A Grafting Study on Partially Dehydrochlorinated Poly(vinyl chloride) by Atom Transfer Radical Polymerization

HCl elimination in low ratio was first carried out from poly(vinyl chloride) to increase allylic chlorines. Partially dehydrochlorinated poly(vinyl chloride), having a macroinitiator effect, was grafted with tert‐butyl methacrylate via atom transfer radical polymerization in the presence of CuBr/2,2′‐bipyridine at 64°C in tetrahydrofuran. Original poly(vinyl chloride) was also grafted with tert‐butyl methacrylate under the same conditions to compare with that of partially dehydrochlorinated poly(vinyl chloride). The graft copolymers were characterized by elemental analysis, FTIR, ¹H and ¹³C‐NMR, differential scanning calorimetry, and gel permeation chromatography (GPC). Thermal stabilities of the graft copolymers were investigated by thermogravimetric analysis as compared with those of the macroinitiators.     

Molecular resistivities in organic polyenic wires: I. A one-dimensional photoconduction charge transfer model

In the present work we have developed a one-dimensional photoconduction charge transfer model, which allows us to determine the resistivities associated to π-conduction molecular channels of organic polyenic wires. In order to calculate the charge transmission coefficient through the conductor molecular wire, our model is based on the scattering process of electrons in metals according to Landauer's one-dimensional conductor approach. This model can be applied to those D–bridge–A molecular systems, constituted by an electron-donor group (D), an electron-acceptor group (A) and a polyenic conductor molecular bridge, which present a photoinduced charge transfer absorption band. According to the present model, molecular resistivities and resistances in the charge transfer excited state of a series of polyenic compounds containing several kinds of electron-donor groups and CO, as an electron-acceptor group, have been calculated by means of the INDO/S-CI method, in the framework of ZINDO semiempirical molecular orbital theory. The calculations allow us to determine the linear and nonlinear contributions to the total molecular resistance of the π-conduction channel in the charge transfer excited state. Linear resistivities for a series of polyenic aldehydes substituted by an electron-donor group (D=–CH₃, –OCH₃, –NH₂ and –N[CH₃]₂) range between 18 and 42 μΩ cm and these results agree with the order of magnitude expected in classic conductors such as metals, nonmetals, and doped polyacetylenic compounds in the ground state.     

Dehydrochlorination of Poly(vinyl Chloride) in Pyridine. 1. Effect of Conditions

Poly(viny1 chloride) (PVC) was dehydrochlorinated thermally in pyridine solution under N₂ atmosphere and the effect of variation of reaction time, temperature, and concentration of PVC in pyridine was studied. The extent of dehydrochlorination (or conversion, x%) increases with an increase in reaction time and temperature, and with a decrease in the concentration of PVC. Incomplete precipitation of dehydrochlorinated PVC (DHPVC) occurs by nonsolvent (methanol). During dehydrochlorination there is no HCl evolution as it forms a pyridine hydrochloride complex which is supposed to act as a catalyst for dehydrochlorination. A possible mechanism has been proposed. Chain scission and cross-linking reactions are responsible for the molecular weight changes that take place during the reaction.     

Chemistry of acetals Communication 16. Ways of synthesizing symmetrical and unsymmetrical bifunctional polyenic compounds

Summary Some symmetrical and unsymmetrical bifunctional polyenic compounds were synthesized; they included diphenyl polyenes, polyenic diketones and dinitriles, dibromo polyenic dicarboxylic esters, polyenic cyano acetals and keto acetals, polyenic keto esters, and cyano polyenic carboxylic esters.     

Spectral properties and conformations of nonlinear ketocyanines

The electronic transitions in molecules of the ketocyanine dyes (polyenic ω,ω′-bisamino ketones) were calculated by quantum chemical methods. Satisfactory agreement was obtained between the experimental bands of the S-S absorption spectra and calculated electronic transitions for the ketocyanine with the central pyranone moiety and the corresponding salt assuming an acute angle between the chromophores and for the ketocyanine with the central pyridone moiety assuming an obtuse angle between the chromophores. Such molecular conformations were confirmed by the gNOESY ¹H NMR data for these dyes. The difference in the conformations of the dyes with the pyranone and pyridone moieties is due, most likely, to steric hindrance created by the central methyl groups in the molecules of the latter. The salts corresponding to these dyes have similar conformational differences. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1954–1958, October, 2007.     

