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1.
Dimitris Tomazos Gerardus Out James A. Heck Gary Johansson Virgil Perce Martin Möller 《Liquid crystals》2013,40(3):509-527
Abstract The phase behaviour of binary mixtures of self-assembled tapering molecules based on monoesters of oligooxyethylene glycol and 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoic acid, their corresponding polymethacrylates, and of 4′-methyl (benzo-15-crown-5)-3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoate within their hexagonal columnar mesophase (Φh) is described. The binary blends between molecular tapers co-assemble into a single supramolecular column resulting in isomorphism within their Φh mesophase over the entire range of composition. The binary blends between polymethacrylates containing tapered side groups co-assemble into a single Φh phase only when the columns of the parent polymers are of similar diameters. This results in binary mixtures which are isomorphic within the Φh mesophase over the entire composition range. When the diameters of the columns formed by the parent polymers are dissimilar, isomorphic mixtures are obtained only over a narrow range of composition. Binary mixtures between molecular tapers and macromolecular systems containing tapered side groups co-assemble into a single column to the extent that intercalation of the molecular taper, within the column formed by the macromolecular system containing tapered side groups, is permissible. In all systems increased intracolumnar interactions can be induced by complexation of CF3SO3Li by the oligooxyethylenic receptors leading to isomorphism in otherwise non-isomorphic mixtures. Ternary mixtures between molecular tapers with non-specific oligooxyethylenic receptors and specific crown ether receptors and CF3SO3 Na as the third component are non-isomorphic within their Φh phase due to preferential complexation of the alkali metal cation by the column of the crown ether containing the molecular taper. This results in two columns of dissimilar diameters, which are isomorphic in the Φh phase only within a limited range of composition. 相似文献
2.
Norikazu Nishiyama Yong-Rong Dong Tao Zheng Yasuyuki Egashira Korekazu Ueyama 《Journal of membrane science》2006,280(1-2):603-609
Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO2, O2, N2, CF4, n-C4H10 and i-C4H10, as well as binary mixtures of CH4/n-C4H10 and N2/CF4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH4/n-C4H10 mixtures and higher than 8100 for the N2/CF4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines. 相似文献
3.
采用分子动力学模拟方法, 研究了新型绝缘介质三氟甲基磺酰氟(CF3SO2F)的理化特性, 为高压电气设备应用CF3SO2F替代SF6气体提供了理论依据. 基于量子化学计算的分子结构、 内转动、 偶极矩和振动频率等优化设计了mPCFF力场模型, 计算了243~323 K温度范围内CF3SO2F的各种气-液相平衡性质(饱和蒸汽压、 密度、 热容、 蒸发焓和临界参数等)与关键输运特性(扩散系数、 介电常数、 黏度和热导率等)基础参数, 并考察了CF3SO2F与N2或CO2形成混合气体的理化特性. 通过对比SF6以及C4/CO2混合环保绝缘气体, 针对混合比、 液化温度、 扩散和热导等因素提出了CF3SO2F的电气设备应用建议. 相似文献
4.
Refaat I. Nessim 《Liquid crystals》2003,30(2):211-218
Five homologous series Ia-e, of the title compounds have been prepared and investigated for their mesophase behaviour in binary mixtures. Each series differs from the other by a substituent X, which changes between CH3O, CH3, Cl, CN, and NO2. The number of carbons in the terminal alkoxy group, within a homologous series, varies between 6, 8, 14, and 16. All possible binary combinations, made from any two components bearing an alkoxy group of the same chain length but two different substituents X, were prepared and similarly characterized for their phase behaviour. Transition temperatures of the mixtures were measured by differential scanning calorimetry and identified by polarizing optical microscopy. Phase diagrams were constructed for the various binary systems and discussed in terms of electronic effects. 相似文献
5.
