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1.
A density functional theory investigation on a series of sandwich-type transition metal complexes [(CBO)n]2M (n=4–6; M=transition metals) with carbon boronyls (CBO)n as effective aromatic ligands has been presented in this work at B3LYP level. The ground-states of these complexes possess staggered Dnd symmetries, while the corresponding eclipsed Dnh structures exist as transition states with slightly higher energies (within 5.8 kJ/mol). Carbon boronyl complexes [(CBO)n]2M are confirmed to be much more stable than their boron carbonyl isomers [(BCO)n]2M, which, on the other hand, take eclipsed ground-states with Dnh symmetries. The carbon boronyl complexes [(BCO)n]2M proposed in this work parallelize the well-known sandwich-type hydrocarbon complexes [CnHn]2M in coordination chemistry with boronyl groups –BO isolobal to –H atoms in corresponding ligands.  相似文献   

2.
The preparation of liquid-crystalline 2,5-bis(4-alkyloxyphenyl) thiazolo [5,4-d] dithiazoles (ATTn), in which the alkyl group is CnH2n + 1 (where n = 1 to 10, 12), has been described. Mesomorphic properties and phase transitions as determined by polarizing hot stage microscopy and differential scanning calorimetry are discussed as a function of the number of carbon atoms in the alkyloxy chain. The exhibition of tilted smectic phases (smectic C and smectic I) by these compounds is an interesting feature since there is no significant central dipole moment transverse to these molecules.  相似文献   

3.
Some novel polystyrene-supported porphyrinatomanganese(III) in which alkyl group is bonded to the surface of polystyrene, PS-[Mn(HPTPP)Cl](CnH2n+1) (n=2, 6, 8, 18), have been synthesized. Their catalytic activities to hydroxylate cyclohexane in PS-[Mn(HPTPP)Cl](CnH2n+1)–O2–ascrobate system have been found to be higher compared with corresponding non-supported porphyrinatomanganese(III) and increase with the increase of the length of alkyl. These results are discussed in the point of view of metalloporphyrin microenvironment.  相似文献   

4.
Octakis(alkyloxyphenyl)-phthalocyanine derivatives ((CnOph)8PcH2 n = 8, 10 12 and 18), their corresponding copper (II) complexes ((CnOph)8PcCu, n = 10, 12 and 18) and octakis(2-ethylhexyl)-PcH2 have been synthesized and their mesomorphic properties characterized. (CnOph)8PcH2, (n = 12 and 18) exhibit hexagona disordered columnar mesophases whereas (CnOph)8PcCu (n = 12 and 18) yields a rectangular disordered columnar liquid crystal. An alkylphenyl-oxymethyl derivative, (C12phOCH2)8PcH2, was synthesized to determine the influence of the connecting link between the side chains and the phthalocyanine macrocycle on the mesomorphic properties.  相似文献   

5.
Di-q-polyhexes are polygonal systems consisting of two q-gons each and otherwise only hexagons. General formulations are reported for the CnHs chemical formulae of such systems for q = 4, 5, 6. The case of q = 4 (terphenylenoids) is treated systematically for the first time. Constant-isomer series of CnHs formulae, which have been known to exist for benzenoids (q = 6) and indacenoids (q = 5), are reported here for terphenylenoids.  相似文献   

6.
《Liquid crystals》2000,27(8):1103-1112
Two fused-ring structures, 6-decyloxy-2-naphthoic acid C10ONA (3) and 6-dodecyloxyisoquinoline IS (8), were synthesized and utilized as proton donor and acceptor moieties to construct a series of simple mesogenic supramolecules. The other complementary hydrogen-bonded (H-bonded) moieties are benzoic acids, thiophenecarboxylic acid and pyridines containing different alkyl chain lengths connected by ether and ester linkages, i.e. 4-alkoxybenzoic acid CnOBA (1), terephthalic acid monoalkyl ester CnCOOBA (2), 2,5-thiophenedicarboxylic acid monodecyl ester C10COOTHA (4), 4-alkoxypyridine CnOP (6) and isonicotinic acid alkyl ester CnCOOP (7). Several series of simple mesogenic supramolecular dimers were constructed from 1:1 molar ratios of proton donors (CnOBA, CnCOOBA, C10ONA and C10COOTHA) and proton acceptors (IS, CnOP and CnCOOP), though the proton acceptor CnCOOP induced phase separation in all complexes. In order to investigate their fused-ring and linking group effects on the mesogenic properties of the H-bonded complexes, analogous simple supramolecular structures are compared. Supramolecular architecture and the distinct mesomorphism of these simple H-bonded liquid crystalline materials were confirmed by polarizing optical microscopy, DSC and powder X-ray diffraction experiments.  相似文献   

