Anion recognition by cobaltocenium receptor molecules

A first venture into this field was to utilize the pH-independent, positively charged, redox-active cobaltocenium moiety (Beer and Keefe, 1989 Beer et 

To test this hypothesis further, simple acyclic cobaltocenium derivatives (Fig. 38) containing tertiary amide groups ([72] and [73]) were prepared and complexation with Cl- and Br anions was investigated in solution by nmr spectroscopy. No shifts of the host s proton resonances were observed, emphasizing again the importance of the amide N—H group in anion binding. 

The cathodic shifts of the redox potentials of compounds [68], [69] and [71] on addition of halide anions are due to the stabilization of the cobaltocenium cation by the bound anion which causes the redox couple to shift to a more 

New monosubstituted cobaltocenium derivatives functionalized with hydrogen-bonding amine groups (Fig. 39) have been prepared and the 

The crystal structure of the bromide complex of [78] has been elucidated and clearly shows bromide anions hydrogen-bonded to the amide N—H groups and, interestingly, also to the cyclopentadienyl hydrogen atoms (Fig. 40). 

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