3-methylthiophene self-assembled monolayers on planar and nanoparticle Au surfaces

In this article the adsorption of 3-methylthiophene on planar and nanoparticle Au surfaces is investigated. The resulting systems are compared with a benchmark system based on 1-decanethiol. The characterization data collected evidence the formation of a packed 3-methylthiophene SAM on the planar surface. In particular, spectroscopic investigations suggest that 3-methylthiophene aromatic system is not adsorbed on the surface through the pi-electron system but rather through the S atom alone. On the other hand, the behavior of 3-methylthiophene on nanoparticle surfaces is notably different from that of the alkanethiol. Only a limited fraction of the surface of Au nanoparticles results to be actually coated after purification; this notwithstanding, the nanoparticle growth seems to be strongly influenced by the presence of such a labile encapsulating agent.     

甲基噻吩在HY分子筛上的吸附、脱附及转化行为

由NH₄Y分子筛制备了HY分子筛,运用N₂吸附、NH₃-TPD和Py-FTIR等手段表征HY分子筛的物化性能;采用智能重量分析仪(IGA)方法研究了甲基噻吩(2-甲基噻吩、3-甲基噻吩)在HY分子筛上的吸附-脱附行为;采用程序升温脱附-质谱(TPD-MS)联用手段研究了甲基噻吩在HY分子筛上的转化行为。结果表明,在200 ℃下 2-甲基噻吩和3-甲基噻吩在HY分子筛中的强B酸上发生强化学吸附作用,与B酸结合后生成了甲基噻吩的碳正离子结构进而发生了歧化反应、脱烷基反应以及裂化反应;与2-甲基噻吩不同的是,3-甲基噻吩与HY通过一定的氢转移反应生成了3-甲基四氢噻吩,且200 ℃吸附条件下3-甲基噻吩比2-甲基噻吩更容易发生裂化反应。     

焦化汽油中硫化物类型分布的气相色谱-硫化学发光检测方法

建立了焦化汽油中硫化物类型分布的气相色谱-硫化学发光检测分析方法。考察了色谱条件对焦化汽油中各种硫化物分离的影响,定性了某焦化汽油中的74个硫化物。以硫化氢、乙硫醇、正丙硫醇、噻吩、2-甲基噻吩、2-乙基噻吩、2-丙基噻吩、碳四噻吩(tR=40.28 min)、苯并噻吩、甲基苯并噻吩(tR=58.13 min)的保留时间为尺度,计算了焦化汽油中各种硫化物的保留指数,并可推广到其他类型的汽油馏分中各种硫化物保留指数的计算,为仅能提供硫化物信息的仪器提供了可靠的定性依据。焦化汽油中几种主要硫化物(异丙硫醇、正丙硫醇、正丁硫醇、2-甲基噻吩、3-甲基噻吩、2,4-二甲基噻吩、2,3,4-三甲基噻吩)含量测定值的相对标准偏差均小于5%。当信噪比为3时,测得硫的检测限为0.05 mg/L。研究发现:同其他类型的汽油相比,焦化汽油的硫含量较高且所含硫醇比例明显偏高,2-甲基噻吩和3-甲基噻吩的含量差别较大。该法可为加氢脱硫催化剂和工艺的研究提供数据。     

FeCl3-catalyzed efficient synthesis of di(5-methylfuran/thiophen-2-yl)isatin analogues

A simple, inexpensive, environmentally friendly, and high yield protocol is described for the synthesis of (5-methylfuran/thiophene-2-yl)isatin by the reaction of 2-methylfuran/2-methylthiophene with isatin/isatin imine in the presence of FeCl₃. The present protocol is ideal for the direct introduction of 2-methylfuran/2-methylthiophene onto isatin at 3-position with complete regioselectivity.     

<Emphasis Type="Italic">In situ</Emphasis> spectroelectrochemical study of dissolved oligomer products formed in the electrochemical polymerization of 3-methylthiophene

An in situ spectroelectrochemical study was carried out on the formation of 3-methylthiophene oligomer radical-cations (monomer, dimer, and trimer) and the 3-methylthiophene dihydrocation in the solution bulk during the electrochemical synthesis of a poly-3-methylthiophene coating on a conducting glass electrode. A dependence of the concentration of products formed on the cation radius (Li⁺ and Na⁺) and nature of the anion ( \textClO₄^- {\text{ClO}}_4^{-} and \textBF₄^- {\text{BF}}_4^{-} ) of the base electrolyte was established. The conversion of charged components into neutral dimers and tetramers of 3-methylthiophene after termination of the anodic polymerization was shown in accord with reported results on the electrochemical polymerization of thiophenes.     

