Non-acidic Medium Research Articles

A comprehensive overview of carbazole-EDOT based electrochromic copolymers: A new candidate for carbazole-EDOT based electrochromic copolymer

In recent years, there has been an increase in the demand for the synthesis of carbazole-EDOT based electrochromic copolymers since this combination of structures facilitates the obtaining of a free standing film on the working electrode and improves the electrochromic properties of the polycarbazole (PC) polymer. In this study, carbazole-EDOT based copolymers with electrochromic properties in the literature were classified into three groups and the effect of changing the carbazole/EDOT order on the polymer chain on the electrochromic properties of the obtained copolymer was tried to be revealed. Moreover, as an example, a new candidate for carbazole-EDOT based electrochromic random copolymer was introduced. Carbazole and EDOT monomers were copolymerized electrochemically in nonacidic medium for a clear and basic comparison. The electrochemical and spectroelectrochemical studies show that the corresponding copolymer, poly(C-co-EDOT), contains freestanding property on working electrode and shows multielectrochromic property. The copolymer gave a λmax value at about 545 nm with a band gap of 1.74 eV. As expected, EDOT monomer inserting to the polycarbazole chain improves electrochemical and optical properties of homopolymer PC. The electrochromic performance of new copolymer was also compared with its homopolymers components (polymer of carbazole (C) and EDOT) and carbazole-EDOT based electrochromic random copolymers in literature. The experiments showed that poly(C-co-EDOT) was an electroactive material with higher coloration efficiency (CE) (258 cm2/C at 900 nm) than that of PC and carbazole-EDOT based random copolymers in literature. DFT theoretical and experimental calculations were also achieved in order to find HOMO and LUMO energy levels besides band gap and compared with each other. No such a theoretical calculation related electrochromic PC polymer and that kind of random electrochromic copolymer has ever been encountered in the studies carried out so far. Since this research is a baseline study for the valuable design of carbazole-EDOT based electrochromic copolymer, it is thought to shed light on the scientists who will work on this subject in the future.

Electrochemical Synthesis of Polycarbazole Film in Nonacidic Medium and its Electrochromic Properties

This study is about the electrochemical polymerization of the monomer of carbazole, whose anodic polymerization is very common in the literature. When the studies in the literature were examined, it was seen that the electrochromic properties of carbazole were not examined. For this purpose, electrochemical and optical properties were investigated in detail by polymerizing carbazole on both glassy carbon and ITO glass electrodes in 0.1 M TABPF6/ DCM medium using the cyclic voltammetry method. The polymer film synthesized by electroanalytical methods showed reversible electrochemical oxidation process properties as well as electrochromic properties. The polymer film synthesized by electroanalytical methods showed reversible electrochemical oxidation process properties as well as electrochromic properties. Considering that this study will form a basis for other studies, it is thought that the evaluation of carbazole monomer in terms of its electrochromic properties will provide a great deal to the literature.

Excellent compound inhibitor of carboxymethyl chitosan/magnetic reduced graphene oxide for carbon steel in neutral chloride solution

As an efficient corrosion inhibitor in acidic medium, carboxymethyl chitosan (CMC) has a limited application in non-acidic medium, due to large consumption and high cost. In the study, magnetic reduced graphene oxide (MRGO) is first introduced into CMC inhibitors to enhance the corrosion inhibition. By optimizing, the best corrosion inhibition efficiency of compound inhibitor is attained as high as 91.78% for carbon steel Q235 in 3.5 wt% NaCl solution, with the remarkably decreased amount of CMC from 800 mg L−1 to 40 mg L−1. Our work lays a good foundation for expanding the potential application of CMC and MRGO as non-acidic medium corrosion inhibitor.

