Potentiometric Study of Thermodynamic Parameters of Complexing of Lithium Ion–Basic Aprotic Solvents and Sodium Ion–Macrocyclic Polyethers in Acetonitrile

Formation constants of the 1 : 1 complexes of lithium ion in acetonitrile (AN) with DMF, DMSO, DMA, and HMPA and of sodium ion in AN with 15-crown-5 (15C5), 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6), and cryptand 211 (Cryp 211), were determined at 10, 25, and 40 °C by potentiometric methods with a cationsensitive glass electrode. From the change of the formation constants with temperature, thermodynamic parameters ΔG298°, ΔH298° and −TΔS298°, were obtained. ΔG298°, ΔH298°, and −TΔS298° all in kJ mol−1, for Li+-solvent complexes were, respectively, −7.9, −9·0, +1·1 for DMF, −9.7, −10·1, +0·5 for DMSO, −10.0, −9·9, −0·1 for DMA, and −18.9, −15·8, −3·1 for HMPA, and those for Na+-macrocyclic polyether complexes, −28.4, −24·1, −4·5 for 15C5, −27.2, +1·6, −28·7 for 18C6, −28.6, −14·3, −14·2 for DB18C6, and −51.9, −53·8, +2·1 for Cryp 211. Some features about the roles of enthalpy and entropy terms in complexing have been discussed.