Synthesis and extraction results of new halide terminated 2-alkyl-p-tert-butylcalix[4]arenes bearing phosphine oxides or ketones on the narrow rim

Abstract

The synthesis of lower rim tetraphosphorylated and tetraketone calix[4]arenes with haloalkyl groups tethered to a single methylene bridge and their utilization as extraction agents for rare earth elements are reported. Synthesis of these new functionalized calix[4]arene species has been achieved in good to modest yields, and extraction of nine lanthanide nitrates has been explored using these novel calix[4]arene species. The tetraphosphorylated calix[4]arenes show better lanthanide extraction efficiency than their ketone counterparts, especially for europium (III). These experiments demonstrate that inclusion of a substituent tethered to the methylene bridge does not significantly reduce the extraction efficiency of these new calix[4]arene ligands as compared to similar unsubstituted ligands in literature, making them important precursors in the development of functionalized stationary phases for separation of lanthanides. Development of similar CMPO-bearing narrow rims and new solid-phase extraction materials for the solid–liquid separation of lanthanides remains the subject of future work.