Electrochemical sensing of F− and Cl− with a boronic ester-functionalized polypyrrole

The anodic electropolymerization of pyrrole 3 substituted by a pinacolborane moiety 1 yielded anion-sensitive conjugated polymer films. The effect of different halides (F−, Cl− and Br−) on the voltammetric response of poly(1) was examined in organic and hydro-organic media. Larger effects were observed in CH2Cl2 because of a weaker solvation of anions. In this solvent the system corresponding to the doping/undoping of poly(1) was shifted 450 and 175 mV towards less oxidizing potentials in the presence of F− and Cl−, respectively. In contrast, the polymer response was unchanged upon the addition of Br−. These results were consistent with a greater affinity of the immobilized boronic ester groups for F−, which could be explained by the hardness of the Lewis base.