共查询到20条相似文献,搜索用时 15 毫秒
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Carmit Hertzog‐Ronen Dr. Elena Borzin Yulia Gerchikov Nir Tessler Prof. Yoav Eichen Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(40):10380-10386
Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical‐warfare agents. The detection and identification of alkylating agents is not a trivial issue because of their high reactivity and simple structure. Herein, we report on a new multispot luminescence‐based approach to the detection and identification of alkylating agents. In order to demonstrate the potential of the approach, seven π‐conjugated oligomers and polymers bearing nucleophilic pyridine groups, 1 – 7 , were adsorbed onto a solid support and exposed to vapors of alkylators 8 – 15 . The alkylation‐induced color‐shift patterns of the seven‐spot array allow clear discrimination of the different alkylators. The spots are sensitive to minute concentrations of alkylators and, because the detection is based on the formation of new covalent bonds, these spots saturate at about 50 ppb. 相似文献
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Prasad S. Vijayalakshmi A. Gajbhiye N. S. 《Journal of Thermal Analysis and Calorimetry》1998,52(2):595-607
Ultrafine particle of CoFe2O4 has been synthesized using citrate precursor technique. Thermal decomposition of the citrate
precursor, Co3Fe6O4(C6H6O7)8·6H2O, was investigated by TG, DTA and DTG techniques, gas and chemical analyses and was found
to decompose in one or two major steps depending on the heating rate in static/flowing air atmosphere. In the lower heating
rate (5°C min-1), metastable acetonedicarboxylate complex was isolated with the evolution of CO gas and coordinated water
molecule in the temperature range of 120-220°C. Complete decomposition of the citrate network occurs between 220-330°C with
the simultaneous evolution of CO2 and acetone. However both these steps appeared as simultaneous and/or single step process
(between 120-160°C), when the heating rate is high (10°C min-1 and above). The ultrafine CoFe2O4 particles are observed as
the aggregates having surface area 133.8 m2 g-1 composed of 4.8 nm crystallites. The citrate precursor and the decomposed
products were characterized by IR, NMR, XRD, SEM and surface area measurements.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Dr. Kamran T. Mahmudov Prof. Armando J. L. Pombeiro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16356-16398
Resonance‐assisted hydrogen bonding (RAHB), a concept introduced by Gilli and co‐workers in 1989, concerns a kind of intramolecular H‐bonding strengthened by a conjugated π‐system, usually in 6‐, 8‐, or 10‐membered rings. This Review highlights the involvement of RAHB as a driving force in the synthesis of organic, coordination, and organometallic compounds, as a handy tool in the activation of covalent bonds, and in starting moieties for synthetic transformations. The unique roles of RAHB in molecular recognition and switches, E/Z isomeric resolution, racemization and epimerization of amino acids and chiral amino alcohols, solvatochromism, liquid‐crystalline compounds, and in synthons for crystal engineering and polymer materials are also discussed. The Review can provide practical guidance for synthetic chemists that are interested in exploring and further developing RAHB‐assisted synthesis and design of materials. 相似文献
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无溶剂热分解单源前驱体法制备有机单分子层表面修饰NiS纳米微粒 总被引:2,自引:0,他引:2
纳米微粒由于具有很多特别的物理和化学性质,在光、电、磁、机械等各个领域显示出了广阔的应用前景,所以纳米微粒的制备与性能研究是近年来化学、物理和材料科学中最热门和最前沿的课题之一。尽管目前有多种纳米微粒的制备方法见诸文献报道,但是新的纳米微粒的制备方法依然是人们追求的目标之一。无溶剂合成纳米材料是近年来开始研究的制备纳米材料的新方法,在无溶剂环境中,微粒之间的碰撞基本不发生,微粒生长过程是通过单体加成来实现的,这样就较易得到形状和尺寸单分散的纳米材料。但是采用无溶剂合成纳米材料时通常需要加入捕获剂来控制… 相似文献
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纳米LiAlO2 前驱体的电化学合成 总被引:1,自引:0,他引:1
