Crystallization of cesium complex containing bis(2-propyloxy)calix[4]crown-6 and bis[(trifluoromethyl)sulfonyl]imide

A complex of Cs+ with the calixcrown bis(2-propyloxy)calix[4]crown-6 (BPC6) and bis[(trifluoromethyl)sulfonyl]imide (NTf2−), an anion of ionic liquid (IL), was crystallized in the interface region between n-octanol and water. The compound was characterized by single crystal X-ray diffraction, ESI-MS, FT-IR, TGA and PXRD. Cs+ is coordinated with BPC6 by both the six oxygen atoms of the crown and the cation–π interactions, and with the anion NTf2− via one oxygen atom of the sulfonyl group. This single crystal explains the good extraction ability of BPC6 to Cs+ and reflects a coordinating interaction of NTf2− with the deficient complex [Cs·BPC6]+ during the extraction with an IL as diluent.