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

Abstract

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 (C₂ to C₄) 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 into 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.