Guest ditopic

A related anthracene-based ditopic sensor (11.28) has been constructed, which can recognise diammonium cations along the same lines as 3.103 (Section 3.12.3). Use of the anthracene-derived group as a spacer as in 11.27 gives fluorescent recognition of 11 N1 (Cl I NI I3+ guests as a function of spacer length.20... 

Scheme 7.13 Self-assembly of ditopic container 54 and inclusion of guests (alkylammonium salts).

The potential of ditopic cavitand complexes to bind ditopic guests has been demonstrated by Rebek and coworkers using cavitand 53 as monodentate ligand (Scheme 7.13) [58]. Cavitand 53 combines the advantages of a deep vase-like cavity obtained through a network of hydrogen bonds and the presence of a tolylpyridyl group able to coordinate to the metal center. The ditopic complex 54 forms quanti-... 

The recognition of different re-donating arene guests with a common re-accepting host has been subjected to control by metal ion crown ether recognition in the next case history to be described. The 18-crown-6 derivative 18, which bears a DNP ring system [12], is a ditopic compound that can act (Figure 11) as a host for alkali metal (e.g., K+) cations as well as as a... 

Di- and polytopic host-guest systems have provided a convenient starting point for the construction of larger assemblies and many systems of this type are now known. For example, in an early study Kimura et synthesised the catecholamine complex 17. The crown ether unit of this ditopic host was known to be an effective receptor for primary alkyl ammonium salts, whereas the partially protonated form of the hexamine ring had been documented to bind anionic substrates (such as car-boxy lates) or electron-donor substrates (such as catechols). Accordingly, this host forms stable 1 1 complexes with zwitterionic guests such as amino acids, pep-... 

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