Solid-state EPR Research Articles

CH4 oxidation to oxygenates with N2O over iron-containing Y zeolites: Effect of preparation

Abstract Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH4 to oxygenates have remained challenging topics so far. In this paper, we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene, which was conducted under water-free conditions followed by a series of calcination. Moreover, extra-framework dinuclear Fe2 + complexes are identified as so-called active α-iron sites on zeolites. ICP-OES, N2 adsorption–desorption test, X-ray diffraction, solid-state 27Al NMR, N2O titration, TEM, EPR and 57Fe Mossbauer spectra were carried out to characterize properties of sample structure, acid sites, as well as the supported iron species. Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites. Compared with catalysts synthesized by conventional impregnation, the samples prepared by the facile approach possess abundant dinuclear Fe2 + complexes but no Fe2O3 bulks and show weak acidity. These lead to a higher oxygenate selectivity in CH4 oxidation to oxygenates. Remarkably, the oxygenate (HCHO and CH3OH) selectivity of 6.5% at 375°C can be eventually obtained.

A detailed aging analysis of MPO4:X (M = Y3+, La3+, Lu3+; X = Bi3+, Pr3+, Gd3+) due to the Xe excimer discharge

Phosphate hosts doped with luminescent ions are widely applied for efficient spectral conversion in light emitting devices. However, in Xe discharge lamps a rapid degradation of light output is observed indicating a decrease in the efficiency of conversion of the VUV output of the Xe discharge. This work aims at providing a better understanding of the degradation mechanism. We summarize peculiar findings made within a survey of different inorganic UV emitting phosphors of the MPO4:X (M = Y, La, Lu; X = Bi, Pr, Gd) type regarding their stability under operation in a dielectric barrier Xe excimer discharge lamp. Test lamps containing these phosphors as a particle layer coating onto the inner wall of the lamp vessel suffer from a rapid degradation which was monitored by the loss of UV radiation output during lamp operation. The thus aged materials were recovered and further analysed by optical spectroscopy. It turned out that the aged materials do not only exhibit a new broad absorption in the UV/visible range, which explains the rapid decline of radiation output during lamp operation, but also that all aged materials show photoluminescence in the red upon exposure to UV radiation. It is argued that this luminescence originates from phosphorus in the oxidation state +III (configuration: [Ne]3 s2) which is present as a point defect. These defects are formed when the respective materials are aged in direct contact with the Xe excimer discharge within the lamp discharge vessel. This detailed study of phosphor aging by means of VUV luminescence spectroscopy as well as temperature and time dependent luminescence spectroscopy and solid state EPR spectroscopy points to the existence of phosphorus +III ([Ne]3 s2) which shows characteristic ns2 luminescence which has not been reported before.

Cu-Al2O3-g-C3N4 and Cu-Al2O3-C-dots with dual-reaction centres for simultaneous enhancement of Fenton-like catalytic activity and selective H2O2 conversion to hydroxyl radicals

Cu-Al2O3-g-C3N4 and Cu-Al2O3-C-dots were synthesized for the first time to enhance the catalytic activity and utilization of H2O2. SEM, TEM, XPS, FT-IR, XRD, TPR and solid-state EPR were used to characterize the catalysts. In the Cu-Al2O3-g-C3N4 system, the electron-rich centre of Cu and electron-deficient site of Al were formed due to the higher electronegativity of Cu. Moreover, Cu ions could coordinate with the hydroxyl on the tri-s-triazine ring of g-C3N4 or the graphene conjugated π-domains of C-dots via the CuOC linkage so that the orbital interactions involving electron transport from π → Cu also induced the formation of an electron-rich Cu centre and an electron-deficient π-electron conjugated system, resulting in the strengthening of the dual-reaction centres. This mechanism was validated by Roman, EPR and XPS spectra. In addition, EPR experiments demonstrated that two electron-transfer processes formed OH in the presence of H2O2. The first electron transfer was from the electron-rich Cu centres to H2O2, and the other was from H2O to the electron-deficient site. Thus, more OH were generated and high H2O2 utilization was achieved in the Cu-Al2O3-g-C3N4 and Cu-Al2O3-C-dots suspension. Furthermore, the turnover frequency (TOF) for the Cu-Al2O3-C-dots and Cu-Al2O3-g-C3N4 dispersions were determined and were found to be much higher than those of the classic homogeneous Fenton reaction. Thus, Cu-Al2O3-g-C3N4 and Cu-Al2O3-C-dots showed high activity and stability for the catalytic degradation of organic pollutants under mild conditions.

