Fig. 2. Calculation of the height of the rotation barrier for compounds 1–4. (A) Conformational energy profile obtained for the gas phase at the B3LYP/6-31G(d) level of theory for the rotation about the central biaryl bond in the model compound 8,8′-dihydroxy-3,3′-dimethoxy-2,2′-binaphthyl-1,1′,4,4′-tetrone. Vertical lines separate regions of values for the torsion angle that correspond to distinct conformations according to the Klyne–Prelog notation. The structures of the Ra and Sa atropisomers are assigned to the corresponding minimum-energy conformers in the anticlinal conformations. (B) Visualization of the distinct conformers according to the Klyne–Prelog notation. The height of the black line indicates the relative energy of the depicted conformer.
