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

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.

New 2-substituted haloalkyl tetraphosphorylated and tetraketone calix[4]arenes were synthesized and used to understand the effect on extraction of lanthanide ions in comparison to known literature. With distinct selectivity for europium and differential affinity for metals across the lanthanide series, these new ligands should prove to be useful precursors for the development of solid phase extraction materials.