Strong intermolecular antiferromagnetic verdazyl-verdazyl coupling in the solid state.

Strong magnetic couplings are generally observed intramolecularly in organic diradicals or in systems in which they are promoted by crystal engineering strategies involving, for example, transition metal ligation. We herein present a strong intermolecularly coupling verdazyl radical in the solid state without the use of such design strategies. The crystal structure of an acetylene-substituted verdazyl radical shows a unique antiparallel face-to-face orientation of the neighboring verdazyl molecules along with verdazyl-acetylene interactions giving rise to an alternating antiferromagnetic Heisenberg chain. Single crystal structural data at 80, 100, 173, and 223 K show that one of the π-stacking distances depends on temperature, while heat capacity data indicate the absence of a phase transition. Based on this structural input, broken symmetry DFT calculations predict a change from an alternating linear Heisenberg chain with two comparable coupling constants J1 and J2 at higher temperatures towards dominant pair interactions at lower temperatures. The predicted antiferromagnetic coupling is confirmed experimentally by magnetic susceptibility, solid-state EPR and NMR spectroscopic results.

Identification and Structural Characterization of the N-terminal Amyloid Core of Orb2 isoform A

Orb2 is a functional amyloid that plays a key role in Drosophila long-term memory formation. Orb2 has two isoforms that differ in their N-termini. The N-terminus of the A isoform (Orb2A) that precedes its Q-rich prion-like domain has been shown to be important for Orb2 aggregation and long-term memory. However, besides the fact that it forms fibrillar aggregates, structural information of Orb2 is largely absent. To understand the importance of the N-terminus of Orb2A and its relation to the fibril core, we recorded solid-state NMR and EPR data on fibrils formed by the first 88 residues of Orb2A (Orb2A88). These data show that the N-terminus of Orb2A not only promotes the formation of fibrils, but also forms the fibril core of Orb2A88. This fibril core has an in-register parallel β-sheet structure and does not include the Q-rich, prion-like domain of Orb2. The Q-rich domain is part of the unstructured region, which becomes increasingly dynamic towards the C-terminus.

Supramolecular assemblies in [Cu(L-Arg)2(H2O)]C2O4·6H2O complex – Structural, spectroscopic, magnetic and thermal behavior

The reaction of l-arginine and oxalate ions with copper(II) salts yields a new complex with formula of [Cu(L-Arg)2(H2O)]·C2O4·6H2O (1) (where L-Arg = L-arginine). Single crystals of 1 were synthesized by crystallization from aqueous solution. The complex properties were characterized by X-ray diffraction, spectroscopy (FT-IR, FT-Raman, NIR-Vis-UV and EPR) as well as thermal and magnetic methods. The square pyramidal (SP) geometry around Cu(II) ions in [Cu(L-Arg)2(H2O)]2+ cation complex is formed by two cis-chelated l-arginine zwitterions and a water molecule coordinated in the apex of square pyramid. The trigonality distortion of SP geometry is relatively small, τ = 0.0087. The solid state EPR spectrum showed broad hyperfine splitting with g⊥ = 2.061 at 77 K. The copper centres distanced at 7.558(5) Å are joined in a single zig-zag structure via a chain based on the combination of CuO(5)H(29)⋯O(2)C1O1Cu hydrogen bonds along the b axis (d (O2⋯O5) = 2.812 Å). Taking into account the structural features, the magnetic susceptibility data were best-fitted, giving the exchange parameter J = −0.16 cm−1. Complex 1 is thermally stable up to 66 °C, where it was observed to lose the crystallization water molecules with an 11.7% mass loss (calc. 11.5%).