Ralph Haist Hans-Georg Mack Alfred Waterfeld Gary L. Gard Heinz Oberhammer 《Journal of Molecular Structure》1996,380(3):213-222
The geometric structures and conformational properties of trifluoromethanesulfonic anhydride, (CF3SO2)2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF3SO2)2CF2 have been studied by gas electron diffraction (GED) and ab initio calculations (HF/3–21G*). The calculations predict for both systems two stable conformers with C2 symmetry and one with C1 symmetry. In both compounds structures with C2 symmetry and dihedral angles SOSC ≈ 100° ((CF3SO2)2O) and SCSC ≈ 150° ((CF3SO2)2CF2) are lowest in energy. According to the GED analyses the dominant conformer of (CF3SO2)2O possesses C2 symmetry with SOSC dihedral angles of 99.1(14)°. The presence of up to 30% of the two other conformers cannot be excluded; for (CF3SO2)2CF2 only one conformer with C2 symmetry and SCSC dihedral angles of 143(2)° is observed. A complete set of geometric parameters is given. 相似文献
6.
Binary mixtures formed from components of the five homologous series of the 4-(4-substituted phenylazo)phenyl-4-alkoxybenzoates Ia-e were prepared and their mesophase behaviour characterized. Transition temperatures of the mixtures prepared were measured by differential scanning calorimetry and identified by polarizing optical microscopy. Each binary combination was made from components bearing a terminal alkoxy group with the same number of carbon atoms (kept constant at n = 6, 8, 10, 12, 14 or 16), while the other substituent (X) was different—CH3O, CH3, Cl, NO2, or CN. Phase diagrams were constructed for the various systems in order to investigate the effect of the terminal substituent X, as well as of the alkoxy chain length, on the phase behaviour of mixed systems. 相似文献
7.
Ralph Haist Hans-Georg Mack Alfred Waterfeld Gary L. Gard Heinz Oberhammer 《Journal of Molecular Structure》1996,380(3):213-222
The geometric structures and conformational properties of trifluoromethanesulfonic anhydride, (CF3SO2)2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF3SO2)2CF2 have been studied by gas electron diffraction (GED) and ab initio calculations (HF/3–21G*). The calculations predict for both systems two stable conformers with C2 symmetry and one with C1 symmetry. In both compounds structures with C2 symmetry and dihedral angles SOSC ≈ 100° ((CF3SO2)2O) and SCSC≈ 150° ((CF3SO2)2CF2 are lowest in energy. According to the GED analyses the dominant conformer of (CF3SO2)2O2 possesses C2 symmetry with SOSC dihedral angles of 99.1(14)°. The presence of up to 30% of the two other conformers cannot be excluded; for (CF3SO2)2CF2 only one conformer with C2 symmetry and SCSC dihedral angles of 143(2)° is observed. A complete set of geometric parameters is given. 相似文献
8.
Richard D. Chambers Lee D. Proctor Gerardo Caporiccio 《Journal of fluorine chemistry》1995,70(2):241-247
Telomerisation reactions have been investigated for the alkenes 1,1-difluoroethene (5) and hexafluoropropene (3) with the telogens CF2Br2 (1), CF3CFBr2 (8) and CF3CBr3 (9), as a means of preparing telomers and co-telomers. The efficiency of chain transfer increases as 18<9. Surprisingly, co-telomerisations of 5 with 3 occurred more efficiently than the corresponding telomerisations with 5 alone. The effects of solvent are described. 相似文献
9.
The attempted preparation of bis(trifluoromethylsulphanyl)thioketene is described. Mono-and di-(trifluoromethylsulphanyl)-substituted orthothioesters may be prepared fromCH3C(SC2H5)3 and CF3SCl in the presence of anhydrous ZnCl2. The unstable compoundshave been isolated and characterized. The corresponding CF3Se and CF3SO2 derivativesare only formed as intermediates which decompose to ketene diethylmercaptal. Suchmono- and di-substituted products are obtained in good yield from H2C=C(SC2H5)2 andCF3ECl (E=S, Se). The reaction of H2C=C(SC2H5)2 with CF3SO2F gave only poor yieldsof (CF3SO2)nCH2−n=C(SC2H5)2 (n=1, 2) which were only capable of characterizationin etheral solution by spectral means. Attempts to prepare (CF3S)2C=C=S by refluxing(CF3S)2CHC(O)Cl, (CF3S)2CHC(O)OH or (CF3S)2C=C=O with P4S10 in toluene yieldedonly the cyclic dimer and the corresponding 1,3,4-trithiolan. 相似文献
10.