在35 mmol·L-1 Bu4NBr的乙醇溶液中加入180 mg锂片,采用金属阳极溶解法控制电流为0.2 A电解铝片6 h,同时间断滴入0.9 mL乙酰丙酮,制得纳米LiAlO2的前驱体LiAl(Oet)4-n(acac)n[acac为乙酰丙酮基],其结构经IR, XRD, TEM, TG-DTA表征.实验结果表明电解温度为50 ℃,导电盐Bu4NBr浓度为35 mmol·L-1时电流效率在90%以上.在温度为40 ℃,前驱体浓度为300 mmol·L-1, pH=9.0的条件下,水解6 h得粒径20 nm~30 nm的前驱体干凝胶粉,产率可达94.8%;干凝胶粉在550 ℃煅烧可得纳米LiAlO2粉体. 相似文献
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A Macrocyclic Fluorophore Dimer with Flexible Linkers: Bright Excimer Emission with a Long Fluorescence Lifetime 下载免费PDF全文
Hiroshi Osaki Dr. Chih‐Ming Chou Prof. Dr. Masayasu Taki Dr. Kai Welke Prof. Dr. Daisuke Yokogawa Prof. Dr. Stephan Irle Prof. Dr. Yoshikatsu Sato Prof. Dr. Tetsuya Higashiyama Dr. Shohei Saito Prof. Dr. Aiko Fukazawa Prof. Dr. Shigehiro Yamaguchi 《Angewandte Chemie (International ed. in English)》2016,55(25):7131-7135
Bright fluorescent molecules with long fluorescence lifetimes are important for the development of lifetime‐based fluorescence imaging techniques. Herein, a molecular design is described for simultaneously attaining long fluorescence lifetime (τ) and high brightness (ΦF×?) in a system that features macrocyclic dimerization of fluorescent π‐conjugated skeletons with flexible linkers. An alkylene‐linked macrocyclic dimer of bis(thienylethynyl)anthracene was found to show excimer emission with a long fluorescence lifetime (τ≈19 ns) in solution, while maintaining high brightness. A comparison with various relevant derivatives revealed that the macrocyclic structure and the length of the alkylene chains play crucial roles in attaining these properties. In vitro time‐gated imaging experiments were conducted as a proof‐of‐principle for the superiority of this macrocyclic fluorophore relative to the commercial fluorescent dye Alexa Fluor 488. 相似文献
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Zirconium tungsten oxyfluoride, ZrWO4F2, was firstly synthesized with the precursor route. The composition of the compound was determined by combining the results of ICP and XPS. The indexed powder X-ray diffraction pattern of this compound indicates that it is a pure phase, orthorhombic crystal system, space group D22=P2122 and a=15.32(2)?,b=13.877(7)?,c=8.42(2)?.Combining the results of the DTA-TGA curves from room temperature to 700℃ and XRD patterns in different temperatures the mechanism was revealed during the solid precursor (1) been heated to 700℃. The zirconium tungsten oxyfluoride was considered to be a metastable com-pound. The ascertaining of annealing time and temperature is the key of handling. 相似文献
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The mechanism of the precursor dehydration route was revealed for the synthesis of NTE c-ZrW1.6Mo0.4O8. The hydrate precursor was dehydrated at 473 K and transformed to a NTE cubic compound above 800 K. A novel intermediate phase o-ZrWl.6Mo0.4O8 occurs between the temperature range of 573-800 K. The XRD pattern of novel intermediate was refined with the structural model of LT-ZrMo2O8 by using Rietveld method.The residuals are Rwp=7.80% and Rp=5.79%. The space group is Pmn21 and the lattice parameters are α=0.5917(4)nm, b=0.7273(4) nm, c =0.9148(6) nm, and Z=2. 相似文献
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采用未涂层毛细管柱 (5 5cm× 5 0 μm) ,基于H3 BO3 与 β CD络合成大阴离子作为手性拆分试剂 ,在NaOH Cit溶液中加入 9 0mol/LH3 BO3 与 7 0mmol/L β CD(pH =3 0 )作为运行缓冲液 ,用高效毛细管电泳电导检测法对氯霉素前体 (PCP)进行了拆分研究。考察了影响分离的实验参数 ,同时对其拆分机理进行了初步探讨。结果表明 ,在选择的最佳实验条件下 ,氯霉素前体分子中 4个对映异构体在 2 0min内得到基线分离 ,所建立的方法分离条件简单 ,重现性好。 相似文献
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Synthesis,Properties, and π‐Dimer Formation of Oligothiophenes Partially Bearing Orthogonally Fused Fluorene Units 下载免费PDF全文
Dr. Yutaka Ie Yuji Okamoto Saori Tone Prof. Yoshio Aso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16688-16695
