The strain energy of nanohoops (S)-PO4H- [9]CPP and (S)-OH- [9]CPP was determined using the homodesmotic reaction model, providing nearly identical values of 40 and 42 kcal mol -1 , respectively. The difference in strain energy between the phosphoric acid derived nanohoop ((S)-PO4H-[9]CPP) and the BINOL derived molecule ((S)-OH-[9]CPP), while relatively small, is likely real, because it is and reflected in the deviation of the BINOL torsion angle in the ring versus the relaxed geometry, which is larger for the non-tethered (S)-OH- [9]CPP macrocycle (Supplementary Fig. ).