聚氯乙烯-丙烯酸丁酯接枝共聚物的结构表征

以通用聚氯乙烯(PVC)和脱氯化氢PVC树脂为基体,采用悬浮溶胀接枝共聚法合成聚氯乙烯-丙烯酸丁酯接枝共聚物,对脱氯化氢PVC和接枝共聚物的结构进行了表征.结果表明,以碱液为介质加热PVC能脱除少量氯化氢,得到以链节数为2,3,4的共轭双键为主的不饱和结构,而树脂的分子量变化不大;在相同接枝反应条件下,采用脱氯化氢PVC与丙烯酸丁酯接枝共聚可以提高接枝率和接枝效率;PVC接枝共聚物的特性粘度随接枝率增加而增加,其重均分子量和分子量分布指数均大于接枝所用的PVC树脂.     

The discolouration of PVC—I : Correlation between the dehydrochlorination and discolouration of PVC

A mathematical relation has been derived, on the basis of the kinetics of polyenic sequence formation, to describe the correlation between discolouration and dehydrochlorination in the thermodegradation of PVC. According to this, there is a close connection between the hydrochloric acid split off and the degree of discolouration, as well as the number of polyenic sequences. Calculations based on measurements in nitrogen substantiate the correctness of the expression. By the use of this relation, with knowledge of the induction periods of stabilized PVC samples, the total amount of hydrochloric acid formed can be calculated from the measured degrees of discolouration.     

两个具有强双光子荧光的有机硼化合物

以二米基硼为电子受体, 苯乙烯基噻吩为共轭桥, 合成了两个新的稳定的有机硼化合物: 反式,反式-2-二米基 硼-5-{2-[4-(2-噻吩乙烯基)苯基]乙烯基}噻吩(1)和反式,反式-1,4-二-[2-(5-二米基硼噻吩)乙烯基]苯(2). 前者为不对称结构的偶极分子, 后者为对称的A-π-A型四极分子. 对称性不同的化合物表现出不同的双光子吸收性质. 对于偶极分子1, 单双光子吸收达到的激发态能级接近, 而对于四极分子2, 双光子吸收达到的激发态则比单光子吸收所达到的激发态高出0.35 eV. 在波长为710到 900 nm范围的飞秒脉冲激光激发下, 化合物1和2在THF溶液中都可以发出很强的绿色上转换荧光 (1, λ_max＝505 nm; 2, λ_max＝513 nm). 用双光子荧光法测得A-π-A型化合物2在775 nm处的双光子吸收截面达1340 GM.     

Synthesis of functionalized N-methylpyrroles

The preparation of some new N-methylpyrroles is shown. These heterocyclic compounds were used to synthesize polyenic substances with polysubstituted pyrrole rings.     

电子等排体的噻吩多烯与苯多烯同系递变的比较Ⅱ

为了比较噻吩多烯和苯多烯三岔共轭体系的性能,合成了三个系列带两个拉电子基团的噻吩多烯三岔化合物(TDn,TEn,TFn),测定了它们在环已烷和乙醇中的电子吸收光谱。实验表明,带两个拉电子基团的噻吩多烯三岔共轭化合物的电子吸收光谱频率也都遵守同系线性规律,相关系数Υ>0.99。与相应的苯多烯化合物的电子光谱相比,吸收峰普遍地红移一个插烯双键所引起的红移数值。相应的同系直线相距很近。△λ_(th)/△λ_E值为0.83-1.10。第一个拉电子基团的引入,化合物的电子吸收峰红移30nm左右,但当第二个拉电子基团引入时,电子吸收峰仅红移3—17nm,其作用只相当于一个取代基。     

Synthesis,Optical and Photovoltaic Properties of Porphyrin Dyes

The synthesis and optical absorption of a series of porphyrins, and the photoelectrochemical properties of TiO₂ solar cells sensititized with these porphyrins was investigated. The different types of porphyrins studied are designated by numbers: the reference compound 1 (Zinc(II) 5,15-bis(4-carboxylphenyl)porphyrin), porphyrin substituted with one triarylamine unit 2, and porphyrin substituted with two triarylamine units 3. The UV-Vis absorption spectra reveal that the substitutions result in large redshifts in both the Soret band (～ 60 nm) and the Q bands (～ 125 nm), as well as enhancement of optical absorption. The enhancement is even more pronounced in the long-wavelength region of 575–725 nm, where the absorption of porphyrin 3 is eight times that of porphyrin 1. The photoelectrochemical properties of the porphyrins were also studied by constructing porphyrin-sensitized TiO₂ solar cells. Under standard AM 1.5 sunlight, the porphyrin 1 cell yields a short-circuit current of ～ 1.26 mA/cm², an open-circuit voltage of ～ 0.564 V, and a fill factor of ～ 61%. The incident photon-to-current conversion efficiency is ～ 24% for porphyrin 1 and ～ 5–7% for porphyrins 2 and 3 at the Soret peak.     

