Host-Guest Chemistry of Aromatic-Amide-Linked Bis- and Tris-Calix[4]pyrroles with Bis-Carboxylates and Citrate Anion

A small library of polytopic receptors has been synthesized from meso-p-and meso-m-aminophenylcalix[4]pyrroles and p-or m-phthaloyl or trimesic chloride. Selected bis-carboxylates and the citrate anion, which either exhibit altered distribution profiles in cancerous tissues in comparison with healthy tissues or are metabolites of carcinogenic substances (for example, trans, trans-muconic acid from benzene exposure in humans) were tested as ligands. Varied affinities and binding modes were observed as a function of the number of calix[4]pyrroles and the topology of amide units present in each of the polytopic receptors. The structures of the 1:1 complexes derived by molecular modeling are in excellent agreement with the results of H-1 NMR complexation studies.