Synthesis, structure, and complexing properties of macrocyclic receptors for anions

Abstract

Understanding of structure-affinity relationships is crucial for rational receptor design, however, such studies for anion receptors are still limited. Therefore, we investigated this issue in the case of amide-based macrocyclic receptors derived from aromatic diacids (i.e., isophthalic and dipicolinic). Using these model compounds, we examined the macrocyclic effect, the influence of intramolecular hydrogen bonds, and the correlation between the ring size and anion affinity. We found that in contrast to what was known for acyclic diamides, macrocyclic isophthalamide receptors bind anions more weakly than their dipicolinic analogs. Comprehensive structural studies revealed that such behavior is due to intramolecular hydrogen bonds present in isophthalamide receptors. Furthermore, we demonstrated how this obstacle can be overcome by the preparation of a hybrid macrocycle based on both building blocks.

Chelate effects in sulfate binding by amide/urea-based ligands

“…27 For the pyridine dicarboxamide ligands, the two amide groups are not constrained to be pointed in the same direction, but are frequently preorganized for chelation due to intramolecular hydrogen bonding interactions with the pyridine nitrogen atom. 28 Crystal structure results for the SO 4 complex with the simple diurea acycle 4 nicely illustrates the conformational flexibility of a host that is not preorganized for binding ( Fig. 4(a)).…”

Artificial Receptors for the Recognition of Phosphorylated Molecules

“…In the specific case of phosphate binding, amide and urea-based binding moieties have been the most commonly employed, reflecting their known ability to act as strong hydrogen-bond donors. 329,330 However, other subunits have been employed, as have systems containing several different hydrogen bonding functionalities. In this section, we present a discussion of neutral receptors that have been used for phosphate anion recognition.…”

Azulene‐Based Macrocyclic Receptors for Recognition and Sensing of Phosphate Anions

“…Symmetric receptor 2 , on the other hand, is derived from two azulene‐1,3‐dicarboxyamide units. To estimate the effect of the macrocyclic topology of 1 and 2 , linear analogues 3 and 4 were prepared and evaluated. Details of the synthesis of 1 – 4 , the structural studies and the anion binding studies are discussed herein.…”