7.
8.
A homologous series of double-chain non-ionic surfactants with the general formula (Cn)2 GEmM, where Cn denotes an alkyl chain, G a triglyceryl, and EmM an oligo-oxyethylene mono-methyl ether are synthesized withn=6–8 andm=6, 8, 10. The branched hydrophobic part of the surfactants introduces a large cross-section of the lipophilic surfactant moiety that is directly reflected in the shape of the micelles and the LC phase behavior in aqueous solution. The phase behavior of these V-amphiphiles is investigated with polarizing microscopy and x-ray diffraction and reveals that the branched lipophilic part strongly stabilizes the lamellar mesophase. This is in agreement with established packing models.  相似文献   

9.
Broad peaks are obtained when purely aqueous micellar phases are used in micellar liquid chromatography (MLC). The causes of reduced efficiency in MLC are investigated. Slow solute mass-transfer kinetics between micelles, the aqueous phase and the surfactant covered stationary phase are the origins of the efficiency loss. Knox plots show that the reduced efficiency comes from A term increase and, for lipophilic solutes, A and C terms increases. Surfactant adsorption reduces the pore volume and surface area of the stationary phase changing the flow anisotropy (A term). The surfactant adsorbed layer slows down the mass transfer (C term). Three ways for efficiency loss remediation are known: flow-rate reduction, temperature increase and alcohol addition. Alcohols are known to change the micelle structure and to increase the kinetics of micelle formation-destruction. It is shown that the ratio of the alcohol chain length to surfactant alkyl chain length, Cn, OH/Cnm surf, should be equal or higher than 1/3 to produce the best efficiency enhancements in MLC. Also, the volume of alcohol to be added is not absolute but relative to the surfactant concentration. The alcohol to surfactant concentration ratio should be kept constant. Temperature increases and especially alcohol additions reduce the retention factors. Thermodynamic and kinetics of the micellar exchanges in MLC cannot be dissociated.  相似文献   

10.
The geometries for the planar T1 states of linear polyenes CnHn+2 (n=8, 10, 12, 14, 16, 18, 20, and 22) were optimized by ab initio SCI calculations. It was found that the bond alternation which existed in the S0 state disappears only in the central region of the polyene chain. This is quite similar to the ‘triplet-excited region’ which was observed in PPP SDCI calculations for decapentaene (n=10), tetradecaheptaene (n=14), octadecanonaene (n=18), and docosaundecaene (n=22) (M. Kuki, Y. Koyama, N. Nagae, J. Phys. Chem. 95 (1991) 7171). However, CASSCF calculations performed for octatetraene (n=8) gave considerably different geometries from the SCI geometries. The reason for this is discussed and we conclude that the appearance of the ‘triplet-excited region’ in SCI and SDCI calculations is artifactual.  相似文献   

11.
Dialkyl disulfide-linked naphthoquinone, (NQ-Cn-S)2, and anthraquinone, (AQ-Cn-S)2, derivatives with different spacer alkyl chains (Cn: n = 2, 6, 12) were synthesized and these quinone derivatives were self-assembled on a gold electrode. The formation of self-assembled monolayers (SAMs) of these derivatives on a gold electrode was confirmed by infrared reflection-absorption spectroscopy (IR-RAS). Electron transfer between the derivatives and the gold electrode was studied by cyclic voltammetry. On the cyclic voltammogram a reversible redox reaction between quinone (Q) and hydroquinone (QH2) was clearly observed under an aqueous condition. The formal potentials for NQ and AQ derivatives were −0.48 and −0.58 V, respectively, that did not depend on the spacer length. The oxidation and reduction peak currents were strongly dependent on the spacer alkyl chain length. The redox behavior of quinone derivatives depended on the pH condition of the buffer solution. The pH dependence was in agreement with a theoretical value of E1/2 (mV) = E′ − 59pH for 2H+/2e process in the pH range 3–11. In the range higher than pH 11, the value was estimated with E1/2 (mV) = E′ − 30pH , which may correspond to H+/2e process. The tunneling barrier coefficients (β) for NQ and AQ SAMs were determined to be 0.12 and 0.73 per methylene group (CH2), respectively. Comparison of the structures and the alkyl chain length of quinones derivatives on these electron transfers on the electrode is made.  相似文献   

