Cation Complexation by Hybrid Calixarenes

As with the hosts mentioned earlier, other hybrid host molecules have been synthesised which combine the advantages of the rigid, readily available calixarene framework with the binding 

2000 for K+ over Na. In contrast, a smaller sodium-selective ionophore 3.130 has been developed, which has been incorporated into ion-selective electrodes. These devices demonstrate a remarkable reverse selectivity for Na over K+ with selectivity factors of up to 10 for both cone and partial cone isomers. 

Barbour, L. J., Ferdani, R., Hu, J. X., Lariat ether receptor systems show experimental evidence for alkali metal cation-Jt interactions , Acc. Chem. Res. 2002, 35, 878-886. 

Soft metal ions are not restricted to complexation by heteroatom donors. Their electron-rich nature and large, uncontracted orbitals allow some very interesting complexation behaviour with r-acid ligands at the boundary between supramolecular and organometallic chemistry. A large range of transition metals 

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