Post-Overoxidation Self-Recovery of Polypyrrole Doped with a Metallacarborane Anion

Abstract

By using the metallacarborane [Co(C2B9H11)2]-, [1]-, as a doping anion, PPy materials can be made 300−500 mV more resistant to overoxidation. These materials are written as PPy/[A] to indicate a noncovalency between the anion and the PPy and have a clear overoxidation resistance limit, ORL, so that once this is surpassed the material becomes permanently nonelectroactive or dead. On the contrary if [Co(C2B9H11)2]- is chemically bonded to pyrrole through a spacer and then is copolymerized with pyrrole the resulting material, PPy−[1sp], has an electroactive behavior similar to PPy/[A] so that once an apparent ORL is reached the PPy−[1sp] becomes electroinactive but, very importantly, in few hours recovers the electroactivity. The situation is so attractive that even in the case that the overoxidation threshold was surpassed the system would react to restore itself. In this paper we demonstrate that [1]- not only enhances the overoxidation resistance but that, if grafted to the PPy strand, the applied voltage that can sustain the new material can go far beyond the overoxidation limit of the compositionally similar material with, however, no anion grafting. These properties are due to grafting of the metallacarborane to the PPy and have not been observed before. This behavior is not a consequence of the anion grafting to the PPy but depends on the nature of the anion.

Are the Accompanying Cations of Doping Anions Influential in Conducting Organic Polymers? The Case of the Popular PEDOT

“…The IR spectra of the polymers PEDOT:M[COSANE] do not show strong and sharp B−H bands, but a small and broad band. Previous studies have demonstrated that the metallacarborane with conducting polymers does not show strong and sharp B−H bands, but after the overoxidation of the polymer, a strong and sharp B−H band appears . Therefore, the small B−H band is characteristic of the metallacarborane as a doping agent of conducting polymers.…”

“…Metallacarboranes, of which cobaltabisdicarbollide, [Co(C 2 B 9 H 11 ) 2 ] − , denoted as [COSANE] − , is the most researched, are redox‐reversible highly stable species with large possibilities for functionalization. They have been utilized both as components of pendant arms and as doping agents with PPy– and in a prospective PEDOT polymer . Cobaltabisdicarbollide has been proven to form hydrogen and dihydrogen bonds, interacting with weakly acidic X−H units or lone‐pair elements, and can self‐assemble in water to generate micelles and vesicles .…”

Icosahedral boron clusters: a perfect tool for the enhancement of polymer features

“…(1,2), meta-(1,7), and para- (1,12)) and metallacarboranes [3,3 0 -M(1,2-C 2 B 9 H 11 ) 2 ] À , M = Co(III) in (1) and M = Fe(III) in (2). Therefore, the nature of the counter-ion used in electropolymerization and the applied experimental conditions play a very important role in the resulting properties of the COP films.…”

Carboranes in the chemist's toolbox

“…Moreover, its power conversion efficiency exceeds that of the ferrocene-ferrocenium (Fc/Fc + ) couple by a factor of 90, and avoids the problem of electron interception by ferrocenium ion, thereby increasing the survival time of the electron in the photoelectrode. 81,82 In a direct application of this work to the fabrication of electronic devices, Teixidor and coworkers have constructed a 3D array of highly conducting polypyrrole microrings doped with Co(1,2-C 2 B 9 H 11 ) 2 − anions via surface patterning and electropolymerization. 78 A later modification, employing silica aerogels coated by atomic-layer-deposited TiO 2 in place of nanoparticles as a DSC platform, has led to greatly increased performance with photocurrent densities more than twice those of nanoparticle-based photoanodes.…”