclic nickel or gold complexes. Furthermore, the derivatization of 1 was successfully achieved to afford a new heteroring-containing carbon nanoring; hexadecapyrrolyl[8]cycloparaphenylene 5, where 16 pyrrole rings are densely substituted on CPP framework.