Polyaniline and its derivatives doped with Lewis acids (synthesis and spectroscopic properites)

The presented research is devoted to the studies of the doping of polyaniline and its ring substituted derivatives (polyanisidine, poly(2-ethylaniline)) with AlCl3 and FeCl3 as well as with their derivatives containing mixed chloride - acetylacetonate ligands (AlCl2(acac) and (FeCl(acac)2). AlCl3 and FeCl3 doped polymers are conductive and show the electronic type conductivity of the order 10-3 S/cm. Complementary spectroscopic studies involving UV-Vis-NIR, IR, EPR, 27Al NMR (in the case of AlCl3 doping) and 57Fe Mössbauer effect (in the case of FeCl3 doping), combined with elemental analysis, enabled us to elucidate the doping reaction mechanism, which in both cases is the same. The doping involves, in the first step, the self-dissociation of the dopant molecule. The cationic product of this self-dissociation is the complexed on imine nitrogen sites of the polymer chain, whereas the anionic part is incorporated into the polymer matrix to neutralise the positive charge imposed on the polymer chain. The coordination sphere of the cationic complex is completed by solvation with a nitromethane molecule. Charge rearrangement accompanying the doping process produces mobile radical cations on the polymer chain, which assure electronic conductivity of the doped polymer. This mechanism clearly explains the presence of charge carriers and the radical cation structure of the doped polymer chain detected by EPR and UV-Vis-NIR spectroscopies. FeCl3 doped polyaniline shows poor mechanical properties, which can however, be improved by post-treatment with hexafluoroacetylacetone (HFAA). This treatment results in the transformation of FeCl3 (Lewis acid) doped polyaniline into HFeCl4 (Brönsted acid) doped polymer, simultaneously plasticized with HFAA. Doping with mixed ligands (AlCl2(acac) and (FeCl(acac)2.), although being inactive with respect to polyaniline doping, readily dope polyanisidine and poly(2-ethylaniline). The chains of doped polymers adopt the radical cation structure as evidenced by UV-Vis-NIR spectroscopy, however the doping mechanism is more complex than in the case of reaction with AlCl3 or FeCl3. The doping with AlCl2(acac) results in the AlCl3 doped polymer with Al(acac)3 incorporated to the polymer matrix as a side reaction product. Doping with FeCl(acac)2 produces more than expected non-equivalent iron sites of the chemical constitution not easily identifiable by Mössbauer spectroscopy.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Ferromagnetic spins interaction in tetraaza- and hexaazacyclophanes

International audienc

Raman Changes Induced by Electrochemical Oxidation of Poly(triarylamine)s: Toward a Relationship between Molecular Structure Modifications and Charge Generation

International audienc

EPR Spectra of Multispin Systems. Application to Poly-m-p-Aniline

In this communication we present NiceMagnetic, software for simulations and analysis of EPR spectrum and SQUID measurements. Systems of arbitrary number N of spin-only magnetic moments (S ≤ 0 and L = 0) were considered within the lines of the Heisenberg and Zeeman Hamiltonians. Effective algorithms used for the computations are discussed. This includes modified secant method adapted to calculate resonance fields with demanded precision. Finally, application of NiceMagnetic to experimental SQUID magnetization and EPR spectra of poly-m-p-aniline, one of recently synthesized high spin polymers containing unpaired electrons will be presented. As a result, exchange integral between electron and nitrogen nuclei spins (ligand hyperfine interaction) J = 6.3 × 10$\text{}^{-4}$ cm$\text{}^{-1}$ was estimated

EPR Spectra of Multispin Systems. Application to Poly-m-p-Aniline

In this communication we present NiceMagnetic, software for simulations and analysis of EPR spectrum and SQUID measurements. Systems of arbitrary number N of spin-only magnetic moments (S ≤ 0 and L = 0) were considered within the lines of the Heisenberg and Zeeman Hamiltonians. Effective algorithms used for the computations are discussed. This includes modified secant method adapted to calculate resonance fields with demanded precision. Finally, application of NiceMagnetic to experimental SQUID magnetization and EPR spectra of poly-m-p-aniline, one of recently synthesized high spin polymers containing unpaired electrons will be presented. As a result, exchange integral between electron and nitrogen nuclei spins (ligand hyperfine interaction) J = 6.3 × 10$\text{}^{-4}$ cm$\text{}^{-1}$ was estimated

Formation of High-Spin States (S=3/2 and 2) in Linear Oligo- and Polyarylamines

International audienceThis article describes the study of a linear trimer and three polyarylamines PB1-3 containing a 3,4'-biphenyl ferromagnetic coupler. The synthesis of the model compound (trimer) and the polymers has been presented. The formation of radical cations was studied using electrochemical and optical (UV-vis) methods. The chemical oxidation of these compounds leads to the creation of high-spin states, evidenced by pulsed EPR nutation spectroscopy. A quartet spin state is observed for the trimer model compound, and its J exchange coupling constant has been measured experimentally (J/k = 11.8 K) and compared quantitatively to DFT calculations. Most importantly, quartet and quintet spin states have been formed for PB3 and PB2, respectively. These last two doped polymers thus exhibit the highest spin states observed to date for linear polyarylamine compounds