Neutral Heterocyclic Receptors

Gale et al. recently reviewed designs of anion receptors [66-69], while amide-based macrocyclic receptors were detailed by Kang et al. [70,71). 

Chang et al. developed indole-based macrocycles 42 that had four indole N - H groups directed towards the inside of the large cavity (Fig. 15) [83]. The 

46b was used, the addition of the anion gave a yellow-to-red color change due to the deprotonation of the thiourea. 

Indicator-displacement assay [90] is an effective method that allows optical anion detection with optically inactive receptor. If a colorimetric or 

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Other neutral heterocyclics can be bound within these molecular receptors provided that appropriate matching of functionality is arranged. For example, the acridine 8 can form cooperative hydrogen bonds with cyclic diamides such as primidone 14, whereas its diamide derivative 15 provides an ideal microenvironment for diketopiperazines [16] (Scheme 8). A variety of heterocycles of differing size, shape and functionality were used to delineate the promiscuity of the synthetic molecular clefts. 

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