Reduction of Emeraldine Base Form of Polyaniline by Pillar[5]arene Based on Formation of Poly(pseudorotaxane) Structure

Abstract

We report on the reduction of polyaniline (PANI) by pillar[5]arene based on the formation of the poly(pseudorotaxane) structure. When pillar[5]arene was mixed with emeraldine base (EB) form of PANI, a blue solution color resulting from the EB form of PANI was diluted over time, and became completely colorless after 180 min. The FT-IR spectrum of the mixture of the EB form of PANI and pillar[5]arene displayed a new band at 1646 cm–1, which was assigned the CO stretching band of benzoquinone. These results indicate that both oxidation of the hydroquinone units of pillar[5]arene and reduction of the EB form of PANI were induced by mixing the EB form of PANI and pillar[5]arene. Pillar[5]arene showed a stronger reducing ability than the unit model of hydroquinone. The ROE correlations between the methylene bridge protons of pillar[5]arene and the benzene protons of PANI indicated that the PANI chain was included into the pillar[5]arene cavity. Formation of the poly(pseudorotaxane) structure between PANI and pillar[5]arene was the main reason for the strong reducing ability of the EB form of PANI.

Solid‐Contact Potentiometric Sensor Based on Polyaniline and Unsubstituted Pillar[5]Arene

“…The solubility of quinhydrone is much lower than that of reduced pillar [5]arene and this explains the precipitation of insoluble product of chemical oxidation of pillar [5]arene from reaction media. The consistent stabilization of oxidized and reduced units can also take place by interaction of neighboring pillar [5]arene molecules aggregated on the elec- trode surface as reported elsewhere [21,26]. Analogous redox reaction with chemically polymerized PANI was observed in organic solvent between the emeraldine salt and pillar [5]arene by optical spectroscopy and cyclic voltammetry [21,26].…”

“…Pillararenes show complexation properties toward various cationic species (paraquat [19], Na + and K + ions [20] which can be modified by introduction of various substituents at hydroxyl groups of the macrocycle. Pillar [5]arene can be reversibly oxidized by PANI similarly to hydroquinone [21] and hence it can participate in the PANI electron exchange reactions followed by potential shift.…”

Magnetite/graphene/polyaniline composite for removal of aqueous hexavalent chromium

“…5 The conjugated PANI has three different structures, i.e., leucoemeraldine (LB), emeraldine (EB), and pernigraniline (PB). 6 It has good reduction behaviors for Cr (VI) to Cr (III) with the electron transfer from the LB or EB states to PB state. 7 PANI in powder form is a good candidate for highly efficient Cr (VI) removal due to high adsorption capacity, low cost, and easily bulk production.…”

Reactivity, aromaticity and absorption spectra of pillar[5]arene conformers: A DFT study

“…Moreover, the cylindrical framework of pillar [5]arenes allows a number of guest molecules to accommodate within its cavity. Pillar [5]arenes have found applications as artificial channels, and stabilizers in nanoparticle formation [5][6][7][8][9], polyrotaxanes and pseudorotaxanes [10][11][12][13], supramolecular polymers [14], organic nanotubes [15], chiral sensors and also as data storage in optical devices and other applications [16]. Depending on the position of the -OH group, pillar [5]arenes possess four conformers.…”