First Application of Calixarenes as Extractants in Room-temperature Ionic Liquids

We synthesized a calix[4]arene bearing pyridine, which has a similar molecular structure to the constitutional unit of 3-methylimidazolium hexafluorophosphate-based room-temperature ionic liquids. The pyridinocalix[4]arene was found to be soluble in ionic liquids, and this compound showed 230-fold extractability in ionic liquid over that in chloroform for silver ions.