Optical and Structural Characteristics of PANI capped PbS Nanoparticles

The modern research communities are now-a-days immensely attracted towards the semi-conductor nanoparticles due to their budding application in both traditional optical devices and new generation of nano-electronic and nano-optoelectronic devices because of their unexpected chemical and physical properties. In this present work, Lead Sulphide (PbS) nanoparticles with diameter in the range of 26–58 nm were synthesized by varying concentration of the conducting matrix Poly-aniline (PANI), using a wet Chemical technique in a non-acidic medium. The precursors used here are Lead Nitrate (Pb(NO3)2) and Sodium Sulphide (Na2S). Polyaniline (PANI) has been used as a conductive capping agent. PbS is synthesized by varying the concentration of conducting matrix PANI while keeping the reaction time constant (i.e 3 hrs). The PANI concentration has been changed from 0.5 gm to 2.0 gm in 5 different samples. Finally the synthesized samples are characterized by using various characterization techniques such as UV–Vis Spectroscopy (UV), Photoluminescence Spectroscopy (PL), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-rayAnalysis (EDAX) and Transmission Electron Microscopy (TEM).

Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N-Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole

Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO2 layer on the surface of the catalytic metal in the fresh catalyst.

Ceric ammonium nitrate and manganese(III) acetate mediated radical oxidation and addition reactions of anthracene and 9-substituted anthracenes

Radical oxidation and addition reactions of anthracene (1), 9-methylanthracene (2) and 9-phenylanthracene (3) were investigated with dimethyl malonate (4) in the presence of ceric ammonium nitrate (CAN) and manganese(III) acetate (Mn(OAc)3). Although mostly anthraquinone derivatives and bianthrone were obtained with CAN, substituted 9,10-dihydroanthracene and 9,10-substituted anthracene derivatives were obtained with Mn(OAc)3. Dimethylmalonyl addition products (5a, 33 % and 5b, 42 %) were obtained in higher yield than quinones (5d, 8 % and 5e, 3 %) using Mn(OAc)3 as oxidant. 9a (96 %) and 9b (84 %) were synthesized in high yield and substitution products (7a, 44 % and 8b, 56 %) were obtained in higher yields than quinones (5d and 5e) using CAN as oxidant. The reactions were carried out in non-acidic medium (dichloromethane and methanol). Based on the structures of the isolated products a mechanism for these transformations was proposed.

Synthesis of a nitro complex of RuIII(salen): Unexpected aromatic ring nitration by a nitrite salt

Reaction of silver nitrite with Ru(salen)(PPh(3))(Cl) (salen(2-)=N,N'-ethylenebis(salicylideneiminato dianion) using [NEt(4)]OH as a phase transfer agent led to the formation of a stable, N-coordinated nitrite ion complex (Ru(III)-NO(2)) that was characterized by single crystal X-ray diffraction. This reaction also resulted in nitration of the two phenolic rings of the salen ligand, which was unexpected given the basic conditions. With sodium nitrite, the Ru(III)-nitro complex was formed, but no ring nitration was observed. Thus, in a non-acidic medium, the combination of nitrite with redox active metal centers may provide a route to the nitration of phenolic derivatives. Possible mechanisms of this unusual reaction having potential relevance to aromatic nitrations in biological systems are discussed. This is also the first report of the crystal structure of a Ru(III)-nitro complex, a species that has been suggested to be unstable and prone to rapid disproportionation.

Properties of vacuum evaporated vapour chopped polyaniline thin film: effect of synthesis method

The paper reports optical properties and adhesion of polyaniline thin film prepared by vacuum evaporated polyaniline powder synthesized in acidic and nonacidic medium respectively. The effect of vapour chopping on its optical and adhesion properties is also studied. Maximum transmittance 85% and 90% was obtained for polyaniline thin film deposited from polyaniline powder synthesized from nonacidic and acidic medium respectively. Due to non-acidic medium, the film showed absorption peak at 420 nm, whereas due to acidic medium it shifts below 350 nm. Refractive index of PANI from nonacidic medium is higher than the refractive index from acidic medium. After vapour chopping the refractive index decreases and transmittance increases. Adhesion of the film measured by direct pull of method was higher due to acidic medium ∼68 Kgf/cm2 After chopping adhesion of the film increases. Polyaniline thin film deposited from acidic polyaniline powder are more stable and gives lower refractive index with higher adhesion. Vapour chopping also improves the properties of these thin films.