Electrosynthesis and characterization of poly(3-methylthiophene) on different substrates

 We report on the study of the electropolymerization of 3-methylthiophene onto Pt, p-Si and indium-tin oxide deposited on polyester using quartz crystal microgravimetry, electrochemical and spectroelectrochemical measurements. We observe that potential variation during the galvanostatic electrodeposition is correlated with the nucleation process. The mass variation of poly(3-methylthiophene) is linear with the amount of the electrochemical charge whereas the absorbance variation curve shows two distinct slopes. The latter result has been explained in terms of conjugation length variation during polymer growth. Scanning electron microscopy analysis allowed the detection of morphological changes from a dense and compact structure to an open morphology when the poly(3-methylthiophene) film thickness increases. The roughness of the films did not change considerably with the substrate, as observed by atomic force microscopy. Absorption and photocurrent spectra at different film thicknesses show a shift of the peaks to lower wavelengths when the thickness increased, thus confirming the decrease of mean conjugation length in thicker films. Received: 1 September 1998 / Accepted: 11 November 1998     

2-甲基噻吩光异构化成3-甲基噻吩的理论研究

用CASSCF方法以6-31G基组研究了2-甲基噻吩光异构化为3-甲基噻吩的光化学反应和基态(S₀)及三重激发态(T₁)的相关势能面.反应主要发生在三重态(T₁)上,其间经历了两个双自由基,1个三元环中间体及4个过渡态.沿着反应路径找到了2个T₁/S₀势能面交叉点,其结构都类似于双自由基.在第二个T₁/S₀势能面交叉点附近由T₁向S₀的系间窜越(ISC)最为有利.     

Influence of the texture of chromia catalysts on their activity in synthesis of 2-methylthiophene

The texture of Cr₂O₃-K₂O/Al₂O₃catalysts containing oxides of rare earth elements (REE) was studied. The catalysts are used for the synthesis of 2-methylthiophene by the reaction of H₂S with n-pentane or piperilene. The heterocyclization of n-pentane is a consecutive reaction involving a step of dehydrogenation of initial hydrocarbon. At this step the texture of the catalyst affects the yield of 2-methylthiophene. The yield of 2-methylthiophene obtained from piperilene and I₂S is independent of the catalyst texture.     

The effect of the nature of the dopant on the sensor response of poly(3-methylthiophene) films

The effect of the nature of the dopant on the response of a sensor array based on films of poly(3-methylthiophene) under the influence of various organic solvents was studied. It was established that the electroconductivity of the polymer can both increase and decrease under the influence of the analytes. It was suggested that the main factors determining the magnitude of the response of poly(3-methylthiophene) are the ratio of the number of radical-cationic and dicationic states in the polymer, which depends on the nature of the dopant-anion, and also the polarity of the analyte. It was shown that the polymer has high sensitivity to chloroform vapor, which makes sensor arrays based on poly(3-methylthiophene) selective with respect to this analyte. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 331–338, November–December, 2006.     

Unusual chromic and doping behavior of ether substituted polythiophenes

Poly[3-(oligoethylene oxide)-4-methylthiophene] is doped by HCl in aqueous solution in the absence of oxygen and undergoes dramatic solvatochromism in water-ethanol mixtures.     

Electrochemical copolymerization of 9,10-dihydrophenanthrene and 3-methylthiophene and characterization of their copolymer with tunable fluorescence properties

Electrochemical copolymerization of 9,10-dihydrophenanthrene and 3-methylthiophene was successfully achieved in boron trifluoride diethyl etherate by direct anodic oxidation of the monomer mixtures. The structure and properties of the copolymers were investigated with ultraviolet–visible, Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, fluorescence spectra, and thermal analysis. The novel copolymers had the advantages of both poly(9,10-dihydrophenanthrene) and poly(3-methylthiophene), such as good electrochemical behavior, good mechanical properties, and high electrical conductivity. Fluorescence spectroscopy studies revealed that the copolymers had good fluorescence properties, and the emitting properties of the copolymer could be parameters by changing the feed ratio of the monomer mixtures during the electrochemical polymerization.     

Electrochemical Behavior of Polythiophene Films: Effect of Electrolyte Concentration and the Nature of the Alkyl Substituent

The electrochemical behavior of poly(3-methylthiophene) and poly(3-octylthiophene) films in solutions of 0.05–0.5 M LiClO₄ in acetonitrile is studied using cyclic voltammetry and chronoamperometry. An analysis of data on the current relaxation following a film perturbation by a pulsed small voltage reveals the presence of two constituents of the current relaxation for either polymer, each constituent exponentially depending on the time. Effect of the electrode potential and electrolyte concentration on the current relaxation parameters are studied. Results of additional studies of poly(3-methylthiophene) films by a faradaic impedance method conform to the chronoamperometry data and permit a more reliable interpretation of them.     

