Novel Resorcinarene Cavitand-Based CMP(O) Cation Ligands: Synthesis and Extraction Properties

Tetrafunctionalized resorcinarene cavitands (4-6) have been synthesized starting from tetrakis(bromomethyl)cavitand 3. New cavitand-based cation ligands with (carbamoylmethyl)phosphonate (CMP) and -phosphine oxide (CMPO) moieties (8a,b and 9a,b) were prepared via two different routes in good (45-86%) overall yields. The ligands (8a,b and 9b) are very effective europium extractants. Ph(2)CMPON(Pr)-cavitand 8b has the highest extraction constant, determined with radiotracer experiments, for 1:1 complexation with Eu(picrate)(3) (K(ex)(1) = 2.7 x 10(12) M(-)(4)). The steric preorganization of the four CMP(O) moieties on the resorcinarene cavitand improves the efficiency and selectivity [of Eu(III) over UO(2)(II) and Fe(III)] of the metal extraction processes, compared to simple CMP(O) extractants.