Anilinium Cations Research Articles

Network films of conducting polymer-linked polyoxometalate-modified gold nanoparticles: Preparation and electrochemical characterization

The ability of Keggin-type phosphododecamolybdate (PMo 12O 40 3−, PMo 12) to undergo chemisorption on solid surfaces (including gold) is explored here to convert (by ligand place-exchange and phase transfer to aqueous solution) the alkanothiolate-modified Au nanoparticles of controlled size (prepared in toluene) into a stable colloidal solution of PMo 12-protected gold nanoparticles, PMo 12–AuNPs, the sizes of which are ca. 4–5 nm as determined by transmission electron microscopy. By dip-coating, PMo 12–AuNPs were assembled on carbon electrode substrates. The step-by-step assembly, by which alternate exposures to the solutions of PMo 12–AuNPs and either anilinium cations or pyrrole monomers, was utilized to grow in controlled manner hybrid network films in which the negatively charged PMo 12–AuNP deposits were linked, or electrostatically attracted, by ultra-thin, positively charged conducting polymer (polyaniline or polypyrrole) structures. The three-dimensionally distributed PMo 12–AuNPs immobilized within the polypyrrole-based composite film exhibited some electrocatalytic reactivity towards reduction of hydrogen peroxide.

Varying electronegativity: Effect of the nature and strength of H-bonding in anilide/aniline/anilinium complexes on the electronegativity of [formula omitted] groups

Application of the Domenicano et al. [A.R. Campanelli, A. Domenicano, F. Ramondo, I. Hargittai, J. Phys. Chem. A, 108 (2004) 4940.] method of estimating group electronegativity from angular geometry of the ring in monosubstituted benzene derivatives allowed us to find out how electronegativity of the NH - / NH 2 / NH 3 + groups in H-bonded complexes of the anilide anion, aniline and the anilinium cation depends on the nature and strength of the H-bond. For complexes in which the NH 2 group is only a proton donating moiety the estimated electronegativity of the group increases with an increase of the N…base interatomic distance. An opposite relationship is found for cases where nitrogen is a proton acceptor. The observed relationship between the electronegativity, χ, and the C–N bond lengths as well as the intermolecular N…B (base) or HB (H–base) distances are monotonic when calculated for isolated systems using molecular modeling, for crystal structures (the retrieved data from CSD [F.H. Allen, Acta Crystallogr., Sec. B: Struct. Sci., 58 (2002) 380.]), however, are blurred by numerous crystal packing forces. The modeling was carried out using B3LYP/6-311 + G ∗∗ level of theory.

Long-Distance Structural Consequences of H-Bonding. How H-Bonding Affects Aromaticity of the Ring in Variously Substituted Aniline/Anilinium/Anilide Complexes with Bases and Acids

The aromaticity of the ring in variously substituted aniline/anilinium/anilide derivatives in their H-bonded complexes with various Broensted acids and bases was a subject of an analysis based on 332 experimental geometries retrieved from the Cambridge Structural Database and geometries optimized at the B3LYP/6-311+G** and MP2/aug-cc-pVDZ levels of theory. Ab initio modeling was applied to the para-substituted aniline, anilinium cation, and anilide anion derivatives (X = NO, NO2, CN, CHO, H, CH3, OCH3, and OH) and their H-bonded complexes (only for X = NO, NO2, CHO, H, and OH) with B (B = F- and CN-) or HB (HB = HF and HCN). In both cases, the harmonic oscillator model of aromaticity index (HOMA) was used, whereas for computational geometries, additionally, the magnetism-based indices NICS, NICS(1), and NICS(1)zz were also applied (NICS = nucleus-independent chemical shift). There is an equivalent prediction of aromaticity by NICSs and HOMA and approximate monotonic dependences of HOMA and NICS on the C-N bond length. The strongest changes in aromaticity estimated by HOMA and NICSs were found for aniline derivatives with NH2...B and anilide derivatives without and with NH-...HB interactions. The changes observed for two other kinds of interactions, NH2...HB and NH3+...base (for anilinium cations), are much smaller. For all four kinds of interactions, the relationships between ipso-bond angle, mean ipso-ortho bond length, and C-N bond length follow the Bent-Walsh rule.

