Three different macrocycles with an increasing degree of flexibility, but all with 26 atoms in the macrocyclic ring were designed as anion receptors to find the optimal compromise between preorganization and flexibility (Figure ). Macrocycle 1 was designed to be the most rigid of the three. It employs dipicolinic bisamides, which are known to prefer a syn-syn configuration due to interactions of the amide NH and the lone pair on the pyridyl N, as well as phenanthrene spacers to give rigidity and the desired appropriate macrocyclic ring size. This in turn was envisaged to result in preorganization of the amides to accommodate H2P2O7 2-in the binding cavity. Macrocycle 2 was designed to be more flexible, replacing the dipicolinic bisamide motif with isophthalic acylhydrazones. This could potentially also lead to interactions from the CH proton of the isophthalic subunit between the two acylhydrazones, which has been reported to be able to participate in anion binding. Macrocycle 3, employing bis-N-(benzyloxy)isophthalamides, was designed to be the most flexible. The n-hexyl and ethyl ether groups of 1 and 3 respectively, as well as tert-butyl groups of 2 and 3 are present to enhance the solubility of the macrocycles in organic solvents as required for anion binding studies.