Transition based anion receptors, hydrogen bonding

Another interesting and potentially very useful group of calixarene-based anion receptors is represented by systems with appended transition metal complexes of 2,2-bipyridine units. Technically, these systems utilise classical hydrogen bonding interactions of amidic/urea functions hence, from this point of view, they do not differ from many other receptors. On the other hand, the covalent attachment of bipyridine complexes of ruthenium(II) or rhe-... 

The Perez group has also synthesized a range of d transition metal-derived anion receptors based on rhenium and ruthenium, for example, complexes 137 and 138. Compound 137 contains a bidentate pyrazolylamidino ligand which provides one NH hydrogen-bond donor and an additional pyrazolyl NH donor. The complex binds chloride particularly strongly because of its rigid nature, with... 

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