Preparation of a large-sized highly flexible carbon nanohoop.

The preparation of large-sized carbon nanohoops 1 and 2 was acheieved by Pt-mediated macrocyclization of the diborylated hexa-peri-hexabenzocoronene (HBC) derivative containing four mesityl substituents at the periphery. The temperature-dependent NMR measurements revealed the highly flexible nature of the carbon nanohoop 1. Structural features of 1 and 2 were examined by comparison of photophysical and electrochemical measurements with those of the reference non-strained HBC derivative. Theoretical calculations clarified the possible molecular structure of the carbon nanohoops 1 and 2 and the structures involved in the dynamics.