Competitive cesium-133 NMR spectroscopic study of complexation of different metal ions with dibenzo-21-crown-7 in acetonitrile-dimethylsulfoxide and nitromethane-dimethylsulfoxide mixtures

(133)Cs NMR spectroscopy was used to determine the stoichiometry and stability of the Cs(+) ion complex with dibenzo-21-crown-7 (DB21C7) in acetonitrile-dimethylSLIlfoxide (96.5:3.5, w/w) and nitromethane-dimethylsulfoxide (96.5:3.5, w/w) mixtures. A competitive (131)Cs NMR technique was also employed to probe the complexation of Na(+), K(+), Rb(+), Ag(+), Tl(+), NH(4)(+), Mg(2+), Ba(2+), Hg(2+), Pb(2+) and UO(2)(2+) ions with DB21C7 in the same solvent systems. All the resulting 1:1 complexes in nitromethane-dimethylsulfoxide were more stable than those in acetonitrile-dimethylsulfoxide solution. In both solvent systems, the stability of the resulting complexes was found to vary in the order Rb(+) > K(+) - Ba(2+) > Tl(+) > Cs(+) > NH(4)(+) - Pb(2+) > Ag(+) > UO(2)(2+) > Hg(2+) > Mg(2+) > Na(+). (c) 2007 Elsevier B.V. All rights reserved.