First Synthesis of 1,3-Alternate 25,27-Dialkyloxy-5,17- diarylcalix[4]arenes-crown-6 as New Cesium Selective Extractants by Suzuki Cross-coupling Reaction.

The synthesis of new 25,27-dialkyloxy-5,17-diaryl-calix[4]arenes-crown-61a-f in 1,3-alternate conformation by Suzuki cross-coupling reaction is reported. Their conformation was determined using ¹H, ¹³C, 2D NMR and ROESY analysis, and X-ray crystallography. Extraction experiments using a two-phase solvent method involving sodium, potassium or cesium picrate showed good extraction of the cesium cation. The X-ray crystal structures of 1,3-alternate 25,27-dipropoxy-5,17-diphenyl-calix[4]arene-crown-6 ether 1a and its cesium picrate complex were established. Solid-state data were used to determine the complexion behavior of these new ligands. The efficiency of calixarenes 1a-f for cesium ion extraction could be ascribed to the rigidity and flatness linkages caused by the aryl groups at the lower rim of the aromatic moieties in the calixarene skeleton. In addition, the introduction of these aromatic moieties in positions 5 and 17 enhanced the solubility of the metal complexes in organic media. [ABSTRACT FROM AUTHOR]