Structural Effect of Several Acylic Neutral Carriers Containing 8-Quinolyloxy Units on the Stability Constants of Their Li⁺ Complexes in Water-Saturated Nitrobenzene

Y. Kudo, T. Miyakawa, Y. Takeda, H. Matsuda, and K. Hiratani
[Analytical Sciences, Vol.10, 1994]

The stability constants (beta^NB₁(M)/mol^-1dm³) of 1:1 complexes of M⁺(=Li⁺,Na⁺) with 1,3-bis (8-quinolyloxy) propane (IV),1,4-bis (8-quinolyloxy) butane (V) and 3,3-bis [(7-methyl -8-quinolyloxy) methyl]oxetane (VI) were determined by iontransfer polarography in water-saturated nitrobenzene (NB) at 25°C. Their logarithmic values were on the order of VI (4.6) < V (5.7) < IV (7.4) for M=Li and VI (3.9) < V (4.5) < IV (5.7) for M=Na. This order shows that the stability of the Li⁺ and Na⁺ complexes significantly increases when the carrier can form a four-coordinate structure similar to that of a tetradentate 14-crown-4 in their complexes. The potentiometric selectivity coefficients (k^pot_LiNa ) of IV-VI for Li⁺ against Na⁺ were calculated based on the beta₁^NB(M)- values using the equation log k^pot_LiNa=0.07+log[beta₁^NB(Na)/ beta₁^NB(Li)], and the results compared with those previously described for other bis (8-quinolyloxy) propane derivatives.