New Aspects of the Low-Concentrated Aniline Polymerization in the Solution and in SiC Nanocrystals Dispersion

Results of the simultaneous in-situ UV-vis and open-circuit potential (OCP) monitoring of the low-concentrated aniline (An) polymerization in the presence of camphorsulfonic acid (CSA) suggested that during the induction period (IP) step a transition state formed, which probably included anilinium cation and the oxidant anion, antecedent to a propagation step. No aniline oligomers were registered at this stage but they appeared at the beginning of the propagation step under the investigation conditions. The moments of formation of insoluble pernigraniline phase and appearance of emeraldine units in the growing pernigraniline chains were ascertained by the comparison of kinetic and OCP profiles of the polymerization process both in the solution and in SiC dispersion water mediums. It is deduced that pernigraniline reduction by aniline molecules begins earlier than it is generally accepted (i.e., earlier than OCP maximum is reached) and probably in parallel to a continuing appearance of pernigraniline units even in the same chains that undergo the reduction. It was found that an addition of the SiC dispersion phase into the polymerization mixture accelerates differently all stages of the aniline polymerization. Finally, this polymerization process leads to the formation of polyaniline (PANI)-CSA shell with thickness in the range from 0.5 nm to a few nm at the SiC nanocrystals surface.

The genesis of polyaniline nanotubes

Aniline has been oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. Protons are produced in the course of oxidation and the pH decreases as the reaction proceeds. The oxidation had two subsequent phases: (1) the oxidation of the neutral aniline molecules and the initially produced low-molecular weight aniline oligomers at low acidity, followed by (2) the oxidation of the anilinium cation after the acidity became higher. The two phases of oxidation gave different products, aniline oligomers with mixed ortho- and para-coupling of aniline molecules, and polyaniline nanotubes, respectively. The aniline oligomers are produced at first at low acidity, pH > 4, some of them as rod-like crystals. The molecular weight of the oligomers has been assessed by gel-permeation chromatography to be of several thousands. The 2–3 wt.% content of sulfur in deprotonated samples suggests that the oxidation products are partly sulfonated. The oxidation of ortho-coupled anilines combined with intramolecular cyclization produces phenazine units or their blocks, as indicated by FTIR spectra. A high-molecular weight polyaniline is produced at pH < 2. The protonation of the intermediate pernigraniline form of polyaniline is a prerequisite for the polymerization. The nano-sized oligomer crystallites serve as starting templates for the nucleation of PANI nanotubes. Further growth of nanotubes proceeds by the self-organization of the phenazine units or their blocks located at the ends of the PANI chains. Polyaniline nanotubes have a typical outer diameter of 100–200 nm, with a wall thickness of 50–100 nm, an inner diameter of 0–100 nm, and a length extending to several micrometres.

Chemical Oxidative Polymerization of β-Cyclodextrin/Aniline Inclusion Complex

A β-cyclodextrin (β-CD)/aniline inclusion complex has been synthesized in aqueous solution and characterized by FT-IR and 1H-NMR spectroscopy, chemical analysis and thermogravimetric method. By elemental analysis and 1H-NMR spectroscopy a complex with stoichiometry 1:1.95 and 1:1.8 (β-CD/aniline) respectively, is found. The complexed aniline was polymerized by chemical oxidative polymerization using ammonium peroxydisulfate in water (pH = 7) and 1M HCl aqueous solution. In both cases, after an induction period, insoluble polyanilines (PANIs) are obtained, however, in water at pH = 7, a polypseudorotaxane architecture containing a β-CD molecule to ~14 aniline units has resulted. In acidic conditions, anilinium cation is highly hydrophilic and inclusion complex has a strong tendency to dissociate to free molecules and emeraldine salt of PANI, free of host molecules is synthesized.

2-(Methoxycarbonyl)anilinium chloride monohydrate

The asymmetric unit of the title compound, C8H10NO2+·Cl−·H2O, contains two crystallographically independent 2-(methoxy­carbon­yl)anilinium cations related by a pseudo-inversion centre, two chloride ions and two water mol­ecules. A three-dimensional network structure is formed via N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, and π–π stacking inter­actions.

