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 c hloroform results in formation of neutral complex salts MA2. Correspon ding reaction constants are obtained. An increase in the selectivity o f lasalocid as a function of cation size is observed. A systematic inv estigation of the structure in chloroform of the species formed with a ll the alkaline-earth cations is carried out using H-1 and C-13 NMR sp ectroscopy. The two anion ligands consistently play a strongly dissymm etric role but significant structure variations are observed according to the cation involved, coordination sites, respective location of th e two ligands, and rate of exchange between them. Data on lasalocid-di valent cation interaction processes in water-membranes, either natural or model, are tentatively related to these findings.