INTERACTIONS BETWEEN METAL-CATIONS AND THE IONOPHORE LASALOCID .12. ALKALINE-EARTH LASALOCID 1-2 COMPLEX SALTS IN CHLOROFORM - FORMATION AND STRUCTURE

Extraction of alkaline-earth cations M2+ in water by lasalocid HA in chloroform results in formation of neutral complex salts MA2. Corresponding reaction constants are obtained. An increase in the selectivity of lasalocid as a function of cation size is observed. A systematic investigation of the structure in chloroform of the species formed with all the alkaline-earth cations is carried out using H-1 and C-13 NMR spectroscopy. The two anion ligands consistently play a strongly dissymmetric role but significant structure variations are observed according to the cation involved, coordination sites, respective location of the two ligands, and rate of exchange between them. Data on lasalocid-divalent cation interaction processes in water-membranes, either natural or model, are tentatively related to these findings.