Protonated polyammonium macrocycles, anion

Oxaazamacrocycles are molecules with combined crown ether and amino group properties for example, in dependence on the size of macrocyclic ring and the position of heteroatoms stable complexes with various metals can be formed [32]. Furthermore, when protonated, these compounds are excellent anion binders. In fully protonated polyammonium macrocycles, the coulom-bic attractions and hydrogen bond formation play a dominant role in the anion complexation. The receptors (R,R)-5 and (S,S,S,S)-6 were designed to bind dicarboxylates [33]. 

A method for the preparation of thin films of Fe4[Ru(CN)6]3 ( ruthenium purple ) involving electrochemical reduction of K3[Ru(CN)6] in a solution of Fe2(S04)3 has been developed.28 This ruthenium purple modified electrode is claimed to be one of the best catalysts for evolution of oxygen and chlorine. Electrochemical studies on polyammonium macrocyclic complexes of [Ru(CN)6]4 indicate a 1 1 stoichiometry with a monoelectronic, reversible, oxidation for these complexes this illustrates the control of redox potential of anions by complexation with appropriate receptor molecules.29 The kinetics of oxidation of [Ru(CN)6]4 by [Mn04] in HC104 have been investigated by stopped-flow techniques. It is found that [Ru(CN)6]4" is quantitatively oxidized to [Ru(CN)6]3 in accordance with equation (1) and that two protonated intermediates [RuH(CN)6]3 and [RuH2(CN)6]3 are involved in the oxidation process.30... 

Polyaza macrocycles in their protonated form, either full or partial, are able to interact with anionic species, by establishing noncovalent interactions (both electrostatic and hydrogen bonding). Complexation of anions by synthetic polyammonium molecules has been explored over the past two decades, and several examples of selective recognition of different anionic substrates have been reported [14 22], Some polyammonium macrocycles such as [24]aneN6H6 +, 16, and... 

Polyammonium macrocycles are successful mimics of a variety of phosphoryl transfer enzymes. These simple compounds are noted for their capability to bind to a number of anions, including the simple phosphate and polyphosphates as well as more complex nucleotides. "Large" polyazacycloalkanes in their protonated forms have been found to exhibit ATP binding as well as ATPase activity. A general accepted mechanism for ATP hydrolysis catalyzed by polyaza macrocycles involve the formation of a ATP-receptor complex, held by electrostatic interaction and hydrogen bonds, followed by the formation of a covalent intermediate macrocyclic-phosphoramidate species, which is subsequently hydrolyzed (see Figure 2)P... 

In a related study (78CC934,79HCA2763) Lehn and coworkers incorporated guanidinium groups into macrocycles (e.g. 29). The resulting polyguanidium salts form stable complexes in water with phosphate and carboxylate anions. Unlike polyammonium anion receptors, these species remain protonated over a wide pH range and hold considerable potential in the development of anion-selective electrodes. 

Protonation of these macrocycles occurs readily, even in water in absence of added acid, yielding polyprotonated species which are well suited to the study of anion coordination. Particularly polyammonium cations have shown to be good receptors for anionic complexed species. 

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