Ion-transfer-polarographic study of distribution equilibrium of metal complex cations with several crown ethers between nitrobenzene and water

• Published in: BUNSEKI KAGAKU Vol. 40; no. 11; pp. 779 - 784
• Main Authors: TAKEDA, Yasuyuki, KUDO, Yoshihiro, MATSUDA, Hiroaki
• Format: Journal Article
• Language: Japanese
• Published: The Japan Society for Analytical Chemistry 05.11.1991
• Subjects: distribution constants of crown ether complxes; ion-transfer polarography; sodium ion selectivity coefficients; stability constants; water/nitrobenzene interface
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.40.11_779

Transfers of Li+, Na+ and K+ at a water/nitrobenzene(w/NB) interface facilitated by 15-crown-5(15C5) and benzo-15C5(B15C5) were examined ion-transfer-polarographically at 25°C. The stability constants (βNB1) of the 1:1 complexes of the metal ions (M +) with 15C5 and B15C5 in the NB-phases were obtained from the metal ion-concentration dependence of the half-wave potentials. The distribution constants (KD, ML) of the metal-complex cations ML z+ (z =1, 2) with L=15C5, B15C5 and 18-crown-6(18C6) derivatives, in which the fir-values of the complexes with 18C6 derivatives were reported before, were calculated from KD, ML=KD, LKD, MβNB1(M)/βW1(M)=KD, L×KM/ML/βW1(M), where KD, i and β W1(M) denote the distribution constants of species i (i=ML, L, M) between the w- and the NB-phases and the stability constants of MLz+ in the w-phase, respectively. The values of log KD, ML were small when the coordination numbers of water molecules coextracted with MLz+ into the NB-phase were large. The logarithmic values of the potentiometric selectivity coefficients, which were expressed by logkpotNaM'=log(KM'/M'L/KNa/NaL), of Na+ against M'z+ were also estimated.