Molecule-receptor binding sensor components

The Re(I) bipyridyl unit has been exploited in another series of ion-pair sensors. Molecules 61-64 incorporate crown ether components to act as cation receptors [43,44]. H NMR titrations revealed 61-64 to be selective for acetate over chloride. In all the receptors (except 62 and 64 with acetate) enhanced binding was observed in the presence of K+ cations. The degree of enhancement is lower in the xylyl-spaced molecules 62 and 64 (40-50%) than in 61 and 63 (80-110%). It is also small compared to that seen in the calix[4]arene receptor 60. 

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