Fused-ring and linking group effects of proton donors and acceptors on simple H-bonded liquid crystals

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 C _n OBA (1), terephthalic acid monoalkyl ester C _n COOBA (2), 2,5-thiophenedicarboxylic acid monodecyl ester C₁₀COOTHA (4), 4-alkoxypyridine C _n OP (6) and isonicotinic acid alkyl ester C _n COOP (7). Several series of simple mesogenic supramolecular dimers were constructed from 1:1 molar ratios of proton donors (C _n OBA, C _n COOBA, C₁₀ONA and C₁₀COOTHA) and proton acceptors (IS, C _n OP and C _n COOP), though the proton acceptor C _n COOP 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.     

Supramolecular liquid crystals containing isoquinoline hydrogen-bonded acceptors

6-Dodecyloxyisoquinoline IS ( 1 ) has been synthesized and utilized as a proton acceptor to generate a series of novel mesogenic supramolecules. Two mesogenic supramolecular dimers IS-OBA and IS-COOBA have been constructed from a 1:1 molar ratio of IS complexed either with 4-decyloxybenzoic acid OBA ( 2 ) or with 4-decyloxycarbonylbenzoic acid COOBA ( 3 ). A kinked mesogenic supramolecular trimer, i.e. a double H-bonded complex (IS)-THDA, has been constructed from a 2:1 molar ratio of IS complexed with 2,5-thiophenedicarboxylic acid THDA ( 4 ). The mesogenic properties of the H-bonded complex (IS2)-THDA are compared with those of previously reported H-bonded complexes (C12PS)-THDA and (C12PP2)-THDA consisting of a 2:1 molar ratio of trans -4-dodecyloxy-4-stilbazole C12PS 2 ( 5 ) or 4-dodecyloxypyridine C12PP2 (6 ) with THDA. Significantly, the first isoquinoline-based supramolecular liquid crystals have been built, and their mesogenic properties have been introduced or modified by fused- N -heterocyclic rings.     

Discotic liquid crystals of transition metal complexes X. Phthalocyanine derivatives substituted with n-alkyloxyphenyl side chains

Octakis(alkyloxyphenyl)-phthalocyanine derivatives ((C_nOph)₈PcH₂ n = 8, 10 12 and 18), their corresponding copper (II) complexes ((C_nOph)₈PcCu, n = 10, 12 and 18) and octakis(2-ethylhexyl)-PcH₂ have been synthesized and their mesomorphic properties characterized. (C_nOph)₈PcH₂, (n = 12 and 18) exhibit hexagona disordered columnar mesophases whereas (C_nOph)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.     

咪唑基表面活性离子液体在气/液界面的扩张粘弹性

合成了两种咪唑基表面活性离子液体,通过界面膨胀流变法研究了其在气/液界面的聚集行为,考察了咪唑基表面活性离子液体浓度、无机盐和温度对聚集行为的影响。研究发现,咪唑基表面活性离子液体在吸附过程中吸附控制占主导作用,而弛豫过程不是单一指数函数;加入无机盐或升高温度可以提高咪唑基表面活性离子液体的表面活性、增强其在界面的吸附能力、降低表面张力。扩张流变结果显示扩张模量、弹性模量和粘性模量随震荡频率增加而增加;随表面活性离子液体浓度增大,扩张模量先增大后减小。扩张模量随温度升高或无机盐(NaBr或CaBr₂)的加入而降低。表面活性离子液在气/液界面形成的吸附膜以弹性模量为主,而且C₁₄mimBr的界面膜弹性模量大于C₁₂mimBr的界面膜弹性模量。     

Synthesis and optical behaviour of hydrogen-bonded liquid crystals based on a chiral pyridine derivative

Three series of cholesteryl-containing supramolecular hydrogen-bonded (H-bonded) liquid crystal (LC) complexes with different number of fluoro-substituent were synthesised and characterised. Cholesteryl isonicotinate as proton acceptor and 4-n-alkoxybenzoic acids with or without fluoro-substituent as proton donor had been mixed in tetrahydrofuran to obtain H-bonded LC complexes. The effect of lateral substitution and the length of terminal chain in the H-bonded precursors on the formation of the supramolecular complexes had been examined. It was found that the introduction of fluoro substituent on the induced mesogens could widen the molecular width and thus reduce the molecular aspect ratio of the complexes, therefore it could lead to compress the formation of the LCs. However, the fluoro substituent played a positive role in enhancing the intermolecular interactions and stabilising the H-bond structure of the complexes. The influence of terminal length on the mesogenic behaviours is also discussed. On increasing the spacer length, the clear point and the thermal range of induced mesophase-like cholesteric phase decreased, and an induced chiral smectic phase began to appear in some complexes with long terminal tails.     

