Bifunctional receptors

Studies in the area of electrochemical molecular recognition deal with bifunctional receptor molecules that contain not only binding sites but also one or more redox-active centres whose electron transfer reaction is coupled to the receptor s complexation. Such systems can be described by the scheme of squares as shown in Scheme 1. 

A bifunctional receptor constructed by coupling two crown ether fragments to a UO2-salen complex has been reported for the simultaneous complexation of anions and cations [69]. This compound, shown in Figure 49, showed high selectivity in binding potassium dihydrogen phosphate. Selectivity of the membrane transport of H2PO4" (over Cl ) has also been shown [70]. 

Scanning the Proteome for Targets of Organic Small Molecules Using Bifunctional Receptor Ligands... 

We synthesized receptors 26 and 27 which consists of both a uranyl containing salen part for the complexation of the anion and a crown ether or a calix[4]arene tetraester based ionophore for the complexation of the cation [ref 33]. They have been prepared from the corresponding disaldehydes, cw-l,2-diaminocyclohexane and U02(0Ac)2 2H20 in refluxing alcohol. The complexation of the bifunctional receptors with cations and with anions was investigated by NMR spectroscopy, cyclic voltammetry, FAB-spectrometry, and liquid-liquid extraction experiments. 

Previously we reported that neutral metalloclefts and metallomacrocycles containing both an immobilized Lewis acidic U02-center and amido C(0)NH units as additional binding sites are excellent receptors for anions with a high selectivity for dihydrogen phosphate H2P04" [23,24]. By combination of anionic and cationic binding sites in one molecule, a bifunctional receptor can be obtained which is able to complex... 

Fig. 28.5 Binding modes of pyrene-appended bifunctional receptors 12 and 15...

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