Anion receptors containing ammonium binding sites

1 Anion receptors containing ammonium binding sites 

Linear anion recognition. The hexaprotonated form of the ellipsoidal cryp- 

Macrocyclic systems—polyazamacrocycles. Anion complexation can only occur when over a certain range of pH the anion exists and the host ligand is in its protonated form. With the macropolycyclic systems previously described, this prerequisite for binding is obeyed for halide and azide guest anions. However, for the important classes of carboxylate and adenosine 

Macrocycle (117), based on ethylene diamine units, forms the most stable complexes with the highly charged anions oxalate, sulphate and to a lesser extent AMP, ADP and ATP. The receptor (116) has the largest cavity and exhibits the greater log values for the large anions citrate, trimesate, Co(CN)r and Fe(CN).  

The binding of anions like Co(CN) , Fe(CN)6 and Ru(CN)6 by (115)-6H and (116)-8H is an example of second sphere coordination (111) with the transition metal cation complexed by cyanide anions which are, in turn, bound to the receptors by multiple I -H-NC-M hydrogen bonds 

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Anslyn and coworkers [56,57] synthesized receptors containing Cu(II) binding sites with appended ammonium 69 and guanidinium 70 groups. These receptors showed high affinities for tetrahedral anions such as HPO " and... 

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