ION-PAIR EXTRACTION OF LITHIUM ION BY A WATER-SOLUBLE PORPHYRIN

The equilibrium of ion-pair extraction of lithium porphyrin [octabromo porphyrin: o-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, H(2)obtp ps(4-); H2P4-] with tetrabutylammonium ion (X+) was studied at 25 degr ees C and I = 0.1 (NaCl, NaOH). Extraction and dissociation constants of the ion-pair complexes of free base porphyrin, deprotonated porphyr in and lithium porphyrin, defined as K-ex(H2P) = [X4H2P](o)/[H2P4-](a) [X+](a)(4), K-ex(HP)' = [X5HP](o)/[HP5-](a)[X+](a)(5), K-ex(LiP)'' = [ X5LiP](o)/[LiP5-](a)[X+](a)(5), K-dis(H2P) = [X3H2P-](o)[X+](o)/[X4H2P ](o) and K-dis1(LiP)'' = [X4LiP-](o)[X+](o)/[X5LiP](o), were determine d. These values were found to be K-ex(H2P) = (9.5 +/- 1.5) X 10(13) (m ol(4) dm(12)), K-dis1(H2P) = (3.5 +/- 0.7) X 10(-7) (mol dm(-3)), K-ex (HP)' = (4.7 +/- 0.4) X 10(16) (mol(-5) dm(15)) and K-ex(LiP)'' K-dis1 (LiP)'' = (8.4 +/- 0.7) X 10(12) (mol(-4) dm(12)), respectively.