Structural evolutions of the n-heneicosane and n-tricosane molecular alloys at 293 K

A structural study of odd-numbered n-alkane (C_n) 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 C_n 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(C₂₁)β₀(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 C_n 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 C_n (odd-odd, even-even or odd-even: 19 < n < 27) when increasing the solute concentration.     

The catalysis of some novel polystyrene-supported porphyrinatomanganese(III) in hydroxylation of cyclohexane with molecular oxygen

Some novel polystyrene-supported porphyrinatomanganese(III) in which alkyl group is bonded to the surface of polystyrene, PS-[Mn(HPTPP)Cl](C_nH_2n+1) (n=2, 6, 8, 18), have been synthesized. Their catalytic activities to hydroxylate cyclohexane in PS-[Mn(HPTPP)Cl](C_nH_2n+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.     

Rare earth alkyl and hydride complexes bearing silylene-linked cyclopentadienyl-phosphido ligands. Synthesis, structures, and catalysis in olefin hydrosilylation and ethylene polymerization

A series of silylene-linked cyclopentadienyl-phosphido rare earth alkyl and hydride complexes of type Me₂Si(C₅Me₄)(PR′)LnR (Ln=Y, Yb, Lu; R′=Ph, Cy, C₆H₂^tBu₃-2,4,6; R=CH₂SiMe₃, H) have been synthesized and structurally characterized, and their activity in ethylene polymerization and olefin hydrosilylation has been studied. These complexes represent the first examples of rare earth alkyl and hydride complexes bearing cyclopentadienyl-phosphido ligands, which are in sharp contrast both structurally and chemically with the analogous cyclopentadienyl-amido and metallocene complexes.     

Observation of difluorinated higher fullerene anions by Knudsen cell mass spectrometry and determination of electron affinities of C60F2 and C70F2

Difluorinated higher fullerenes have been studied by Knudsen cell mass spectrometry. Thermal negative ions C_nF₂⁻ (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).     

Branched non-ionic oligo-oxyethylene Y-amphiphiles Effect of molecular geometry on the micellar shape 1

A homologous series of branched, non-ionic surfactants with the general formula C_nG(E_mM)₂, where C_n denotes an alkyl chain, G = glycerol and E_mM = oligo-oxyethylene mono-methyl ether, has been prepared from alkyl bromides (n = 10-16) and several monodisperse 1,3-di(methoxyoligo-oxyethylene) ethers of glycerol (m = 3-5). The branched hydrophilic chain is introduced to modify the interfacial area compared to corresponding linear oligo-oxyethylene surfactants (I-amphiphiles) without essentially changing the hydrophilic-lipophilic balance. The phase behaviour of these Y-surfactants in aqueous solution reveals that according to established packing models the branched hydrophilic group strongly stabilizes the cubic and hexagonal mesophases, while a lamellar phase is not observed.     

Electrical impedance spectroscopy characterisation of supported ionic liquid membranes

Supported liquid membranes (SLMs), prepared by immobilising the room temperature ionic liquids (RTILs) [C_nMIM]PF₆ (n = 4 and 8) and [C₁₀MIM]BF₄ in a polyvinylidene (PVDF) supporting membrane, were prepared and characterised by electrochemical impedance spectroscopy (IS). This non-invasive technique allows the determination of the electrical properties of a given sample, such as the electrical resistance and capacitance under working conditions, i.e., in contact with saline solutions.

Bearing in mind that the water content of the ionic liquids can drastically affect their physicochemical properties, impedance measurements of the SLMs, placed between two aqueous solutions, were carried out at regular time intervals, in order to assess the impact of the presence of water inside the RTILs on the electrical properties of supported ionic liquid membranes. The electrical resistance of the SLMs and its variation during long-term operation was also used as a physical parameter to identify the presence/loss of ionic liquid from the pores of the support. Additionally, the comparison of the IS results obtained for the SLMs with those obtained for the supporting membrane was carried out, in order to gather information about electrical changes associated with the presence of ionic liquid in the pores.     

