A Lipophilic Derivative of Vitamin B₁₂ as Selective Carrier for Anions

Incorporation of the lipophilic Co(III)‐cobyrinate octadecyl‐cobester 1 and of its ionic aqua‐cyano perchlorate derivative 2 into poly(vinyl chloride)/bis(1‐butylpentyl) adipate liquid membranes induces a selectivity, measured potentiometrically, of about 10 3 for SCN − an NO with respect to CI − , but only of about 4 for ClO vs. CI − . This is in contrast to classical anion‐exchanger membranes, which exhibit a selectivity sequence ClO > SCN − ≫ NO > Cl − in accordance with the Hofmeister , series. The Co(III)‐corrins 1 and 2 , when components in solvent polymeric membranes, undergo exchange of axial ligands an behave as highly selective carriers fof SCN − and NO .