Structural and magnetic properties of dinuclear Cu(II) complexes featuring triazolyl-naphthalimide ligands

Naphthalimide-based ligands have received significant attention for their ability to act as secondary building units for metal containing network structures. The potentially bridging 1,2,4-triazole containing N-(1,2,4-triazolyl)-1,8-naphthalimide (L1) and N-(1,2,4-triazolyl)-4-dimethylamino-1,8-naphthalimide (L2) were prepared, characterized, and complexed with Cu(II) salts. L1 resulted in crystallographically characterized dinuclear complexes, [Cu2(L1)4(NO3)4] and [Cu2(L1)2(OAc)4] when reacted with Cu(NO3)2 and Cu2(OAc)4, respectively. Packing interactions are dominated by π⋯π and anion⋯π interactions and gave rise to structure extension through weak supramolecular interactions. Solid state EPR and magnetism measurements on [Cu2(L1)4(NO3)4] revealed the expected values for a non-magnetically coupled square-based pyramidal dimer structure, while [Cu2(L1)2(OAc)4] showed strong anti-ferromagnetic coupling (JCu–Cu = −185.6 cm−1).

Axial Mn-CCN Bonds of Cyano Manganese(II) Porphyrin Complexes: Flexible and Weak?

Three five-coordinate high-spin (cyano)manganese(II) complexes, utilized tetraphenylporphyrin (TPP), tetratolylporphyrin (TTP), and tetramesitylporphyrin (TMP) as ligands, are prepared and studied by single-crystal X-ray, FT-IR, UV-vis, and EPR spectroscopies. The crystal structure studies revealed noteworthy structural features including unexpectedly wide tilting angles of the axial Mn-CCN bonds, which is contrasted to the isoelectronic Fe(III)-CCN bonds. Solid-state EPR measurements (90 K) and simulations are applied to obtain the ZFS parameters (D, E, and E/D (λ)), which are compared to Mn(II) porphyrin analogues of hemes to understand the ligand field of the cyanide. The solution EPR studies gave new insights into the chemical equilibrium of four- and five-coordinate species, which has been monitored by UV-vis spectroscopy.

Divalent manganese, cobalt and nickel chloride complexes with neutral N2- and N3-based ligands derived from 2-pyridinecarbaldehyde: Synthesis, structural features and spectroscopic studies

A series of dihalide M(II) mononuclear complexes in a cis configuration, Mn(HL1)2Cl2·CH3OH·H2O (1), Co(HL1)2Cl2·CH3OH·H2O (2), Ni(HL1)2Cl2·2H2O (3) and CoL2Cl2·0.5dmf (4) (HL1 – Schiff base ligand 4-N-(2′-pyridylimine)benzoic acid; L2 – pyridin-2-yl(3-(pyridin-2-yl)imidazo[1,5-a]pyridin-1-yl) methanone, both formed in situ from 2-pyridinecarbaldehyde), have been obtained as single crystals and characterized by elemental analysis, IR and EPR spectroscopy, and single-crystal X-ray diffraction techniques. The neutral M(L1)2Cl2 and CoL2Cl2 molecules in 1–3 and 4, respectively, show no crystallographically imposed symmetry with the metal atoms in a MN4Cl2 distorted octahedral (1–3) and CoN3Cl2 (4) elongated trigonal–bipyramidal geometries. In the crystal lattice molecules of 1–3 are arranged in columns propagating along the c axis; the structure of 4 can be described as layers of CoL2Cl2 and dmf molecules alternating along the a axis. The minimum M⋯M separations in a column (1–3) and inside a layer (4) are above 8Å. The X-band solid-state EPR spectra of 1 at room temperature and 77K exhibit broad fine structure signals at 1600 and 3000G (geff∼4.14 and 2.22, respectively) resulting from ZFS of the spin states for the high-spin d5 metal ion. The solid-state EPR spectra of 2 are temperature dependent showing a wide unresolved line at geff∼2.09 at room temperature and a very broad signal (ΔHpp=2500 G) at geff∼4.21 at 77K. The Ni analogue 3 is EPR-silent. The EPR spectra of 4 at both temperatures show a broad asymmetrical signal centred at g∼2 suggesting the low-spin configuration; the line width is nearly independent of temperature.

