Inorganic anion receptors macrocyclic

Polyammonium macrocycles and macropolycycles have been studied most extensively as anion receptor molecules. They bind a variety of anionic species (inorganic anions, carboxylates, phosphates, etc.) with stabilities and selectivities resulting from both electrostatic and structural effects. 

Cholic acid has been converted into a series of electroneutral anionophores targeted at inorganic anions. These may be divided into two categories acyclic and macrocyclic receptors that exploit the H-bonding properties of (at least some of) the secondary hydroxyls, and acyclic podands in which all the hydroxyl groups were modifed to give alternative binding functionality. These two classes are considered separately below. 

In the last few years there has been considerable interest in development of new aza and oxa-aza macrocyclic receptors. Macrocyclic molecules containing appropriate binding sites and cavities of suitable size and shape may be designed to form selective inclusion complexes. Actually, the molecular topology of the host molecule can be synthetically modulated in order to bind many different chemical species. To this purpose, aza or oxa-aza macrocyclic receptors able to bind different kinds of substrates, such as inorganic or organic cations,anionic species, " and neutral molecules have been studied to elaborate their use as selective recognizers, molecular carriers and catalysts. 

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