Charged receptors

A tetraamidinium functionalized, bowl-type cavitand (receptor 8) was developed by Diederich and Sebo [47]. This receptor was found to complex 1,3-dicarboxylate anions with good selectivity and a 1 2 binding stoichiometry both in CD3OD and D20, as revealed by standard Job plot analysis. In contrast, various nucleotide phosphates were found to be bound with a 1 1 stoichiometry in D20. In the case of the adenosine phosphates, the association constants increased as a function of nucleotide charge [i.e., the affinity order (K., M-1) was cAMP (1400) < AMP (10000)[Pg.322]

C. Charged Receptors Based Primarily on Electrostatic Attraction... 

Positively charged receptors based on multiple coordination interactions from transition metals. 

Charged receptors based primarily on intermolecular electrostatic attraction from positively charged metal centers. 

The results show that a field is suitable for the description of the interaction of ligands with a positively charged receptor group, while a H2O probe in GRID describes hydrophobic as well as hydrogen-bonding effects [1019, 1023],... 

Much stronger complexation can be achieved if charged substrates are targeted with oppositely charged receptors as already noted above while referring to receptor 7 (Scheme 7). Other examples for the successful realization of this concept are cationic receptors 15-17 (Scheme 11) that strongly bind to 5-A-acetylneuraminic acid NeuSAc in... 

An example of a positively charged receptor that binds to phosphate esters of monosaccharides is 18 (Scheme 12). This compound contains three guanidiniocarbonyl pyrrole-derived substituents around the aromatic core, a building block introduced by the Schmuck group as a binding site for... 

Fig. 12.14 Limiting extraction approaches that maintain charge neutrality. These involve, respectively, the use of (a) A positively charged receptor, (b) a ditopic receptor, (c) two different receptors, and (d) an anion receptor assisted by a lipophilic cation [47], This diagram is a redrawing of a scheme first reptnted by Gale and cowoikers and which appeared in [47]...

Ashton, P.R., Odell, B., Reddington, M.V., Slawin, A.M.Z., Stoddart, J.F. and Williams, D.J. (1988) Isostructural Alternately-charged Receptor Stacks. The Inclusion Complexes of Hydroquinol and Catechol Methyl Ethers with Bisparaquat(l,4)cyclophane Angew. Chem. Int. Ed. Engl. 27,1550. 

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