X-ray diffraction studies of intercalation compounds prepared from aniline salts and montmorillonite by a mechanochemical processing

Inorganic–organic intercalation compounds comprised of montmorillonite (MMT) and aniline salts with different counter anions were prepared by a mechanochemical processing. The intercalation process and the formed structure of intercalation compounds were investigated via X-ray diffraction analysis. The amounts of intercalated species were very likely dependent on the types of counter anions and increased with decreasing the size of counter anions during the mechanochemical processing. Very interestingly, much larger interlayer expansions of 1.51 nm was observed for aniline hydrofluoride AnF– and aniline hydrochloride AnCl–MMT systems in higher intercalates loading levels, suggesting that neutral guest molecules also introduce within the interlayer regions together with anilinium cations by van der Waals interactions. Judging from the larger interlayer expansions and the size of guest molecules, intercalated species are expected to prefer a tri-molecular layer arrangement with their aromatic rings perpendicular to the silicate sheets. In contrast, for aniline hydrobromide AnBr–MMT, the interlayer expansion was ca. 0.52 nm, which reveals that only anilinium cations are introduced by ion exchange and they probably adopt a vertical orientation in the interlayers. It is inferred that aniline hydroiodide AnI–MMT compounds have a heterogeneous structure containing both anilinium and sodium cations in the interlayers. Different intercalation behaviors during the mechanochemical processing strongly suggest the smaller the size of counter anions, the more guest molecules can be intercalated into the confined clay interlayers in highly ordered arrangements.

Network electrocatalytic films of conducting polymer-linked polyoxometallate-stabilized platinum nanoparticles

To fabricate electrocatalytic network films containing Pt nanoparticles, the ability of a Keggin-type polyoxometallate, phosphododecatungstate (PW 12O 40 3−), to form stable anionic monolayers on solid surfaces is explored. Three-dimensional assemblies on electrode (glassy carbon or platinum) surfaces are grown using the layer-by-layer method involving repeated alternate treatments in the solution of PW 12O 40 3− (or in the colloidal suspension of polyoxometallate-protected Pt-nanoparticles) and in the solution of monomer (e.g., anilinium) cations. In the resulting structured (organic–inorganic) films, the layers of negatively charged polyoxometallate, or polyoxometallate-protected (stabilized) Pt-nanoparticles, interact electrostatically with the ultra-thin layers of such a positively charged conducting polymer as polyaniline. Consequently, physicochemical properties of organic conducting polymers, and reactivities of inorganic polyoxometallate and/or noble metal particles can be combined. The modification of Pt nanoparticles by adsorbing monolayers of phosphododecatungstate tends to activate them towards efficient electrocatalytic reduction of oxygen in acid medium.

Polyaniline/TiO 2 microspheres prepared by a template-free method

Polyaniline/TiO 2 microspheres with 2.5–3.6 μm in average diameter were synthesized by a template-free method in the presence of salicylic acid (SA) as the dopant. It was found that the morphology, conductivity and hydrophilicity of the PANI-SA/TiO 2 microspheres were affected by the content of TiO 2 nanoparticles. The micelles composed of SA anions and anilinium cations containing TiO 2 were proposed to interpret the formation mechanism of the self-assembled composite microspheres.

X-ray diffraction study of acid anilinium dodecatungstenphosphate

Acid anilinium dodecatungstenphosphate of composition (C6H5NH3)2H[PW12O40] ⋅ 2H2O is synthesized and characterized by X-ray diffraction analysis, IR spectroscopy, and thermogravimetry. The crystals are monoclinic: space group P21/m, a = 9.940(2) A, b = 15.412(3) A, c = 16.201(3) A, β = 100.42(3)°, Z = 2, ρcalcd = 4.221 g/cm3. The structure contains heteropolyanions [PW12O40]3−, cations [C6H5NH3]+ and H+, and molecules of water of crystallization. The heteropolyanions and anilinium cations in crystal are linked by the electrostatic interaction and hydrogen bonds.

Structural and vibrational studies of anilinium nitrate

The crystals of anilinium nitrate, C6H8N+·NO3−, were obtained by slow evaporation of an aqueous solution. The crystals belong to the Pbca (no. 61) space group of orthorhombic system, Z=8, a=10.158(2), b=9.277(2), c=16.177(3)Å. Positively charged anilinium cations and NO3− anions are present in the structure. Powder FT IR and FT Raman spectra for normal and deuterated samples are discussed with respect to the crystal structure. DSC measurements do not indicate clearly on the occurrence of phase transition in the temperature region 113–293K.

