Abstract: | Potentiometric and cyclo-voltammetric studies have been carried out on monensin anion (Mon–) complexes with the alkali ions as well as with Tl+ and Ag+ in absolute methanol solutions. The log Kf values obtained for the complexity constants and corrected for the activity effects are: Li+, 3.3±0.1; Na+, 6.72±0.05; K+, 5.18±0.05; Rb+, 4.58±0.05; Cs+, 3.75±0.05; Tl+, 5.31±0.05; Ag+, 8.2±0.2. It is seen that for the alkali, the most stable complex is formed with Na+. The enthalpy and entropy of complexation with the sodium ion were found to be Ho=–5.47±0.24 kcal-mole–1 and So=+12.4±0.7 e.u. The complex, therefore, is enthalpy and entropy stabilized. |