Complexation of isoleucine by phosphorylated calix[4]arene in methanol followed by calorimetry, NMR and UV-VIS spectroscopies, and molecular modeling methods

Complexation of isoleucine with bis (dihydroxyphosphorylhydroxymethyl) dipropoxycalix[4]arene was studied by titration calorimetry, NMR and UV-VIS spectroscopies and in terms of molecular modeling. The experimental data allowed to infer the occurrence of two heterogeneous non-equivalent calixarene moieties complexed by a single isoleucine molecule. The association constants were calculated to be 25,000±3000 and 1700±300 for the (1:1) and (2:1) calixarene-isoleucine complexes, respectively.