Cobaltabisdicarbollide anion [CO(C2B9H11)(2)](-) as doping agent on intelligent membranes for ion capture

It has been proven that the non-nucleophilic, low charge density and weakly coordinating cobaltabisdicarbollide anion [Co(C2B9H11)(2)](-), can be highly relevant as dopant for conducting organic polymers. We have developed a new material based on polypyrrole (PPy) which uses the cobaltabisdicarbollide anion as a doping agent. This anion provides enhanced properties to PPy, the most striking one is the high over oxidation resistance. The high volume of [Co(C2B9H11)(2)](-) imposes low mobility inside the polymeric matrix thus preventing dopant leakage when a reducing potential is applied on the material. Under these conditions the cation capture (Eq. 1) prevails during the reversible electrochemical redox process, also called doping-undoping. [PPyn+ (A(-))(n)]+nC(+)+ne(-)Delta[PPy(A(-))(n)(C+)(n)]. The membrane is highly sensitive to the cationic volume of the solute. This property has allowed to develop cationic selective membranes by control of the applied reducing potential. The chronocoulometries registered during the charge-discharge process show an almost perfect reversibility of cation exchange process and no detectable degradation of the membrane due to dopant loss or over oxidation even after 40 successive cycles. (C) 2002 Elsevier Science B.V. All rights reserved.