Catalysis anion receptor molecules

The development of anion coordination chemistry and anion receptor molecules has opened up the possibility to perform molecular catalysis on anionic substrates of chemical and biochemical interest, such as adenosine triphosphate. The catalysis of phosphoryl transfer is of particular interest, namely in view of the crucial role of such processes in biology and of the numerous enzymes that catalyse them. 

M. W. Hosseini, A. J. Blacker, and J.-M. Lehn, Multiple molecular recognition and catalysis, nucleotide binding and ATP hydrolysis by a receptor molecule bearing an anion binding site, an intercalator group, and a catalytic site, J. Chem. Soc., Chem. Commun. 596(1988). 

In supramolecular chemistry, molecular recognition has evolved over the last 35 years and now much effort is directed towards the complexation of anionic [28], zwitterionic [29], ion-pairs [30] and neutral guests for various purposes, including catalysis [31[. Host molecules can be constructed covalently, or they can themselves also be assembled in a supramolecular fashion. This strategy, called receptor site self-assembly, has been exploited in recent years. Especially, dynamic host formation in the presence of a substrate is highly interesting [32]. 

As macrocyclic chemistry has developed, the variety and scope of the applications of these molecules have continued to multiply. This concluding section is an attempt to provide an overview of only three of the applications of synthetic macrocycles. A particularly insightful treatment can be found in the Nobel Lecture of Jean-Marie Lehn, which describes the concept of supramolecular chemistry from simple recognition, to cation and anion receptors, multiple recognition, catalysis, transport, and molecular devices. 

However, Lewis acid sites not only modify the Bronsted acid sites. These species will also act themselves in various ways in molecular sieve catalysis. Together with the adjacent framework oxygen atoms, Lewis acid sites will act as Lewis acid-base pairs, and may polarize bonds in reacting molecules, possibly enhancing their chemical reactivity [27,28]. For molecules that are already polar, this polarization could also be sufficient to catalyze a chemical transformation, e.g., in the reaction of alcohols [51]. Lewis acid sites also act as hydride or anion receptors in a variety of reactions. Thus, in most cases the character of an acid-base pair site will be more pronounced in the case of Lewis than in the case of Bronsted acid sites [52,53]. 

Owing to the popularity and vast modularity of the copper(l)-catalyzed azide-alkyne cycloaddition (CuAAC) [4,5], so-called click chemistry [24] (Fig. 1), many more 1,2,3-triazole-based anion receptors have been reported during the past 3 years (2008-2011). Reviews [25, 26] have been published to cover this new moiety in anion receptor chemistry. Therefore, this chapter will focus on triazole-based anion receptors that have not been reviewed to date. In addition, applications including sensors, ion-selective electrodes, catalysis, anion transport, and anion regulation, as well as their use in interlocked molecules, will be discussed. 

The ability of 1,2,3-triazole to bind anions with a C-H hydrogen bond is covered in Chap. 3, Binding Anions in Rigid and Reconfigurable Triazole Receptors by Lee and Hood. Applications including sensors, ion-selective electrodes, catalysis, anion transport and anion regulation, as well as their use in interlocked molecules, are discussed. 

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