Chemical Oxidative Polymerization of Safranines

Abstract

Phenosafranine and safranine have been oxidized with ammonium peroxydisulfate in acidic aqueous solution. The oxidative coupling of both safranines was proved by gel permeation chromatography demonstrating the presence of oligomeric chains of mass-average molar masses 6500 and 4500 g mol-1 for polyphenosafranine and polysafranine, respectively. A theoretical study of the mechanism of safranine and phenosafranine polymerization was based on the MNDO-PM3 semiempirical quantum chemical computations of the heat of formation of dimeric reaction intermediates, taking into account solvation effects. The study of the redox properties of the hydrated safranines and their reactive species shows that nitrenium cations are the main reactive species generated by the oxidation of the parent safranines with a two-electron oxidant, peroxydisulfate, in the initiation phase. The dominant dimers of safranines are formed by N-C coupling reactions between nitrenium cations and the parent safranines. The main coupling reactions of phenosafranine are N-C2 (C8) and N-C4 (C6); N-C4 (C6) is the dominant coupling mode for safranine. The molecular structure of oligosafranines has been studied by FTIR, Raman, and UV-vis spectroscopies. Besides prevalent unoxidized monomeric units, polymerization products of safranines contain also the iminoquinonoid and newly formed fused phenazine units.

Polyaniline: The infrared spectroscopy of conducting polymer nanotubes (IUPAC Technical Report)

“…The spectrum of sample prepared with a higher concentration of ammonium hydroxide, Am 1-B, exhibits peaks at similar positions as Am 0.2-B, except for the 1547 cm -1 peak which is absent (Table 4). The peak at 1547 cm -1 can be attributed to the aromatic ring-stretching vibration in a substituted phenazine unit [50,56]. The characteristic band of the PANI emeraldine base at 1379 cm -1 is not present in the spectra of Am 0.2-B and Am 1-B.…”

“…The opinions of the participants on this band are not unanimous. A medium peak at 1365 cm −1 corresponds to stretching vibrations in phenazine-type rings or to C-N stretching vibrations [50,55,56]. A shoulder at 1337 cm -1 is attributed to C-N bonding [33], with the C atom belonging to the aromatic ring which is not simply para-substituted but probably 1,2,4-trisubstituted.…”

Fabrication of a stable Ti/TiO x H y /Sb−SnO 2 anode for aniline degradation in different electrolytes

“…9, the main characteristic bands of polyaniline at 827 cm À1 , 1141 cm À1 , 1301 cm À1 , 1502 cm À1 , 1577 cm À1 could be seen in the FT-IR spectrum, corresponding to CAH vibration out of benzene plane, CAN stretching of ANHA(C 6 H 4 )ANHA, stretching vibration of CAN bond linked with benzenoid ring, benzenoid structure (C@C) and quinoid (C@C, C@N), respectively [45]. However, two new characteristic bands of solid intermediate products appeared at 1416 cm À1 and 1445 cm À1 , attributing to the ring stretching vibrations in a newly formed phenazine segment [46,47]. Therefore, a reasonable mechanism to form the solid intermediate products was speculate (Fig.…”

Spectroscopy of Nanostructured Conducting Polymers

“…420 nm) is the first main step and afterwards, propagation occurs by addition of monomer in the PBQ chains. However, many doubts remain, and more recently it has been suggested that the formation of phenazine-like rings also occurs in aniline polymerization [35,36], while for polypyrrole and poly(thiophene) the formation of radical species is the main step in the polymerization mechanism.…”