Complexation study of UO22+ ion with 18-crown-6, dicyclohexyl-18-crown-6 and dibenzo-18-crown-6 in binary nitromethane-acetonitrile mixtures by a competitive NMR technique using 7Li nucleus as a probe

Lithium-7 NMR measurements were used to determine the stability of 1: 1 Li+ complexes with 18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6) and dibenzo-18-crown-6 (DB18C6) in various binary nitromethane-acetonitrile mixtures. A competitive (LiNMR)-Li-7 of UO22+ technique was also employed to probe the complexation U-2(2+) ion with these crown ethers in the mixed solvents used. In all solvent mixtures, the stability of the resulting 1: 1 complexes was found to decrease in the order DC 18C6 > 18C6 > DB18C6. There is an inverse relationship between the complex stability and the amount of acetonitrile in the mixed solvents.