Anion template

Scheme 28 The templating anion determines the orientation of the threads in the pseudoro-taxane, which has important consequences for the solid-state structure of these assemblies...

Another use of the DNA-lipid complex was reported by Wong and coworkers [33]. The DNA molecule structural features can be imprinted into CdS nanostructures by using self-assembled DNA-membrane templates. The initial application of the DNA-lipid multilamellar structure was the use as gene carriers in gene therapy, and many reports [34-39] were published (Fig. 6b). To prepare the DNA templates, anionic DNA was reacted with a mixture of... 

Nonetheless, much excellent use has been made of this system. Receptor 5, for example, extracts p-nitrobenzoate quantitatively from water into chloroform (43), and the chirality of the receptor allows the possibility of chiral anion recognition (44). Guanidinium has also been incorporated into devices, such as a hydrogen sulfite selective electrode (45). Recently, Mendoza and co-workers (46) reported a chiral double helical array of polyguanidinium strands assembled around sulfate templating anions, the first anion centered helical structure. 

Figure 8. Templating anions used in the synthesis of macrobicyclic receptor 83. Receptor yields are quoted, as are shifts of the NMR peaks for the included anion. Receptor yield quoted under conditions of more concentrated guest. ea = axial proton, e = equatorial proton. AS could not be analyzed due to signal overlap. Not complexed (no upheld shift of guest protons). [Reprinted with permission from M. Fujita, S. Nagas, and K. Ogura, J. Am. Chem. Soc., 117, 1649 (1995). Copyright 1995 American Chemical Society.]...

A rare example of electropolymerisation employed for the formation of an anion selective crosslinked polymer matrix was introduced by Kamata et al. [153,154]. Reductive coupling between trifunctional p-cyanopyridinium crosslinkers (Fig. 15) in water containing the required counteranion led to stable polymer networks which showed thermodynamic and kinetic anion selectivity. A size exclusion effect was observed whereby only the imprint halogen (and any smaller halogen anion) was electrochemically recognised. Diffusion of the counterion was reduced in the case of the same template anion MIP, but increased with the size of the templating anion. Experiments clearly demonstrating anion selectivity have yet to be carried out. 

As an example, chloride has been shown fo be an effective template for the preparation of macrocycles incorporating heterocycles, and where the templating anion is generated in the course of the reaction. In the case of the macrocycle incorporating two imidazolium moieties and one triazole residue (Scheme 2), the yield of the product was shown to depend critically on the precursors used for the reaction. When a bis-imidazole incorporating triazole as a spacer was used with mefa-dichloroxylylene, the yield of the reaction was never >20% even in the presence of additional chloride ions. On the other hand, when a bis-imidazole with a mefa-xylylene spacer was used with bis-chloromethyl-triazole, the yield was 50%. In the presence... 

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