LIQUID-LIQUID-EXTRACTION OF TRANSITION-METAL IONS WITH MACROCYCLIC SCHIFF-BASES CONTAINING PHENOL OR THIOPHENE SUBUNITS

Two types of macrocyclic Schiff bases containing either thiophene or phenol subunits were synthesized and the effect of ligand atoms on the liquid-liquid extraction of bivalent transition metal ions was studied. The phenol groups in the macrocycle led to a large increase in the extraction of transition metal ions. The least stable manganese(II) complex was extracted quantitatively into nitrobenzene as an ion pair with tetraphenylborate ion at pH 9. Copper(II) was selectively extracted from weakly acidic media, permitting its separation from manganese(II), cobalt(II), nickel(II) and zinc(II). The composition of extracted copper(II) species was evaluated. The extractability of metal complexes with a cyclic tetraaza Schiff base has been compared with that of the corresponding acyclic Schiff base.