Synthesis of trisubstituted thiophenesvia a halogen dance reaction at 2-bromo-5-methylthiophene

Summary A new example of a selective halogen dance reaction was observed upon lithiation of 2-bromo-5-methylthiophene withLDA under appropriate reaction conditions. A series of 2-substituted 3-bromo-5-methylthiophenes was prepared by reacting the thus selectively generated intermediate 3-bromo-2-lithio-5-methylthiophene with various electrophiles to study scope and limitations of the reaction.Dedicated to Prof. emeritusHans Suschitzky, University of Salford, UK, on the occasion of his 80^th birthday     

Activity of palladium sulfide catalysts in the reaction of gas-phase hydrogenation of 2-methylthiophene

In the interaction of hydrogen with 2-methylthiophene in the gas phase over palladium sulfide catalysts at 180–260?C and 0.1–0.8 MPa, the saturation of the thiophene ring resulting in 2-methylthiolane and the hydrogenolysis of 2-methylthiophene occurs. When the conversion is lower than 60%, these reactions occur independently; at higher conversions, methylthiolane also undergoes hydrogenolysis. The specific catalytic activity of PdS supported on γ-Al₂O₃, TiO₂, and carbon and without support is much lower in the hydrogenation of 2-methylthiophene than the activity of PdS supported on SiO₂, aluminosilicate, and zeolite HNaY having strong Brönsted acid surface sites.     

STUDIES OF MECHANISM OF 2-METHYLTHIOPHENE AND THIOPHENE FORMATION FROM N-PENTANE AND HYDROGEN SULPHIDE USING 14C

Abstract

The mechanism of 2-methylthiophene formation from n-pentane and hydrogen sulphide over Cr-containing oxide catalyst is studied by using the Kinetic-Isotope method. The experiments were carried out in pulse system in He as a carrier gas (535° and 3 atm.) using ¹⁴C-labelled pentene and n-pentane. The reaction products were analyzed by radiochromatography. It is shown the 2-methylthiophene formation from n-pentane and hydrogen sulphide proceeds largely via consecutive dehydrogenation of n-pentane to pentenes, pentadiene followed by interaction with hydrogen sulphide. Thiophene is largely as a result of C₄-hydrocarbon interaction with hydrogen sulphide. A general scheme of the mechanism of 2-methylthiophene and thiophene formation is suggested.     

On the Side-Chain Bromination of 3-Methylselenophene and 3-Methylthiophene

3-Bromomethylselenophene can be prepared from 3-methyl-selenophene, N-bromosuccinimide and azo-bis-isobutyronitrile in carbon tetrachloride in 25% yield with the reversed addition method described in this paper. The method also gives consistently high yields of 3-bromomethylthiophene (70–75%) when applied on 3-methylthiophene.     

Competition between Polymerization and Dissolution of Poly(3-methylthiophene) Films

Films of electrically conducting polymer, poly(3-methylthiophene), are dissolved in monomer-free solutions at positive potentials to become thin, whereas they are polymerized in monomer-rich solutions at the same potentials as for the dissolution. A question arises whether they are dissolved or polymerized in solutions including a given concentration of the monomer when a positive potential is applied to the film. Conditions of the competition between the polymerization and the dissolution were searched at potentiostatic experiments for poly(3-methylthiophene) films at various concentrations of monomers and potentials. The dissolution prevailed over the polymerization as the concentration decreased and the potential was less positive. Chronoamperometric currents exhibited oscillation under the competition conditions. The oscillation was explained in terms of the Lotka–Volterra model for a simple oscillation reaction, in which competitive species were the conducting polymer and the monomer.     

New colorimetric and fluorometric chemosensor based on a cationic polythiophene derivative for iodide-specific detection

Electrostatic interactions between anions and a new water-soluble, cationic, affinitychromic poly(3-alkoxy-4-methylthiophene) derivative provide a new tool for a selective optical detection method (colorimetric or fluorometric) for iodide ions.     

Fabrication of the DNA/poly(3-methylthiophene) composite film modified electrode and its application for the study on the voltammetric behavior and determination of 8-hydroxy-2′-deoxyguanosine

Science China Chemistry - A composite film of DNA/poly(3-methylthiophene) (P3MT) modified glassy carbon electrode (GCE) has been fabricated by electro-deposition method. P3MT film was first...     

ELECTROCHEMICAL COPOLYMERIZATION OF DIBENZOFURAN AND 3-METHYLTHIOPHENE IN BORON TRIFLUORIDE DIETHYL ETHERATE

The copolymerization of dibenzofuran(DBF)and 3-methylthiophene(MET)was successfully achieved electrochemically by direct anodic oxidation of the monomer mixtures in boron trifluoride diethyl etherate.The effects of applied polymerization potential and the monomer concentration ratios on the copolymerization were investigated by linear sweep voltammetry and cyclic voltammetry(CV).The structure of copolymer films were investigated by UV-Vis,infrared spectroscopy,thermal analysis.As-formed novel copolymers ...