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 (carbamclylmethyl)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. Ph2CMPON(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 UO2(II) and Fe(III)] of the metal extraction processes, compared to simple CMP(O) extractants.