Insights into the Reaction Mechanism of Cyclohexane Oxidation Catalysed by Molybdenum Blue Nanorings

Molybdenum blue (MB), is a polyoxometalate with a nanoring structure comprising Mo5+–O–Mo6+ bridges, which is active for the catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone. However, little is known about the mechanistic features responsible of this catalytic activity. In the present work, the Mo5+–O–Mo6+ moieties embedded in the MB nanoring structure were characterized using diffuse reflectance-UV–Visible spectroscopy and solid state EPR spectroscopy. The amount of Mo5+ centres was then varied by thermal treatment of the polyoxometalate in the absence of oxygen, and the resultant effect on the catalytic activity was investigated. It was observed that, an increased amount of Mo5+ centres preserved the conversion of cyclohexane (ca. 6 %) but led to a loss of selectivity to cyclohexanol giving cyclohexanone as the major product, and the simultaneous formation of adipic acid. To rationalise these results the catalysts were studied using EPR spin trapping to investigate the decomposition of cyclohexyl hydroperoxide (CHHP), a key intermediate in the oxidation process of cyclohexane. This analysis showed that CHHP has to be bound to the MB surface in order to explain its catalytic activity and product distribution.

Solid-state EPR strategies for the structural characterization of paramagnetic NO adducts of frustrated Lewis pairs (FLPs).

Anisotropic interactions present in three new nitroxide radicals prepared by N,N addition of NO to various borane-phosphane frustrated Lewis pairs (FLPs) have been characterized by continuous-wave (cw) and pulsed X-band EPR spectroscopies in solid FLP-hydroxylamine matrices at 100 K. Anisotropic g-tensor values and (11)B, (14)N, and (31)P hyperfine coupling tensor components have been extracted from continuous-wave lineshape analyses, electron spin echo envelope modulation (ESEEM), and hyperfine sublevel correlation spectroscopy (HYSCORE) experiments with the help of computer simulation techniques. Suitable fitting constraints are developed on the basis of density functional theory (DFT) calculations. These calculations reveal that different from the situation in standard nitroxide radicals (TEMPO), the g-tensors are non-coincident with any of the nuclear hyperfine interaction tensors. The determination of these interaction parameters turns out to be successful, as the cw- and pulse EPR experiments are highly complementary in informational content. While the continuous-wave lineshape is largely influenced by the anisotropic hyperfine coupling to (14)N and (31)P, the ESEEM and HYSCORE spectra contain important information about the (11)B hyperfine coupling and nuclear electric quadrupolar interaction. The set of cw- and pulsed EPR experiments, with fitting constraints developed by DFT calculations, defines an efficient strategy for the structural analysis of paramagnetic FLP adducts.

Synthesis and characterization of new chiral Cu(ii)-N4 complexes and their application in the asymmetric aza-Henry reaction.

Cu(ii) Schiff base complexes Cu(ii)- and Cu(ii)- based on 2-acetyl pyridine with both (1R,2R)-1,2-diaminocyclohexane and (1S,2S)-1,2-diaminocyclohexane were synthesized in a single step. Subsequent reduction of ligands and with NaBH4 followed by complexation with Cu(OTf)2 resulted in generation of two more additional chiral centers in complexes Cu(ii)- and Cu(ii)-. The ligands and their corresponding complexes were well characterized by several spectral techniques like (1)H-NMR, (13)C-NMR, LC-MS, CD, UV-Vis spectroscopy and microanalysis. The respective Cu(ii) complexes derived from ligands and were investigated using both the solution and solid state EPR spectra. The particular orientation of the reduced complex with Cu(OTf)2 was confirmed by the X-ray crystal structure of the corresponding complex. All the catalytic protocols were applied in the asymmetric aza-Henry reaction to evaluate the catalytic properties of the Cu(ii) complexes in the present study.

Fourier-transform electron spin resonance with bandwidth-compensated chirp pulses