A series of oligothiophenes that incorporate cyclopenta[c]thiophene‐based units bearing spiro‐substituted dialkylfluorene was synthesized. Photophysical measurements indicated that there was no interruption in the conjugation along the oligothiophene backbones, irrespective of the number or position of this unit. Electrochemical measurements showed that the thiophene 7‐mers and 11‐mer exhibit reversible multi‐oxidation waves. The formation of cationic species was clearly observed from UV/Vis/NIR measurements. Furthermore, the UV/Vis/NIR spectra at 223 K under one‐electron oxidation conditions revealed that the unsubstituted thiophene or bithiophene units remained in the absence of intermolecular π–π interactions, whereas the formation of π‐dimeric species was observed for the thiophene 7‐mer containing an unsubstituted terthiophene ( U3 ) unit. Theoretical calculations indicated that the combination of the U3 unit and the all‐trans conformation decreased the intermolecular steric repulsion between the fused cyclopentene ring and its facing thiophene, which may contribute to the formation of the dimeric structure. 相似文献
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Or Dishi Dr. Partha Malakar Dr. Linda J. W. Shimon Prof. Sanford Ruhman Prof. Ori Gidron 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(71):17794-17801
In π-conjugated macrocycles, there is a trade-off between the global and local expression of effects such as aromaticity, with the outcome of the trade-off determined by the geometry and aromaticity of the constituent units. Compared with other aromatic rings, the aromatic character of furan is relatively small, and therefore global effects in macrocyclic furans are expected to be more pronounced. Following our introduction of macrocyclic oligofuran, we present the first synthesis of a series of π-conjugated bifuran macrocycles of various ring sizes, from trimer to hexamer, and characterize them using both computational and experimental methods. The properties of macrocyclic oligofurans change considerably with size: The smaller trimer is rigid, weakly emissive and planar as revealed by its single crystal structure, and displays global antiaromaticity. In contrast, the larger pentamer and hexamer are flexible, emissive, have non-planar structures, and exhibit local aromaticity. The results are supported by NICS and ACID calculations that indicate the global antiaromaticity of planar furan macrocycles, and by transient absorption measurements showing sharp absorption band for the trimer and only the internal conversion decay pathway. 相似文献
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Negativethermalexpansion (NTE)materialshavere ceivedconsiderableattentioninrecentyears ,1 6 especiallythecubicphasesZrW2 O8(c ZrW2 O8)andZrMo2 O8(c ZrMo2 O8) .TheseparticularmaterialsundergoisotropicNTEbehavioroverawidetemperaturerange ,0 3Kto10 5 0Kand 1378Kto 15 30KforZrW2 O81,2 and 0to 6 6 0KforZrMo2 O8,respectively .7c ZrMo2 O8possessesbenefi cialintrinsicproperties7 9overZrW2 O8,suchaslowerden sityandlowerphasetransitiontemperature ,butitstemper aturerangeforNTEisnarrowerth… 相似文献
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Jakub Ostapko Dr. Krzysztof Nawara Michał Kijak Dr. Joanna Buczyńska Dr. Barbara Leśniewska Dr. Mariusz Pietrzak Grażyna Orzanowska Prof. Jacek Waluk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17311-17320