Chiu-Hui Yang Jo-Yu Tung Bing-Chuang Liau Bao-Tsan Ko Shanmugham Elango Jyh-Horung Chen Lian-Pin Hwang 《Polyhedron》2001,20(28):3257-3264
The crystal structure of bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato) thallium(III), Tl(N---Me---tpp)(CF3CO2)2 (2), was established and the coordination sphere around the Tl3+ ion is described as 4:3 tetragonal base–trigonal base piano stool seven-coordinate geometry in which the two cis CF3CO2 − groups occupy two apical sites. The plane of the three pyrrole nitrogen atoms [i.e. N(2), N(3) and N(4)] strongly bonded to Tl3+ is adopted as the reference plane 3N. The pyrrole N(1) ring bearing the methyl group [i.e. C(45)H3] is the most deviated one from the 3N plane making a dihedral angle of 23.3° whereas smaller angles of 9.9, 2.7 and 4.7° occur with pyrroles N(2), N(3), and N(4), respectively. Because of the larger size of the thallium(III) ion, Tl is considerably out of the 3N plane; its displacement of 1.02 Å is in the same direction as that of the two apical CF3CO2 − ligands. The intermolecular trifluoroacetate exchange process for 2 in CD2Cl2 solvent is examined through 19F and 13C NMR temperature-dependent measurements. In the slow-exchange region, the CF3 and carbonyl (CO) carbons of the CF3CO2 − groups in 2 are separately located at δ 114.3 [1J(C–F)=290 Hz, 3J(Tl–C)=411 Hz] and 155.1 [2J(C–F)=37 Hz, 2J(Tl–C)=204 Hz], respectively, at −106 °C. In the same slow-exchange region, the fluorine atoms of 2, Tl(N---Me---tpp)(CF3CO2)+ and the free CF3CO2 − are located at δ −73.76 [4J(Tl–F)=44 Hz], −73.30 [4J(Tl–F)=22 Hz], and −76.15 ppm at −97 °C, respectively. 相似文献
11.
Philip J. Bailey 《Journal of organometallic chemistry》1991,420(3):C21-C23
The reaction of the octahedral dianion [Ru6(CO)18]2− with trifluoromethanesulphonic (triflic) anhydride [(CF3SO2)2O] quantitatively yields the neutral carbido-cluster [Ru6C(CO)17] as a result of the cleavage of a coordinated carbonyl ligand. 相似文献
12.
Robert Toreki Richard R. Schrock William M. Davis 《Journal of organometallic chemistry》1996,520(1-2):69-78
Photolysis of compounds of the type [Re(CCMe2R)(OR′)2] (R = Me or Ph; OR′ = O′Bu, OCMe2(CF3), or OCMe(CF3)2) in benzene with a medium pressure mercury lamp yields compounds of the type [Re(OR′)2]2(μ-CCMe2R)2 in an intramolecular and irreversible manner. [Re(CCMe2R)(OR′)2]2 and [Re(OR′)2]2(μ-CCMe2R)2 (OR′ = O′Bu or OCMe2(CF3)2) both react with excess carbon monoxide in several solvents to afford the dimers [Re(OR′)2(CO)]2(μ-CCMe2R)2 quantitatively. An X-ray study of [Re(OtBu)2(CO)]2 (μ-CtBu)2 shows it to consist of two distorted trigonal bipyramids connected by two symmetrically bridging neopentylidyne ligands. The unbridged dimers of general formula [Re(CCMe2R)(OR′)2]2 do not react readily with simple substrates such as phosphines, olefins, or acetylenes, although [Re(CCMe2R)(OtBu)2]2 can be oxidized by iodine to yield Re(CCMe2R)(OtBu)2I2 in good yield. In contrast, {Re[OCMe(CF3)2]2}2(μ-CtBu)2 reacts with one equivalent of phenylacetylene to give a species in which one of the two bridging alkylidyne ligands is retained. 相似文献
13.
(C6H5)3MX2 (M = As, Sb; X = OCOCF3 and M = Sb, Bi; X = SO3F, SO3CF3) compounds prepared by the interaction of triphenylmetal(V) substrates with (CF3CO)2O, (CF3SO2)2O and (FSO2)2O have been characterized by molecular weight determination, elemental and spectroscopic (IR, 1H and 19F NMR, mass) analyses. 相似文献
14.
