Ferrocene polyaza coronands and cryptands

Polyaza ferrocene coronands with three, four, and five nitrogen atoms in the macrocycle, 46 [97, 98], have been prepared and investigated. They form nickel(II) host-guest complexes, and reversible oxidation of the ferrocene moiety can be 

A more sophisticated structure incorporating a 1,1-bipyridyl fragment, 47, can coordinate as an exo receptor through its external coordination sites it is remarkable because of its high selectivity for Cl relative to H2P04 [99]. 

A novel redox-active cryptand, 48, containing two bipyridyl and two ferrocene units incorporated in a macrocycle has been recently described [100, 100a]. 

A remarkable cryptand, incorporating three ferrocene moieties connected by two tripodal tetramine fragments, 49, has been reported [101]. 

A less traditional nitrogen-containing ferrocene coronand is the phosphorus-nitrogen macrocycle 50, which binds anions by hydrogen-bond interactions and is selective for H2P04 against HS04 and Cl anions in dichloromethane solution [102]. 

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