Among seven possible nitrogen‐in constitutional isomers of porphyrin only one, porphycene, has been obtained so far in the free, unsubstituted form. Herein, the synthesis of another isomer, parent hemiporphycene ( HPc ), and its thorough structural, spectral, photophysical, electrochemical, and theoretical characterization are reported. Most of the properties of HPc are intermediate between those of porphyrin and porphycene, as evidenced by the values of inner‐cavity dimensions, orbital‐energy splittings, absorption coefficients, magnetic circular dichroism parameters, NH‐stretching frequencies, fluorescence quantum yields, tautomerization rates, and redox potentials. The largest differences arise with respect to tautomerism, due to the low symmetry of HPc and inequivalence of the four nitrogen atoms that define the inner cavity. Two trans tautomers are observed, separated in energy by about 1 kcal mol?1. Tautomerization from the higher‐ to the lower‐energy form is detected in the lowest‐excited singlet state and occurs at a rate that is about four orders of magnitude lower than that observed for porphycene. Hemiporphycene is a very good model for the investigation of inequivalent intramolecular H‐bonds present in one molecule; two such bonds in HPc reveal unusual characteristics, and the bond strength results from the interplay between the N ??? N distance and the N?H?N angle. 相似文献
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Polyterthiophene nanostructures consisting of periodic nanolines were prepared using the precursor polymer approach in conjunction with nanoimprint lithography. Precursor polynorbornylenes consisting of terthiophene side chains were prepared from their corresponding norbornylene monomers via ring opening metathesis polymerization. A copolymer consisting of terthiophene norbornylene and acetate norbornylene repeat units with a 50:50 composition exhibited a glass transition temperature of 52°C. Nanolines of percursor polynorbornylene were prepared by thermal nanoimprint lithography. The nanoimprinted precursor polymer was then converted to conjugated conductive polymer via chemical and electrochemical oxidation of the terthiophene side units. Nanoimprinted lines of conductive polyterthiophene exhibited high electrochromic contrast at 437 nm. 相似文献
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N.I. Maliavski O.V. Dushkin E.V. Tchekounova J.V. Markina G. Scarinci 《Journal of Sol-Gel Science and Technology》1997,8(1-3):571-575
Partially polycondensed γ-aminopropylsilanetriol, (APSTOL) was prepared by hydrolyzing γ-aminopropyltriethoxysilane at a hydrolysis
ratio 8.0. APSTOL contains up to 52% SiO2 and can be easily dissolved in water, forming clear solutions remaining stable practically at any pH value. The thermal evolution
of APSTOL when heating up to 1000°C was examined using TGA and FTIR techniques; the probable mechanism of the oxidative decomposition
of organic groups, with the formation of imino- and carboxyl-containing intermediates, has been discussed. Two magnesium silicates
of the enstatite and forsterite, compositions and two calcium silicates of the wollastonite and rankinite, compositions have
been prepared, using corresponding acetates and APSTOL as MIIO and SiO2 precursors. The crystallization, processes in these systems were studied by TGA and XRD techniques, after heat treatments
up to 1000°C. In all the systems, except rankinite, the parent silicates were found as the main crystalline phases. 相似文献
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Ju Li SHEN Hua Zhang LIU Xiao Nian LI Weng Feng HAN Yi Fan ZHENG 《中国化学快报》2005,16(10):1393-1396
The effect of the precursor composition of fused iron catalyst on the performance of Fischer-Tropsch synthesis was investigated. XRD, BET and CO2 adsorption experiments were carried out to provide better insight into the relationship therein. The results showed that the selectivity of C5+ hydrocarbon products was dependent on the mole ratio of Fe^2+/Fe^3+, which was represented by a hump-shaped curve. Catalysts with precursors containing Fe3O4 phase favored the magnetite spinal formation during F-T reaction, while Fe(1-x)O-based catalysts were more likely to favor the formation and growth of the iron carbide crystals. 相似文献