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

133Cs NMR spectroscopy was used to determine the stoichiometry and stability of the Cs+ ion complex with dibenzo-21-crown-7 (DB21C7) in acetonitrile-dimethylsulfoxide (96.5:3.5, w/w) and nitromethane-dimethylsulfoxide (96.5:3.5, w/w) mixtures. A competitive 133Cs NMR technique was also employed to probe the complexation of Na+, K+, Rb+, Ag+, Tl+, NH4+, Mg2+, Ba2+, Hg2+, Pb2+ and UO22+ 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+ ≈ Ba2+ > Tl+ > Cs+ > NH4+ ≈ Pb2+ > Ag+ > UO22+ > Hg2+ > Mg2+ > Na+.