Electron spin echo experiments using chirp pulses at X-band around 9GHz have been performed with a home-built spectrometer based on an arbitrary waveform generator. Primary echoes without phase dispersion were obtained by employing the Böhlen–Bodenhausen scheme with the refocusing pulse being half as long as the coherence-generating pulse. To account for physical bandwidth limitation by the resonator, the instantaneous sweep rate of the chirps was adapted to the spectrometer’s frequency response function, which can be recorded from the sample under study within a few minutes. Such bandwidth-compensated chirp pulses are experimentally shown to achieve an almost uniform excitation bandwidth that exceeds the resonator bandwidth.This uniform excitation allows for computing frequency-domain spectra by Fourier-transformation (FT) of the echo signal. For a nitroxide in dilute solid solution with a spectral width of 200MHz, the FT EPR spectrum agrees remarkably well with a field-swept echo-detected EPR spectrum. The overall spectral perturbation for operation far beyond the resonator bandwidth was characterized by acquiring a 700MHz wide spectral range of a copper (II) EPR spectrum with nearly uniform amplitude with excitation and refocusing pulses of 200 and 100ns, respectively.Furthermore, peculiarities were observed in solid-state FT EPR spectra of disordered systems. To understand these peculiarities two-dimensional data sets were acquired that correlate the FT EPR spectrum to inversion recovery or nuclear modulation. The echo envelope modulation experiments reveal echo decay rates increased by enhanced instantaneous diffusion and passage-specific effects in the nuclear modulations. The latter effect can be suppressed by nuclear modulation averaging. Apparent longitudinal relaxation times for a given subset of orientations are influenced by nuclear modulation effects. Proper extraction of orientation-dependent relaxation times thus requires an experimental setup that minimizes the modulations.

UVA generated free radicals in irinotecan (CPT-11) in the presence of copper ions

Abstract Irinotecan (CPT-11) is an efficient anticancer drug approved for clinical use in the treatment of advanced colorectal cancers. This work is focused on the study of photoinduced processes in irinotecan (CPT-11) both in the presence and absence of Cu(II) ions by means of UV/vis and EPR spectroscopy. Solid-state EPR revealed the solvent dependent coordination between CPT-11 and cupric ions. EPR spin trapping technique, using various spin trapping agents, was applied to monitor the generation of reactive radical species (oxygen- and carbon-centered radicals) in irradiated CPT-11 and CPT-11/CuCl 2 systems under the given experimental conditions. We confirmed that the presence of CPT-11 is necessary for the formation of reactive radicals and the photoinduced processes are influenced by the presence of cupric ions. ROS generated upon irradiation of CPT-11 in the presence/absence of copper ions can be regarded as complementary species to the original inhibitory action of the drug on the DNA topoisomerase I.

Experimental and computational studies of the neutral and reduced states of indeno[1,2-b]fluorene.

This study examines the intrinsic structural and optoelectronic properties of the neutral indeno[1,2-b]fluorene skeleton as well as those of the corresponding anion radical and dianion. We report their characterization by analysis of solid-state structures and EPR, NMR, and absorbance spectra. Additionally, 20 popular density functional theory methods are used to evaluate their performance for predicting NMR chemical shifts, EPR hyperfine coupling constants, and low-energy transitions of the absorbance spectrum to act as a guide for future studies. This information can be used for a better understanding and tuning of the electron-transporting/accepting ability of the indenofluorene core for use in organic photovoltaics and organic field effect transistors.

Weakening of the π*–π* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl2C6H3CNSSN

A series of dichlorophenyl dithiadiazolyls (DCP-DTDA) have been prepared and structurally characterized by X-ray diffraction (1 = 2,3-DCP-DTDA; 2 = 2,4-DCP-DTDA; 3 = 2,5-DCP-DTDA, 4 = 3,4-DCP-DTDA and 5 = 3,5-DCP-DTDA). All the radicals adopt cis-cofacial π*–π* dimers with intra-dimer S⋯S contacts in the range 3.119(8)–3.300(5) A. The propensity for chloro-aromatics to adopt a β-sheet structure assists formation of lamellar structures in 1–5 with intra-stack Cl⋯Cl contacts in the range 3.44(1)–3.82(1) A. Perpendicular to the stacking direction, the packing is dominated by formation of intermolecular S⋯Cl contacts. Variable-temperature magnetic susceptibility measurements on 1–5 in the range 5–300 K reveal the onset of paramagnetism around ca. 200 K. Solid-state EPR studies reveal that this paramagnetism is associated with thermal population of a triplet excited state. A good fit to the Bleaney–Bowers model determined the exchange interactions (2J) between the radicals in the dimers to be in the range −904 to −1529 cm−1. Computational studies of the dimerisation process indicate that at intra-dimer S⋯S distances in excess of 3.2 A the closed-shell singlet becomes destabilized with respect to both the open-shell singlet and triplet state configurations.

