Synthesis and electrochemistry of carboranylpyrroles. Toward the preparation of electrochemically and thermally resistant conjugated polymers

Pyrrole derivatives covalently linked to a neutral ortho- or anionic nido-carborane cage via a methylene or ethylene spacer arm have been synthesized. Their electrochemical study showed that only the neutral compounds yielded anodically conducting 3-substituted polypyrrole films. In contrast, the anodic oxidation of the anionic derivatives underwent the passivation of the electrode surface. The pyrrole with a two-carbon linkage was the most efficiently electropolymerized, and the relevant polymer films exhibited the best electroactive and conducting properties. These were resistant to highly positive potentials owing to the hydrophobic nature and the electron-withdrawing character of the attached carborane cage. Moreover, this material was more thermally stable than unsubstituted polypyrrole.