Inorganic anion receptors

As will be illustrated, the use of inorganic and organometallic chemistry has, in the past 10 years, enabled the development of a rich and exciting range of novel, functional anion receptors. Inorganic anion receptors can be usefully subdivided into four classes dependent on the bonding interactions responsible for anion binding ... 

The first ester functionalized cobaltocenium receptor (74) developed by us in 1989, was based solely on electrostatic interactions (as discussed earlier) (9, 186). It was therefore decided to append the cobaltocenium moiety with secondary amide functionalized arms . In this manner, the receptors became more resistant to hydrolysis (a recurrent problem with ester-based systems), and also incorporated neutral hydrogen-bond donors capable of coordinating anions. [An interaction between a secondary amide (acetamide) and the bromide anion was physically investigated (by IR spectroscopy) as long ago as 1961 (211)]. We made the first report of this novel type of receptor (91 and 92) in 1992 (212), which was, in fact, the first class of inorganic anion receptor that incorporated hydrogen-bonding functionalities. 

Polyammonium macrocycles and macropolycycles have been studied most extensively as anion receptor molecules. They bind a variety of anionic species (inorganic anions, carboxylates, phosphates, etc.) with stabilities and selectivities resulting from both electrostatic and structural effects. 

Beer, P. D. Smith, D. K. Anion binding and recognition by inorganic based receptors, Prog. Inorg. Chem. 1997, 46, 1-96. 

Otto S, Kubik S (2003) Dynamic combinatorial optimization of a neutral receptor that binds inorganic anions in aqueous solution. J Am Chem Soc 125 7804—7805... 

Anion Binding and Recognition by Inorganic Based Receptors... 

Dietrich s reviews have provided detailed accounts of early approaches to this type of anion receptor (4, 13). This chapter will, therefore, only briefly outline the basic types of organic receptors for anions as they will prove of relevance in understanding some of the recent inorganic systems that form the main body of discussion. 

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