Calix[4]arenes with CMPO functions at the narrow-rim.: Synthesis and extraction properties

The synthesis of three new derivatives of tert-butylcalix[4]arene bearing four carbamoylmethylphosphine oxide (CMPO) groups as ligating functions on the narrow rim is described. These are easily;prepared in 65-80% yield via acylation of the corresponding fixed cone aminoalkoxy (C-2 to C-4) derivatives with p-nitrophenyl (diphenylphosphoryl)acetate. Extraction studies of selected lanthanides (La3+,. Eu3+, Yb3+) and thorium (Th4+) from 1 M HNO3 to CH2Cl2 show a strong increase of the percentage extracted (%E) with increasing length of the spacer. Extraction of Am3+, La3+, Nd3+, Sm3+ and Eu3+ from (0.1-4) M HNO3 int o-nitrophenyl hexyl ether shows, in contrast to the wide rim CMPO derivative, no decrease of the distribution coefficient for higher concentrations of nitric acid.