Silver Ion Inclusion by Calix[4]arene Ethers

Tetra-O-alkylcalix[4]arenes are shown to act as hosts for the Ag⁺ ion primarily through;π-arene—silver(I) complexation. The structure of one silver(I) complex has been determined by an X-ray structure analysis. The silver ion is held in the cavity of the calixarene and is weakly coordinated to two arene groups and one methoxy group. The calixarene is in the partial cone conformation. This conformation also predominates in solution. Variabletemperature NMR studies show that the silver ion can influence both the distribution and the rate of interconversion of the calixarene conformers compared to the free ligands, by locking the calixarene in the partial cone conformation. The interaction between the included silver ion and tetra-O-alkylcalix[4]arene is weak, and the silver ion can be displaced easily by other ligands, such as MeCN, alkenes, and alkynes.