Fabrication of two supramolecular self-assemblies of Mn(II)-dicarboxylates with trans-4,4′-azobispyridine: Analysis of H-bonding interactions with Hirshfeld surfaces and DFT calculations

Reactions with an aliphatic dicarboxylate (oxalate) as well as an aromatic dicarboxylate (terepthalate) in combination with an N,N′ donor ligand (trans-4,4′-azobispyridine) results two new coordination polymer of divalent manganese, namely {[Mn(azbpy)(H2O)4]·(bdc)·(H2O)2}n, (1) and {[Mn(ox)(H2O)2]·(azbpy)·(H2O)2}n,(2). Both the coordination polymers have one dimensional structure and extended to two-dimension by means of H-bonding. Interestingly, in solid state structure, the hydrogen bonding interaction recognizes the dicarboxylate (bdc) in case of 1 and N donor ligands (azbpy) in 2. The variation in the use of dicarboxylates, creates here a huge variation in the co-ordination modes of the metal ion as well as in the supramolecular structure within the crystal of 1 and 2. The contribution of various types of non-covalent forces are quantitatively explained in the light of Hrishfield surface analysis, which justifies the role of hydrogen bonding in the recognition of the above organic linkers. A DFT calculation of NBO also gives a quantitative understanding of the formation of the solid state structure by H-bonding. A thermogravimetric analysis, solid state fluorescence spectra and EPR spectroscopic study of the complexes have also performed which also nicely corroborated their crystal structures.

A novel sulfur–nitrogen π-heterocyclic radical anion, (6H-1,2,3-benzodithiazol-6-ylidene)malononitrilidyl, and its homo- and heterospin salts

(6H-1,2,3-Benzodithiazol-6-ylidene)malononitrile (4) was electrochemically and chemically reduced with tetrakis(dimethylamino)ethylene (TDAE) and CrTol2 into the title radical anion (5). The electrochemically generated 5 and its salts [TDAE]2+[5]2 (7) and [CrTol2]+ [5] (8) were characterized by solution EPR in combination with UV–Vis spectroscopy. Salts 7 and 8 were isolated and characterized by elemental analysis and solid-state EPR, and 8 by magnetic measurements in the temperature range 2–300K. The value of the effective magnetic moment of the salt 8 at 300K, μeff=1.64μB, indicates π-dimerization of 5 in the solid state. For the molar magnetic susceptibility χ of 8, the temperature dependences of χT and 1/χ in the range 2–300K can be approximated by the Curie–Weiss law with the Curie–Weiss constant C and temperature Tc equal to 0.33±0.01cm3Kmol−1 and −1.0±0.1K, respectively. In the mean-field approximation, the effective value of the exchange interaction of [CrTol2]+ with its neighboring cations can be estimated as zJ=−1.4сm−1. All the experimental results were supported by DFT calculations.

Immobilization of Ru(III) complex on silica: a heterogenized catalyst for selective oxidation of alcohols in water at room temperature

We have developed a heterogenized catalyst (‘SiO2’–NH2–RuIII) by the immobilization of [Ru(acac)2(CH3CN)2]PF6 on SiO2. The catalyst was characterized by SEM, solid state NMR, EPR, FT-IR, ICP, and BET surface area analyses. ‘SiO2’–NH2–RuIII catalyzed the selective oxidation of alcohols with periodic acid in water at room temperature. This protocol was applicable to the controlled oxidation of structurally diverse primary and secondary alcohols. The catalyst could be quantitatively recovered and reused up to six cycles without significant loss of catalytic activity.

Nanostructures obtained in the oxidative polymerization of aniline: Effects of polarons

Effects of polarons on the single (NH4OH) and double (NH4OH + LiOH) dedoped nanostructured products obtained in the oxidative polymerization of aniline are investigated. These effects are probed by 15N and 13C solid-state NMR, FTIR, Raman and EPR spectroscopy. The morphologies were imaged using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The micrographs confirmed the presence of mixed morphologies which include granular and nanotubular products. Single dedoping with NH4OH (SD) was not sufficient to completely remove positive charges. Subsequent dedoping with LiOH (DD) significantly removed positive charges. NMR experiments confirmed that the imine part of the structure has been more exposed to the effects of polarons. EPR data showed that the spin concentration in the DD samples was more than an order of magnitude lower that of the SD sample. The FTIR and Raman spectra exhibit characteristic bands for polyaniline and oligoanilines.