Hydrogenation of pyrrole derivatives: Part V. Poisoning effect of nitrogen on precious metal on carbon catalysts

Poisoning of different precious metals on carbon catalysts (Pd/C, Ru/C and Rh/C) was observed in the hydrogenation of some pyrrole derivatives, under mild reaction conditions, in non-acidic medium. In all reductions, the catalysts were poisoned by the hydrogenated products (pyrrolidines) more strongly than by the reactants (pyrroles). A comparison concerning poison sensitivity of the catalytic metals was also made.

Diastereoselective heterogeneous catalytic hydrogenation of N-heterocycles : Part II. Hydrogenation of pyrroles

High diastereoselectivities were obtained in the heterogeneous catalytic hydrogenation of a chiral pyrrole derivative with complete conversion, in non-acidic medium. The effects of catalytic metals, temperature and solvents on the conversion and the diastereomeric excess (d.e.) were investigated. In the hydrogenation of N-(1′-methylpyrrole-2′-acetyl)-( S)-proline methyl ester over rhodium on carbon, in methanol, at 20 bar and room temperature (RT) the highest d.e. was 95%. This is a successful example of a diastereoselection in the saturation of pyrrole ring.

Rate and Stereoselectivity Changes During Hydrogenation of n-Heterocycles

High diastereoselectivities were obtained in the heterogeneous catalytic hydrogenation of chiral pyrrole and pyridine derivatives with complete conversion, in non-acidic medium. The products of the hydrogenations, secondary and tertiary amines act as catalyst modifiers, increasing the d.e. values in the last period of the reactions.

Diastereoselective heterogeneous catalytic hydrogenation of N-heterocycles. Part I. Hydrogenation of pyridines

High diastereoselectivities were obtained in the heterogeneous catalytic hydrogenation of chiral picolinic and nicotinic acid derivatives with complete conversion, in non-acidic medium. The effects of catalytic metals, solvents, temperature and pressure on the conversion and the diastereomeric excess (d.e.) were investigated. The hydrogenation of N-picolinoyl-( S)-proline methyl ester ( 1) resulted in 79% d.e. over 10% Pd/C, in methanol, at moderate pressure and temperature (50 bar, 50°C). Very high d.e. (94%) was achieved in the saturation of N-nicotinoyl-( S)-proline methyl ester ( 2) under similar conditions. The hydrogenation of quaternized 1 took place already at room temperature (RT) and 20 bar with almost complete diastereoselectivity (98%), over palladium on carbon, in methanol. These are successful examples of a diastereoselection in the hydrogenation of prochiral pyridines.

A mild dehydrazination reaction of arylhydrazines using nitric oxide in the presence of oxygen

A new dehydrazination reaction of arylhydrazines using nitric oxide and oxygen as a mild nitrosating agent is described. Taking advantage of non-aqueous and non-acidic medium appears to cause this novel selectivity as a counterpart of the azide synthesis by the conventional methods. The generality and reaction mechanism were also investigated.

Hydrogenation of pyrrole derivatives Part III. Hydrogenation of methyl 1-methyl-2-pyrroleacetate

A new hydrogenation method for the saturation of the pyrrole ring has been applied in the hydrogenation of methyl 1-methyl-2-pyrroleacetate in non-acidic medium. Various catalytic metals and solvents have been screened. High conversion and selectivity were achieved with rhodium and ruthenium catalysts. In palladium catalyzed hydrogenations the selectivity was improved by appropriate solvents.

Hydrogenation of pyrrole derivatives. Part IV. Hydrogenation of 1-methylpyrrole

The heterogeneous catalytic hydrogenation of 1-methylpyrrole was investigated in non-acidic medium. Various supported noble metal catalysts and solvents have been screened. The highest activities were provided by rhodium and ruthenium catalysts. In palladium mediated hydrogenations the activity of the catalyst was increased by appropriate solvents. The reactivity of 1-methylpyrrole was compared with that of pyrrole and its derivatives hydrogenated previously.