《Chemical physics》1995,200(3):309-318
Dynamics of electronic polarization in the vicinity of charge carriers in molecular crystals is for the first time investigated here in connection with the carrier transport and intramolecular vibronic polarization. According to standard picture it has been assumed that the electronic polarization relaxation time is extremely short, as estimated from the relation τc = τd1 ≈ h/Eexc, where Eexc is the energy of the first single exciton state. In the case of anthracene (Ac) crystals, the value of τe is about 2 × 10−16 s, i.e. by several orders of magnitude shorter than a typical hopping (residence) time of charge carriers τh = 10−14 -10−13 s. It is argued that typical time of full reconstruction of the electronic polarization after individual carrier hops equals, in the slow carrier regime, approximately to td2 ≈ h/ΔEexc is the width of the lowest singlet-exciton band. In Ac, this means td2 ≈ 0.73 × 10−14 s. Physical implications of this relatively high value of td2 in connection with carrier transport and molecular (vibronic) polarization are discussed. 相似文献
15.
Vivian Wing-Wah Yam Keith Man-Chung Wong Samuel Hung-Fai Chong Victor Chor-Yue Lau Sally Chan-Fung Lam Lingjun Zhang Kung-Kai Cheung 《Journal of organometallic chemistry》2003,670(1-2):205-220
A series of luminescent rhenium(I) monoynyl complexes, [Re(N---N)(CO)3(CC---R)] (N---N=bpy, tBu2bpy; R=C6H5, C6H4---Cl-4, C6H4---OCH3-4, C6H4---C8H17-4, C6H4---C6H5, C8H17, C4H3S, C4H2S---C4H3S, C5H4N), together with their homo- and hetero-metallic binuclear complexes, {Re(N---N)(CO)3(CC---C5H4N)[M]} (N---N=bpy, tBu2bpy; [M]=[Re{(CF3)2-bpy}(CO)3]ClO4, [Re(NO2-phen)(CO)3]ClO4, W(CO)5) have been synthesized and their electrochemical and photoluminescence behaviors determined. The structural characterization and electronic structures of selected complexes have also been studied. The luminescence origin of the rhenium(I) alkynyl complexes has been assigned as derived states of a [dπ(Re)→π*(N---N)] metal-to-ligand charge transfer (MLCT) origin mixed with a [π(CCR)→π*(N---N)] ligand-to-ligand charge transfer (LLCT) character. The assignments are further supported by extended Hückel molecular orbital (EHMO) calculations, which show that the LUMO mainly consists of π*(N---N) character while the HOMO is dominated by the antibonding character of the Re---CCR moiety resulted from the overlap of the dπ(Re) and π(CCR) orbitals. 相似文献
16.
Phase diagrams of multi-wall carbon nanotube (MWNT)/nematic liquid crystal (E7) and buckminsterfullerene (C60-I h)/nematic liquid crystal (E7) binary systems have been investigated by means of polarizing optical microscopy and differential scanning calorimetry. It was found that the isotropic-nematic phase transition temperature (T NI) of the liquid crystal component was enhanced by the incorporation of MWNT within a small composition gap. A chimney-type phase diagram can be identified in the MWNT/E7 mixture over a narrow range of ∼0.1-0.2% MWNT concentration. Upon substituting the nanotubes with isotropic fillers such as fullerene, the (C60-I h)/E7 blend showed no discernible change of T NI in the same concentration range of the chimney of the MWNT/E7 mixture, suggesting a significant contribution of anisotropy (or the aspect ratio) of the nanotubes to the entropy of the system containing liquid crystal molecules. This enhanced T NI phenomenon may be attributed to anisotropic alignment of liquid crystal molecules along the carbon nanotube bundles. 相似文献
17.
