Conductance study of complexation of ammonium and alkylammonium ions with some aza-substituted crown ethers in binary acetonitrile-dimethylsulfoxide mixtures

A conductance study of the interaction between ammonium and four different alkylammonium ions and dibenzodiaza-15-crown-4 (DBDA15C4), diaza-18-crown-6 (DA18C6), aza-18-crown-6 (A18C6) and dibenzyldiaza-18-crown-6 (DBzDA18C6) in acetonitrile-dimethylsulfoxide mixtures was carried out at 25degreesC. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data and, in the case of all cations used, found to vary in the order DBDA15C4 > DA18C6 > A18C6 > DBzDA18C6. In all cases, the substitution of alkyl groups on the ammonium ion is found to decrease the stability of the resulting macrocycles, complexes, the sequence of which being NH4+ > MeNH3+ > EtH3+ > Et2NH2+ > Et3NH+. The stability of all complexes in the binary mixtures used was found to decrease with increasing mole fraction of dimethylsulfoxide.