Calix[4]pyrrole based receptors for the recognition of ion pairs

Identifier:  TDX:3406

Handle: https://hdl.handle.net/20.500.11797/TDX3406

Authors:  Molina Muriel, Ricardo

Abstract:
This thesis describes the synthesis and binding studies of supramolecular synthetic receptors. The receptors are based on calix[4]pyrrole architectures, able to interact with charged and neutral polar molecules by the establishment of hydrogen bonding interactions. The binding studies were performed in chloroform by means of NMR and ITC experiments and in the gas phase by ESI-MS techniques. We present the synthesis of a two-wall bis(calix[4]pyrrole) receptor based on two calix[4]pyrrole units linked by a triazole spacer. The synthetic receptor was able to bind tetraalkylammonium ion pairs of cyanate and chloride with high binding affinity, displaying different binding geometries and cooperativity depending on the bound cation. We then investigated the formation of [2]-pseudorotaxane complexes assisted by the same ion pairs, using a lineal N-oxide as the axle. We observed the formation of two different isomeric forms of the complexes obtained attending to the binding of the anion and the axle on each of the two different hemispheres of the receptor. We also report the synthesis of the [2]rotaxane receptor obtained by stoppering strategy and briefly discussed the binding properties towards ion-pairs. Finally, we describe the synthesis and binding studies of a strapped calix[4]pyrrole macrocycle decorated with a bis-amide unit as the strap.