12.
The synthesis and structural characterization of tetra(1H, 1H, 2H, 2H-polyfluoroalkyl)silaneswith the same or different chain lengths CnF2n+1 linked to Si (1n6) is reported.

When the synthesis was effected from chlorosilanes and fluorinated organomagnesiumor organolithium reagents, the trialkylsilanes were obtained. The last fluorinated chainwas introduced either via a fluoroalkyllithium reagent or by hydrosilylation of thetrialkylsilanes.

Some properties and characterization by 1H, 19F and 29Si NMR spectroscopy of the1H, 1H, 2H, 2H-polyfluoroalkylsilanes are described.  相似文献   


13.
A series of N-[4'-(dodecyloxy)resorcylidene]-4-(RO*)-anilines (HLn n = 1, R*O = (-)-cis-myrtanyl; n = 2, R*O = (-)-menthyl; n = 3, R*O = S-(-)-β-citronellyl; n = 4, R*O = R-(-)-2-octyl) has been synthesized and the mesomorphic properties investigated. These ligands are able to chelate a metal atom; accordingly three different series of palladium complexes, [(Ln)Pd(Ln)], [(Ln)Pd(Azoxy-6)] and [(L3)Pd(Ph-Pyn)] (where Azoxy-6 and PhPyn are cyclopalladated 4,4'-dihexyloxyazoxybenzene and 5-substituted-2-(4-substituted-phenyl)pyrimidine, respectively) have been prepared. The mesogenic HL3 and HL4 ligands exhibit a S*C phase, retained in [(L3)Pd(L3)], which changes to a cholesteric phase in [(L4)Pd(L4)] and becomes the more ordered S*H phase in the [(Ln)Pd(Azoxy-6)] (n = 3,4) derivatives. In contrast, in the [(L3)Pd(Ph-Pyn)] compounds the mesomorphic phase is a SA phase.  相似文献   

14.
A new optically active (R)-3-ethylmercapto-2-methylpropionic acid has been synthesized using D(-)—2,10-camphorsultam as a chiral auxiliary. The optical purity of the acid obtained was greater than 98 per cent. Its derivatives, (R)-4-(3-ethylmercapto-2-methylpropionyl)phenyl 4'-alkoxybiphenyl-4-carboxylates (EMMPPmBC; m = 7-16), have been prepared for the investigation of liquid crystalline properties as a function of peripheral alkyl chain length. Optical studies showed that all members exhibited an antiferroelectric S*cA phase. The results also indicate that a lengthened alkyl chain length is favoured for ScA* phase formation.  相似文献   

15.
Previous structural investigations of mesogenic organosilicon compounds (1, 3-dihydroxytetraalkyldisiloxanes, [R2(OH)Si]2O, R = CnH2n+1) which form thermotropic phases are outlined. The crystal and molecular structure determination of a non-mesogenic member of this series [Me2(OH)Si]2O is described. It is inferred that the mesophases formed by this family of compounds belong to a new structural type with columnar stacks of the molecules laced together with hydrogen bonds.  相似文献   

16.
通过引进新的溶液制备方法,以光散射、流变、电镜等方法研究了烷烃链长度不对称的阴/阳离子表面活性剂等摩尔混合体系,其中阳离子为二十二烷基三甲基溴化铵(C22TABr),阴离子是烷基羧酸钠(Cn-1COONa, n = 4, 6, 8, 10, 12, 14, 16).结果表明,烷烃链长度高度不对称时(C22/n4)生成了球状胶束,随着降低不对称度,聚集体向棒状、蠕虫状直至囊泡转变.在构成囊泡的体系中,随着降低链长不对称度,聚集体尺寸明显增大.机理分析表明,阴/阳离子对的几何形状决定了聚集体的形貌以及它们的转变.  相似文献   

