Fig. 1. (A) Representative structural parameters of dihetero[8]helicenes. (B) Time-course of ee of dihetero[8]helicenes at 533.15 K. (C) Calculated isomerization process of 6O. (D) Summary of structural features and racemization dynamics. ^aSee Fig. S21‡ for the detailed definition for the wedge angle. ^bDFT calculation was conducted at the B3LYP-D3(BJ)/6-311G(d,p) level of theory in the gas phase. ^cThe structural parameters were obtained by X-ray single crystal diffraction analysis of the racemates. Estimated values based on DFT calculations are shown in parentheses. The structure of carbo[8]helicene shown in the first row was obtained by DFT calculation. ^dExperimental half-life time of ee at 533.15 K in tetraglyme. ^eExperimental value at 531.76 K taken from ref. 22. ^fActivation free energies for racemization at 533.15 K. ^gEstimated by experimentally obtained values of ΔH^‡ and ΔS^‡ taken from ref. 22.