Study on the Supramolecular Interactions of p-Sulfonated Calix[4, 6, 8]arenes with Lomefloxacin

The supramolecular interactions between a homologous series of p-sulfonated calix[n]arenes (SCnA, n=4, 6, 8) as hosts and lomefloxacin (LFLX) were studied by spectrofluorometry. LFLX was found to react with SCnA to produce stable complexes. The fluorescence intensity of the complexes decreased gradually with increasing SCnA concentration. The formation of complexes was further confirmed by H-1 NMR studies and molecular modeling calculations. Data of the stability constants and thermodynamic parameters of the obtained complex showed that the stability of the SC8A-LFLX complex is superior to that of SC6A-LFLX and SC4A-LFLX. A mechanism was proposed to explain the inclusion process.