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 f our carbamoylmethylphosphine oxide (CMPO) groups as ligating functions on t he narrow rim is described. These are easily;prepared in 65-80% yield via a cylation of the corresponding fixed cone aminoalkoxy (C-2 to C-4) derivativ es with p-nitrophenyl (diphenylphosphoryl)acetate. Extraction studies of se lected lanthanides (La3+,. Eu3+, Yb3+) and thorium (Th4+) from 1 M HNO3 to CH2Cl2 show a strong increase of the percentage extracted (%E) with increas ing length of the spacer. Extraction of Am3+, La3+, Nd3+, Sm3+ and Eu3+ fro m (0.1-4) M HNO3 int o-nitrophenyl hexyl ether shows, in contrast to the wi de rim CMPO derivative, no decrease of the distribution coefficient for hig her concentrations of nitric acid.