Synthesis of novel calixcrown derivatives with selective complexation towards cesium ions

A series of novel calix[4]arenecrown-6 derivatives with an alkenyl loop of various sizes 5-8 were synthesized via intramolecular ring closing olefin metathesis and characterized by ~1H NMR,~（13）C NMR and ESI-HRMS.Their complexation property towards cesium ion was studied by ^1H NMR technique.Two-phase extraction of alkali metal ions using UV-vis spectroscopy revealed remarkably different extractabilities.These results indicate that the complexation capacities towards cesium ions can be tuned and controlled through cooperative regulation of the strain of the loop and conformational change of calixcrown skelton.