Templates hydrogen-bonding properties

Apart from the successful imprinting discussed above, the recognition for many templates is far from that is required for the particular application, even after careful optimization of the other factors affecting the molecular recognition properties. Often, a large excess of MAA in the synthesis step is required for recognition to be observed and then only in solvents of low to medium polarity and hydrogen bond... 

Since Pedersen s original work on the use of cations to template the formation of crown ethers [18-20], a large number of different templating agents for macro-cyclization reactions have been reported. While the initial work concentrated on the use of metal cations, further developments demonstrated that species with hydrogen bonding donor or acceptor properties could be equally useful to template the synthesis of macrocyclic molecules. 

Fullerene stoppers have also been introduced in rotaxanes as a way to probe the motion of the ring thanks to their well-defined photophysical and electrochemical properties.54 In the rotaxane shown in Scheme 9.12, the hydrogen bonding station (a glycylglycine template) was placed far away from the fullerene by a triethylene glycol spacer.55... 

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