Differential pulse polarographic studies of mercury complexes with some crown ethers in nonaqueous solvents

The complex formation of Hg 2+ with some macrocyclic crown ethers in nitrobenzene, acetonitrile and dimethylformamide solutions was studied by differential pulse polarography at 25°C. The stoichiometry and stability of the complexes were determined by monitoring the shift in the Hg 2+ differential pulse peak potential against the ligand concentration. The stability of the resulting 1:1 complexes vary in the order dicyclohexyl-18-crown-6 > 18-crown-6 > 15-crown-5 > dibenzo-18-crown-6 > dibenzo-24-crown-8 > benzo-15-crown-5 > 12-crown-4. There is an inverse relationship between the complex stability and the Gutmann donor number of solvents.