Chiral polyaniline nanotubes synthesized via a self-assembly process

Electrical and optical active polyaniline (PANI) nanotubes doped with (1R)-(−)-10-camphorsulfonic acid (L-CSA) and (1S)-(+)-10-camphorsulfonic acid (D-CSA) as a chiral dopant, which have 80 to 200 nm in outer diameter and 20 to 40 nm in inner diameter, were synthesized via a self-assembly process. It was found that the formation yield and the size of the nanotubes is affected by the molar ratio of CSA to aniline; however, the influence of the configuration of CSA on their formation yield and morphology and size could be neglected. The nanotubes not only show electrical properties (∼10 −2 S/cm) but also exhibit optically activity that Cotton effects corresponding to a helical screw of the polymer chains were observed by the circular dichroism (CD) spectra. The micelles composed of anilinium cations and CSA anions were proposed as templates in the formation of the chiral nanotubes.

Network Films Composed of Conducting Polymer-Linked and Polyoxometalate-Stabilized Platinum Nanoparticles

The ability of Keggin-type phosphododecamolybdates (PMo12O403-) to undergo chemisorption and to form anionic monolayers on platinum surfaces is explored here to produce stable colloidal solutions of polyoxometalate-protected platinum nanoparticles (size, 5−10 nm, as determined by transmission electron microscopy and scanning tunneling microscopy). By dip-coating in the above solution, the particles can readily be assembled on carbon electrode substrates. The layer-by-layer method, which involves alternate exposures to the solutions of PMo12O403--stabilized Pt nanoparticles and anilinium cations, has been utilized to grow in a controlled manner hybrid network films in which the negatively charged layers of polyoxometalate-protected Pt nanoparticles are linked, or electrostatically attracted, by ultrathin positively charged polyaniline layers. The phosphomolybdate-decorated Pt nanoparticles (immobilized within ultrathin polyaniline film) are attractive for electrocatalysis: they show promising reactivity t...

Polyoxometallates as inorganic templates for electrocatalytic network films of ultra-thin conducting polymers and platinum nanoparticles

We develop a concept of fabrication of the multilayer network films on electrodes by exploring the ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo 12O 40 3−), to form stable anionic monolayers (templates) on carbon and metals including platinum. By repeated alternate treatments in the solution of PMo 12O 40 3− (or in the colloidal suspension of polyoxometallate-protected Pt-nanoparticles) and in the solution of monomer (e.g. anilinium) cations, the amount of the material can be increased systematically (layer-by-layer) to form stable three-dimensional assemblies on electrode (e.g. glassy carbon) surfaces. In the resulting hybrid (organic–inorganic) films, the layers of negatively charged polyoxometallate, or polyoxometallate-protected (stabilized) Pt-nanoparticles, are linked or electrostatically attracted by ultra-thin layers of such positively charged conducting polymers as polyaniline (PANI), polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene), PEDOT. Consequently, the attractive physicochemical properties of polymers and reactivity of polyoxometallate or noble metal particles are combined. The films are functionalized and show electrocatalytic properties towards reduction of nitrite, bromate, hydrogen peroxide or oxygen. They are of importance to the chemical and biochemical sensing as well as to the biochemical and medical applications.

Synthesis of polyaniline–montmorillonite nanocomposites by the mechanochemical intercalation method

Nanocomposites consisting of conducting polyaniline (PANI) and montmorillonite (MMT) were synthesized by the mechanochemical intercalation method. The mixtures of sodium MMT and anilinium chloride were mechanochemically ground in a mortar. X-ray diffraction (XRD) analysis confirmed that anilinium cations, which are the monomer of PANI, were intercalated into MMT by a cation-exchange reaction between the sodium cations of MMT and the anilinium cations of anilinium chloride. The basal spacing of the anilinium–MMT intercalation compound significantly expanded from 0.96 to 2.47 nm by adding an excess amount of anilinium chloride. After polymerization by the mechanochemical grinding with ammonium peroxodisulfate in a mortar, a decrease in the basal spacing to 1.33 nm was observed, indicating that PANI was synthesized between the interlayer spaces of MMT. It was further characterized by Fourier transform infrared (FT-IR) spectroscopy. The result of thermogravimetric analysis showed the improved thermal stability of PANI due to modification of the incorporated MMT.

Anilinium monohydrogen DL-malate.

