Stabilities of Hydrogen-Bonded Supramolecular Complexes with Various Numbers of Single Bonds: Attempts To Quantify a Dogma in Host-Guest Chemistry

The disadvantage of flexible bonds in supramolecular host–guest complexes is much smaller than usually assumed. In the association of dicarboxlic acids with diamides (shown on the right), freely rotatable single bonds have only a minor disadvantageous influence on the free energy of complexation ΔGcplx. From the linear correlation between ΔGcplx and the number of single bonds n, a decrease in the free energy of complexation of only 1.3 kJ mol−1 per single bond was determined.