Aza-analogues of extended tetrathiafulvalenes

The phosphoramidate-like reaction of 1,3-dithiole derived N-(diethoxyphosphinyl)hydrazones with formyl derivatives of 1,3-dithiole affords the longest aza-analogues of extended tetrathiafulvalenes with a polyenic spacer reported to date. Their structural and electrochemical properties are discussed.     

Transformations of halocyclopropanes—VII : Reactions of 7,7-dichlorobicyclo[4.1.0] heptane with carbanions

The reactions of 7,7-dichlorobicyclo[4.1.0] heptane 1 were carried out with C-H acids in the presence of t- BuOK in DMSO. The respective syn-7-chlorobicyclo[4.1.0] heptane derivatives 3 were the major products of the reactions with diethyl malonate and ethyl cyanoacetate. The dehydrochlorinated material α-bicyclo[4.1.0] hepten-5-yl-α-phenylpropionitrile 5c, was obtained in good yield in the reaction with α-phenylpropionitrile.     

The acylation of 5H-2,3-benzodiazepines

The products obtained from the acylation of 4-phenyl-5$\text{H}$-2,3-benzodiazepine (5) are strongly dependent on the nature of the acylating agent and the reaction conditions. Reaction with acid anhydrides followed by a nucleophile gives the 1-substituted 2-acylbenzodiazepines (10) and (11) while reaction with acyl or sulphonyl halides either induces a ring transformation to give the 3-phenylisquinoline $\text{N}$-imine salts (12) or results in the formation of the acylated dimer (13) $\text{via}$ a dehydrochlorinated intermediate (15).     

几种多氮杂环高能化合物的光电子能谱与紫外吸收光谱

多氮杂环化合物由于含氮量高, 具有很高的生成焓, 而且分解产物一般不会对环境造成污染, 因此这类化合物用于环境友好的炸药和推进燃料的前景十分诱人, 成为当前高能量材料的研究热点之一. 利用紫外光电子能谱实验手段和量子化学计算研究了四种多氮杂环化合物[1H-tetrazole (1), 5-aminotetrazole (2), 1,5-diaminotetrazole (3), 1,4-bis(1-methyltetrazol-5-yl)-1,4-dimethyl-2-tetrazene (4)]的电子结构, 提供了这些化合物的电离能: 实验结果表明四个化合物的第一电离能分别为: 11.22, 9.40, 9.27, 9.18 eV; 同时报道了这四个化合物在乙氰溶液中的紫外吸收光谱: 化合物 1～3 均只有一个紫外吸收峰带, 分别为193, 216, 218 nm, 化合物 4 在230和298 nm出现了两个吸收带.     

Light absorption of dye aggregates. Coupled oscillator and electron gas model for aggregates formed from polyene type monomers

A modified coupled oscillator model using extended dipoles in place of each double bond is found to be superior to the point dipole model and gives absorption shifts for polyenic dye aggregates in agreement with electron gas calculations and with experimental evi     

Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. XI. Synthesis of 2H-pyrano[3,2-g]benzothiazole derivatives

Cycloaddition of dichloroketene to N,N-disubstituted 6-aminomethylene-5,6-dihydro-2-phenylbenzothiazol-7-(4H)ones gave in good yield N,N-disubstituted 4-amino-3,3-dichloro-3,4,5,6-tetrahydro-8-phenyl-2H-pyrano[3,2-g]benzothiazol-2-ones II, which are derivatives of the new heterocyclic system 2H-pyrano[3,2-g]benzothiazole. Dehydrochlorination with triethylamine of II afforded N,N-disubstituted 4-amino-3-chloro-5,6-dihydro-8-phenyl-2H-pyrano[3,2-g]benzothiazol-2-ones III in good to moderate yield. The dimethylamino adduct was dehydrochlorinated in high yield by refluxing in toluene, whereas the diisopropylamino adduct gave in low yield 6-(2,2-dichloroethylidene)-5,6-dihydro-2-phenylbenzothiazol-7-(4H)one with the triethylamine treatment. The dehydrochlorinated product IIId (NR₂ = pyrrolidino) was obtained directly in low yield by cycloaddition of dichloroketene to the corresponding enaminone. Full aromatisation of IIIa,g [NR₂ = N(CH₃)₂ and N(CH₃)C₆H₅, respectively] to the corresponding N,N-disubstituted 4-amino-3-chloro-8-phenyl-2H-pyrano-[3,2-g]benzothiazol-2-ones was accomplished with DDQ in refluxing benzene.     

