Analysis of ion association reactions between monovalent polycyclic aromatic cations and anions in aqueous solution as studied by capillary zone electrophoresis

Article abstract of DOI:10.1246/bcsj.73.669

Ion association reactions between monovalent polycyclic aromatic cations and anions have been studied through the mobility change in capillary zone electrophoresis. When the cationic reagent possessing aromatic moieties was used, isomers of aromatic anions were well resolved. Apparent electrophoretic mobility of the anions decreased with an increase in the concentration of the cationic reagent in the migrating solution; the magnitude of the decrease was large when bulkier cations were used. The ion association constants obtained by analyzing the mobility change increased with an increase in the number of aromatic rings of either the pairing cations or the anions. The ion associates formed consist of monovalent cations and anions, and the ion association constant for an ion associate formed between 1- propylbenzo[f]quinolinium ion and pyrene-1-carboxylate ion was in the magnitude of 10^2.74 dm³ mol^-1. Such ion associability was interpreted from the contribution of the stacking of aromatic moieties in an aqueous solution, in addition to the increase in the hydrophobicity.