Toward isolated molecular wires: A pH-responsive canopied polypyrrole

The design, synthesis, and electropolymerization of sterically hindered pyrrole derivatives are described. Endo and exo adducts of cyclopentadiene and N-phenylmaleimide were converted to give bicyclo[2.2.1]heptane-fused pyrrole monomers, in which a phenyl group is rigidly placed proximate the pyrrole fragment. Oxidative polymerization of these monomers affords highly conductive polypyrroles. The rigid molecular scafffold of the pyrrole monomers limits cross-communication between adjacent conducting strands and produces a defined narrow potential window of high conductivity dominated by intrachain polaronic charge carriers. The resultant loosely packed polymer chains allow for superior sensory properties. Notably, the electrical conductivity of oxidatively doped poly(7) could be reversibly modulated in aqueous electrolytes at pH 3-9.