Oxolane was fluoroalkylated by its photoadditions under atmospheric pressure. Monofluoro-alkylations were carried out with hexafluoropropene (1) and perfluorovinyl ethers C3F7O-[CF(CF3)CF2O]n-CF = CF2 (24, n = 0–2) by direct photoexcitation of the olefins to give high yields of addition products 9–12 (81–94%). The reactions were completely regioselecti ve at the oxolane molecule and almost completely regioselective (93–99%) at the double bond of fluoro-olefins; no bis-fluoroalkylated oxolanes were detected. The completely selective introduction of a second fluoroalkyl into position 5 of the oxolane molecule was accomplished by acetone-sensitised photoaddition of 2fluoroalkylated oxolanes 9,10 to fluoro-olefins 1 and 2. Byproducts from reactions of the dimethylketyl radical which is formed in the initiation step were isolated and have given some evidence about the reaction mechanism that is discussed. 相似文献
18.
《Liquid crystals》2007,34(3):395-400
Poly(propyleneimine) [PPI-(NH2) n ] and poly(amidoamine) [PAMAM-(NH2) n ] dendrimers with n = 4, 8, 16, 32 and 64, have been functionalized with a semifluorinated carboxylic acid [CF3(CF2)7CH2CH2COOH] on the surface. The thermal and liquid crystal properties of the resulting ionic dendrimers have been studied by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). All dendrimers show a smectic A (SmA) mesophase, except that derived from the fifth generation of PPI, which displays a columnar mesophase. The mesomorphic behaviour of the dendrimers is attributed to the formation of ionic bonds and to the microsegregation of the dendritic branches and the fluorinated peripheral chains. 相似文献
19.
Ching-I Li Wen-Yann Yeh Shi-Ming Peng Gene-Hsiang Lee 《Journal of organometallic chemistry》2001,620(1-2):106-112
The perphenylmetallocene complexes (η5-C5Ph5)2W (1), [(η5-C5Ph5)2W]+I3− (1+I3), (η5-C5Ph5)2Mo (2) and [(η5-C5Ph5)2Mo]+I3− (2+I3) have been prepared. Hydrogenation of 1 in THF produces (η5-C5Ph5)2WH2 (4), while (η5-C5Ph5)2WHCl (3) is afforded in 1,2-dichloroethane solvent. Carbonylation of 1 produces (η5-C5Ph5)2W(CO) (5). Treatment of 1 with the strong acid CF3SO3H leads to the dicationic species [(η5-C5Ph5)2W]+2[CF3SO3]−2 (1+2Tf2) after crystallization. The structures of 2+I3 and 1+2Tf2 have been determined by an X-ray diffraction study. The magnetic susceptibility study indicates a 3E2g ground-state for 1 and 2, and a 4A2g ground-state for 1+ and 2+. 相似文献
20.
M. F tima C. Guedes da Silva Elsa M. P. R. P. Branco Yu Wang Jo o J. R. Fraú sto da Silva Armando J. L. Pombeiro Roberta Bertani Rino A. Michelin Mirto Mozzon Franco Benetollo Gabriella Bombieri 《Journal of organometallic chemistry》1995,490(1-2):89-99
Complexes trans-[PtX(L)(PPh3)2]A [1: X = CF3; A = BF4; L = NCNH2, NCNMe2, NCNEt2, or NCNC(NH2)2. 2: X = Cl; A = BPh4; L = NCNMe2 or NCNEt2] and cis-[PtCl(L)(PPh3)2][BPh4] [3: L = NCNH2 or NCNC(NH2)2], which appear to be the first cyanamide or cyanoguanidine complexes of platinum to be reported, have been prepared by treatment of trans-[PtBr(CF3)(PPh3)2] (in CH2Cl2/acetone and in the presence of Ag[BF4]) or of cis-[PtCl2(PPh3)2] (in THF and in the presence of Na[BPh4]), respectively, with the appropriate substrate. In KBr pellets or in solution 1 (L = NCNMe2 or NCNEt2) undergoes ready replacement of the organocyanamide (under the trans influence of CF3) by bromide to regenerate trans-(PtBr(CF3)(PPh3)2]. The X-ray structure of 1 (X = CF3, A = BF4, L = NCNEt2) is also reported, and shows the presence of two apical intramolecular contacts of the metal with two ortho-hydrogen atoms of the phosphines, whereas the amine N atom of the diethylcyanamide is trigonal planar in the linear NCN framework with a delocalized π system. 相似文献