17.
提出了关于离子液体的新理论——离子交换跃迁模型,通过理论推导得出1:1型离子液体的Walden乘积仅取决于离子对和离子簇直径的统计平均值,即离子液体的阴阳离子结构不同,Walden乘积不同。为了验证模型的正确性,本文合成8种N-烷基-吡啶二氰胺类和N-烷基-咪唑丝氨酸类离子液体,利用上述离子液体的电导率和动力粘度的实验值及文献数据,计算了33种离子液体的Walden乘积。通过比较发现,不同离子液体的Walden乘积不同,即对于离子液体来说,Walden乘积是它的特征物理量。  相似文献   

18.
A homologous series of chiral materials, (R)-2-pentyl (S)-2-(6-(4-(4'-alkoxyphenyl)benzoyloxy)-2-naphthyl)propionates (R,S)PmPBNP (m = 7-14), derived from a naphthalene ring as part of the core structure in conjunction with a chiral tail containing two stereocentres has been synthesized for the investigation. The twist grain boundary smectic A (TGBA) and smectic C (TGB*C) phases were characterized by the microscopic textures of compounds packed in two untreated glass slides, Cano wedge cell, or homogeneously aligned cell. It was found that the occurrence of these phases depend remarkably on the nature of alkyl chain length m; in the case of shorter alkyl chain length (m = 7-10), the TGBA phase behaves as a metastable-like phase mediated between N and SA phases in a short temperature range, whereas in the longer chain length (m' 11-14), both the TGBA and TGBC phases become thermodynamically stable phases with a wide temperature range. Consequently, this series of chiral materials resulted in two different mesophase sequences: N-TGBA-SA-SCand N-TGBA-TGBC. A kind of parquet texture displaying two types of domain with different relative directions of the smectic layer normal was found in the S phase from the materials (m = 9-14) packed in 2 μm homogeneously aligned cells and cooled down from the isotropic liquid without applying an electric field. The magnitudes of spontaneous polarization (Ps) in the SC and TGBC phases showed that the Ps values are nearly the same for all compounds at the same temperature below the Curie point. Dielectric measurements revealed no significant occurrence of soft mode switching in the TGBA phase.  相似文献   

19.
Difluorinated higher fullerenes have been studied by Knudsen cell mass spectrometry. Thermal negative ions CnF2 (n=60, 70, 72, 74, 76 and 78) were produced inside the effusion cell as well as the neutral molecules C60F2 and C70F2. From the equilibrium constants for the electron exchange reactions between difluorinated fullerenes and their parents electron affinity values were derived for C60F2 (2.74 eV) and C70F2 (2.80 eV).  相似文献   

20.
A structural study of odd-numbered n-alkane (Cn) binary mixtures (C21 : C23) was carried out on powder samples using a Guinier-de Wolff camera with increasing concentration of n-C23 at 293 K.

Despite the reports in the literature, these molecular alloys do not form an orthorhombic continuous homogeneous solid solution to C21 from C23 at “low temperature”. Instead, as already observed in two even-numbered Cn systems, X-ray diffraction results show the existence of seven solid solutions as the molar concentration of C23 increases: four terminal solid solutions, denoted β0(C210(C23), isostructural with the “low temperature” phase of pure C21 and C23 (Pbcm), β′0(C21) and β′0(C23), identical to the phase β′0 which appears in pure C23 above the δ transition, and three orthorhombic intermediate solid solutions, designated β″1, β′1 and β″2.

On the basis of powder X-ray photographs, the phases β″1 and β″2 (C21 : C23) are indistinguishable, and they are isostructural with the intermediate solid solution β″ of the even-numbered Cn binary systems (C22 : C24) and (C24 : C26). The phase β′1(C21 : C23) is also isostructural with the two indistinguishable intermediate solid solutions β′1 and β′2 of the molecular alloys (C22 : C24) and (24 : C26).

From this study and our other laboratory results, the sequences of appearance of the solid solutions and the structural identities between these phases are established at “low temperature” for all the binary molecular alloys of consecutive Cn (odd-odd, even-even or odd-even: 19 < n < 27) when increasing the solute concentration.  相似文献   


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