Hydrogenation of pyrrole derivatives. II. Hydrogenations over supported noble metal catalysts

The heterogeneous catalytic hydrogenation of 1-methyl-2-pyrroleethanol resulted in 1-methyl-2-pyrrolidineethanol, an important and valuable pharmaceutical intermediate. Various noble metal catalysts on different supports have been screened. The best results were achieved with a carbon supported rhodium catalyst, in non-acidic medium, under mild reaction conditions (6 bar, room temperature). Ruthenium on carbon also showed high activity in this hydrogenation.

Hydrogenation of pyrrole derivatives I. Hydrogenations over palladium

The heterogeneous catalytic hydrogenation of 1-methyl-2-pyrrole ethanol resulted in 1-methyl-2-pyrrolidine ethanol, an important and valuable pharmaceutical intermediate. In non-acidic medium, with carbon supported palladium catalyst, applying solvent mixtures and mild reaction conditions (6 bar, 80°C) high conversion and selectivity were obtained. This hydrogenation is part of a newly developed and industrially feasible synthesis.

Purification of nucleotide-linked peptide

Affinity labeling of nucleotide-binding enzymes/proteins with 32P-labeled nucleotides is a powerful technique to identify nucleotide-binding proteins as well as to radiolabel the specific binding site. We have used this approach for labeling a nucleotide-binding domain in DNA polymerase and have isolated peptides bearing the linked nucleotides. The method used for separating tryptic peptides on hydrophobic matrices with an acetonitrile gradient in 0.1% trifluoroacetic acid as eluent results in loss of radioactivity, presumably through dissociation of the cross-linked nucleotide. This can be averted by the use of a non-acidic medium in the peptide purification protocol. We have devised a relatively simple procedure to concentrate the nucleotide-linked peptides by chromatography on DEAE-Sephadex A25. Most neutral and basic peptides as well as free nucleotides are removed by eluting the DEAE-Sephadex column with 0.2 M ammonium bicarbonate. The nucleotide-linked peptide is then eluted with 0.6 M ammonium bicarbonate. Radioactivity in the collected fractions is conveniently determined by scintillation counting. Labeled peptide in the 0.6 M ammonium bicarbonate eluate can be purified on a C 4 reversed-phase column with an acetonitrile gradient in phosphate buffer (pH 6.8). By this procedure, 32P-labeled nucleotide linked with protein/peptide can be quantitatively purified with minimum loss.

Fluorination of dimethyl sulphide. Formation of the fluorodimethylsulphonium cation, [Me2SF]+, and dimethylsulphur difluoride, Me2SF2

The controlled reaction of dimethyl sulphide with xenon difluoride in a non-acidic medium gives rise via CH2FSMe to a product best formulated as [Me2SCH2SMe]+[F(HF)n]–. In HF solution at –23 °C, however, the reaction affords the fluorodimethylsulphonium cation, [Me2SF]+, solid derivatives of which have also been prepared by the reaction of XeF2 with Me2S·A (A = BF3 or AsF5); the species have been characterised by their 1H and 19F n.m.r. and vibrational spectra. With CDCl3 as a diluent, Me2S reacts with an excess of AgF2 at –23 °C to provide the first evidence of the thermally unstable dimethylsulphur difluoride, Me2SF2. The 1H and 19F n.m.r. spectra have served to characterise the new compound and to chart its decomposition (to CH2FSMe) and other reactions.

Comportement electrochimique et reactivite du systeme Ag(II)-Ag(I)-bipyridine dans le carbonate de propylene

The electrochemical behaviour of silver(I)- and silver(II)-bipyridyl complexes has been investigated using voltammetry, cyclic voltammetry and coulometry in propylene carbonate. In unbuffered non-acidic medium, when the stoichiometry of the solutions is C L/C Ag = 2, the Ag I(bipy) + concentration is low; the preponderant species is Ag I(bipy) 2 +. Under such conditions, the Ag II(bipy) 2 2+/Ag I(bipy) 2 + couple hs a reversible behaviour and is one of the must powerful oxidants used in the solvent ( E ′° = 0.790 V vs E Fc ′° + Fc). As a function of the acidity level of the solutions, one observes the oxidation of either Ag I(bipy) + or Ag + in the presence of the protonated ligand to complexed Ag(II). The silver(II) species produced oxidizes water and the excess of ligand (C L/C Ag > 2).