Computational studies using a semi-empirical PM7 approach in MOPAC were carried out for each of the three receptors without guest, with H2P2O7 2-, and with the much smaller Cl -anion to gain insights in the differences in the conformation of the receptors. In the absence of any guest (Figure ), macrocycle 1 adopts a preferred conformation with all the NHs pointing into the cavity, suggesting a good preorganization for H2P2O7 2-binding. Macrocycle 2 adopts a preferred conformation with two of the NH groups pointing into and the other two pointing out the cavity. Macrocycle 3 exhibits intramolecular H-bonding, with two of the NH protons interacting with carbonyl groups pointing towards the interior of the cavity and the other two NH protons pointing outwards.