Identification of putative and potential cross-reactive chickpea (Cicer arietinum) allergens through an in silico approach

BackgroundAllergy has become a key cause of morbidity worldwide. Although many legumes (plants in the Fabaceae family) are healthy foods, they may have a number of allergenic proteins. A number of allergens have been identified and characterized in Fabaceae family, such as soybean and peanut, on the basis of biochemical and molecular biological approaches. However, our understanding of the allergens from chickpea (Cicer arietinum L.), belonging to this family, is very limited.ObjectiveIn this study, we aimed to identify putative and cross-reactive allergens from Chickpea (C. arietinum) by means of in silico analysis of the chickpea protein sequences and allergens sequences from Fabaceae family.MethodsWe retrieved known allergen sequences in Fabaceae family from the IUIS Allergen Nomenclature Database. We performed a protein BLAST (BLASTp) on these sequences to retrieve the similar sequences from chickpea. We further analyzed the retrieved chickpea sequences using a combination of in silico tools, to assess them for their allergenicity potential. Following this, we built structure models using FUGUE: Sequence-structure homology; these models generated by the recognition tool were viewed in Swiss-PDB viewer.ResultsThrough this in silico approach, we identified seven novel putative allergens from chickpea proteome sequences on the basis of similarity of sequence, structure and physicochemical properties with the known reported legume allergens. Four out of seven putative allergens may also show cross reactivity with reported allergens since potential allergens had common sequence and structural features with the reported allergens.ConclusionThe in silico proteomic identification of the allergen proteins in chickpea provides a basis for future research on developing hypoallergenic foods containing chickpea. Such bioinformatics approaches, combined with experimental methodology, will help delineate an efficient and comprehensive approach to assess allergenicity and pave the way for a better understanding of the biological and medical basis of the same.     

Zn(II)-containing metallo-supramolecular polymers: synthesis,photophysical and electrochemical properties

Abstract

Two novel building blocks M1, M2 with different electronic structures, were synthesized based on 2,2′:6′,2″-terpyridine modified with cyano-p-phenylenevinylene (CN-PV) and carbazole moieties through Knoevenagel condensation and Suzuki coupling, respectively. Directed by transition metal ion Zn²⁺, the metallo-homopolymers P1, P2 and metallo-copolymer P3 were obtained via self-assembly polymerization. The structures of the monomers and metallo-supramolecular polymers were fully characterized by MS, ¹H-NMR and ¹³C-NMR. Meanwhile, the UV–vis absorption, photoluminescence (PL) and electrochemical properties of these compounds were systematically investigated. With respect to that of the monomers, both the UV–vis absorption and PL spectra of the polymers are significantly red-shifted. The resulting metallo-supramolecular polymers show similar double absorption peaks (342, 418?nm for P1, 339, 410?nm for P2, and 332, 412?nm for P3), which is caused by the π–π* transition and intramolecular charge transfer (ICT). Further, all the polymers display red-orange emission in toluene and narrow electrochemical energy gaps of 1.46, 1.65 and 1.48?eV for P1, P2, and P3, respectively.     

Design,photochemistry and antibacterial evaluation of novel light-harvesting antenna

Abstract

Novel light-harvesting compound 6, based on 1,8-naphthalimide donors and perylenediimide acceptor were synthesized. The light-harvesting compound 6 showed intensive absorption band in range between 390 and 560?nm, that is 50?nm wider in comparison with the absorption of the model perylene dye. The novel antenna 6 has a higher ability to collect photons from environment in comparison with the single perylene diimide dyes. The chosen fluorophore units are suitable donor–acceptor pair for light-harvesting materials which was in agreement with their good antibacterial activity.