Salen like metal binding

Relatively simple reagents containing a salen -like metal binding unit with protonatable pendant tertiary amine groups to accommodate the sulfate dianion have been developed to establish proof-of-concept,[82] and the incorporation of the metal cation in the salen cavity has been shown to template the sulfate-binding site and enhance extraction (Figure 10). [83]... 

The Lewis-acidic uranyl dication, UOi, center has been used by Reinhoudt and his group to build up receptors based on uranyl-salen complexes and crown ether units, 12. In particular, the two benzo[15]crown-5 units form a sandwich-like complex with potassium while the metal binds to the dihydrogen phosphate counterion. ... 

---