Controlling the growth of conjugated polymers on electrode surface: synthesis, electropolymerization, and spectroelectrochemistry of conjugated bispyrroles

Abstract

Fluorescent bispyrroles 6-9 consisting of different aromatic bridging moieties were prepared and characterized. Detailed studies on the electropolymerization, cyclic voltammetry, and spectroelectrochemistry are reported. The electronic character of the bridging moieties and the solubility inducing hydrocarbon side chains play crucial roles in controlling the growth of the polymer film on the electrode surface. The bispyrroles with divinylbenzene and divinylnaphthalene bridging groups react under film formation while the corresponding divinylanthracene-bridged bispyrrole show reversible formation of the dication 9²⁺ exhibiting a "two-electron-one-wave" feature. Presence of alkoxy substituents on the divinylbenzene moiety is shown to have adverse effect on the electropolymerization. The role of the bridging moieties in controlling the film growth on the electrode surface is rationalized on the basis of the orbital coefficients at the C^α-positions of the pyrrole moieties, which in turn are determined by the electronic nature of the conjugation bridge.