Crystals of the title salt, [(C(6)H(5)NH(3))](+).[(HOOC(CH(2))CH(OH)COO)](-) or C(6)H(8)N(+).C(4)H(5)O(5)(-), are built up from protonated anilinium residues and monodissociated DL-malate ions. The NH(3)(+) group of the anilinium cation is ordered at room temperature. Rotation of the NH(3)(+) group along the C(aromatic)-Nsp(3) bond (often observed at room temperature in other anilinium salts) is prevented by N-H.O hydrogen bonds between the NH(3)(+) group and the malate anions. The anions are connected by four O-H.O hydrogen bonds into two-dimensional sheets parallel to the (001) plane. The charged moieties, i.e. the anilinium cations and the sheets of hydrogen-bonded malate anions, form two-dimensional layers in which the phenyl rings of the anilinium residues lie perpendicular to the malate-ion sheets. The conformation of the monodissociated malate ion in the crystal is compared with that obtained from ab initio molecular-orbital calculations.

Polyaniline/TiO2 Composite Nanotubes

Polyaniline (PANI) composite nanotubes (90−130 nm in diameter) containing titanium dioxide (TiO2) nanoparticles (about 10 nm in diameter) were synthesized through a self-assembly process in the presence of β-naphthalenesulfonic acid (β-NSA) as the dopant. It was found that the morphology, size, conductivity, and hydrophobicity of the PANI−β-NSA/TiO2 composite nanotubes were affected by the content of TiO2 nanoparticles in the nanotubes. The micelles composed of β-NSA anions and anilinium cations containing TiO2 were proposed to interpret the formation mechanism of the self-assembled composite nanotubes. The Raman spectra and X-ray diffraction characterizations show that the main chain of the composite nanotubes is identical to that of the doped PANI, and indicate that there is no chemical interaction between PANI and TiO2.

Nanostructures of Polyaniline Doped with Inorganic Acids

With an average diameter of 150−340 nm and a conductivity of 10-1−100 S/cm, nanostructures (e.g., nanotubes or nanorods) of polyaniline (PANI) were synthesized by a self-assembly method in the presence of inorganic acids (e.g., HCl, H2SO4, HBF4, and H3PO4) as dopants. It was found that the morphology, size, and electrical properties of the resulting nanostructures depended on the dopant structures and the reaction conditions. In particular, all these PANI nanostuctures showed hydrophilic features, and the contact angles with water were measured to be about 27−40° depending on the dopant. The FTIR spectrum, UV−vis absorption spectrum, XPS, and X-ray diffraction were used to characterize the molecular structures of the nanostructures. It was found that their main chain structure and electric structure were identical to those of the emeraldine salt form of PANI. The micelles formed by anilinium cations act as the template like in the formation of PANI nanostructures.

Formation and Decomposition of N,N,N-Trimethylanilinium Cations on Zeolite H−Y Investigated by in Situ Stopped-Flow MAS NMR Spectroscopy

Methylation of aniline by methanol on zeolite H-Y has been investigated by in situ (13)C MAS NMR spectroscopy under flow conditions. The in situ (13)C continuous-flow (CF) MAS NMR experiments were performed at reaction temperatures between 473 and 523 K, molar methanol-to-aniline ratios of 1:1 to 4:1, and modified residence times of (13)CH(3)OH between 20 and 100 (g x h)/mol. The methylation reaction was shown to start at 473 K. N,N,N-Trimethylanilinium cations causing a (13)C NMR signal at 58 ppm constitute the major product on the catalyst surface. Small amounts of protonated N-methylaniline ([PhNH(2)CH(3)](+)) and N,N-dimethylaniline ([PhNH(CH(3))(2)](+)) were also observed at ca. 39 and 48 ppm, respectively. After increase of the temperature to 523 K, the contents of N,N-dimethylanilinium cations and ring-alkylated reaction products strongly increased, accompanied by a decrease of the amount of N,N,N-trimethylanilinium cations. With application of the in situ stopped-flow (SF) MAS NMR technique, the decomposition of N,N,N-trimethylanilinium cations on zeolite H-Y to N,N-dimethylanilinium and N-methylanilinium cations was investigated to gain a deeper insight into the reaction mechanism. The results obtained allow the proposal of a mechanism consisting of three steps: (i) the conversion of methanol to surface methoxy groups and dimethyl ether (DME); (ii) the alkylation of aniline with methanol, methoxy groups, or DME leading to an equilibrium mixture of N,N,N-trimethylanilinium, N,N-dimethylanilinium, and N-methylanilinium cations attached to the zeolite surface; (iii) the deprotonation of N,N-dimethylanilinium and N-methylanilinium cations causing the formation of N,N-dimethylaniline (NNDMA) and N-methylaniline (NMA) in the gas phase, respectively. The chemical equilibrium between the anilinium cations carrying different numbers of methyl groups is suggested to play a key role for the products distribution in the gas phase.