Synthesis and Alkali Metal Ion Binding Properties of Two Rigid Sterochemical Isomers of Calix[6]arene Bis-crown-4

摘要: Cone and 1,2,3-alternate stereochemical isomers of 37,40-diallyloxy-(38,42),(39,41)-bis-crown-4 calix[6]arene, 3 4 were isolated in moderate yields by bridging the dialkylated calix[6]arene 2 with triethylene glycol di-p-tosylate. The alkali metal complex stoichiometries, association constants, ion selectivities studied 1H NMR titration experiments, liquid−liquid extraction, electrospray ionization mass spectroscopy, X-ray crystallography. Good agreement between gas-phase solution-phase studies regarding these binding properties was observed. Both conformers formed 1:1 complexes all ions but structurally preorganized such that each exhibited a strong preference for larger cesium as evidenced “deep-cavity” host 4, wherein π-metal interactions helped to stabilize complex. Cs+/Na+ selectivity factor found be 1500, while only 140.