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

Abstract

The stability constants (β^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 ion- transfer 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 β^NB₁(M)-values using the equation log k^pot_LiNa=0.70+log[β^NB₁(Na)/β^NB₁(Li)], and the resultscompared with those previously described for other bis(8-quinolyloxy)propane derivatives.