Mesogenic behaviour of (4-alkoxybenzylideneamino)bromobenzene, (4-alkoxybenzylideneamino)benzenethiols, and thiolatonickel complexes of the thiols

The synthesis, characterization and mesogenic properties of Schiff base compounds arising from the reaction of 4-alkoxybenzaldehydes with 4-aminothiophenol or 4-bromoaniline are described. Whereas the Schiff base thiol with two benzene rings in the molecule, HSC₆H₄NC(H)C₆H₄OC₁₆H₃₃ (2), is non-mesogenic, the bromo analogue, BrC₆H₄NC(H)C₆H₄OC₁₆H₃₃ (3), is mesogenic. The introduction of a third benzene ring into the molecular architecture of 2 and 3 produced thiol- and bromo-Schiff base compounds, HSC₆H₄NC(H)C₆H₄OC(O)C₆H₄OC₁₆H₃₃ and BrC₆H₄NC(H)C₆H₄OC(O)C₆H₄OC₁₆H₃₃, respectively, that are both mesogenic. The thiol compounds react with nickelocene to form [(η ⁵-C₅H₅)Ni(μ ₂-SC₆H₄NC(H)C₆H₄OC₁₆H₃₃)]₂ and [(η ⁵-C₅H₅)Ni(μ ₂-SC₆H₄NC(H)C₆H₄OC(O)-C₆H₄OC₁₆H₃₃)]₂, but the nickel complexes are not mesogenic.     

Mesogenic Unsymmetric dimers containing cholesteryl ester and tolane moieties

Among unsymmetric oligomesogens, chiral dimers formed by connecting a cholesteryl ester fragment with various aromatic mesogenic cores through a polymethylene spacer have been attracting much attention due to their remarkable thermal behaviour. In particular, dimers containing a diphenylacetylene segment having an alkoxy chain have shown interesting mesomorphic behaviour. In view of this a new series of unsymmetric dimers consisting of a diphenylacetylene moiety having an alkyl chain and a cholesteryl ester unit joined through a paraffinic spacer have been synthesized and their liquid crystalline properties characterized. The lengths of the central methylene spacer (C₃, C₄, C₅ and C₇) as well as that of the alkyl chain (n-butyl, n-pentyl, n-hexyl and n-heptyl) have been varied to establish structure-property relationships. These investigations have revealed that all the dimers exhibit smectic A, twist grain boundary and chiral neamtic (N*) phases with the exception of one of the dimers for which only the N* phase was observed. Some differences in the mesomorphic properties of the unsymmetric dimers containing odd or even parity methylene spacers have been observed. The majority of dimers having an even (C₄) parity paraffinic spacer show a blue phase while the dimers with odd (C₃, C₅ and C₇) parity spacers exhibit the chiral smectic (SmC*) phase. In some cases, the SmC* phase exists well below (-60°C) and above room temperature.     

Hydrogen bond-induced ferroelectric liquid crystals

Hydrogen-bonded dimers of 4-alkoxy-4'-stilbazole homologues (C_nOSB, proton acceptors) and the mono-(2-methylbutyl)ester of terephthalic acid (MBTA, proton donor) behaved like conventional thermotropic mesogens. For chiral MBTA mixtures, chiral nematic and blue phases were observed with n = 1 and 2, and chiral smectic C phases were observed with n ≥ 5. Achiral phases were observed for mixtures with racemic MBTA as proton donor. Transition temperatures and enthalpies are similar for the chiral and achiral systems.     

Supramolecular hydrogen-bonded liquid–crystalline polymer complexes. Design of side-chain polymers and a host–guest system by noncovalent interaction

Supramolecular liquid–crystalline polymeric complexes based on a backbone that contains vinyl pyridine units and azobenzene or biphenyl derivatives that posses alkyl chains terminated by carboxylic acid have been obtained by the formation of intermolecular hydrogen bonds between the carboxylic acid and the pyridyl moieties. The polymeric complexes behave as side-chain liquid–crystalline polymers and exhibit smectic phases. A new type of H-bonded host-guest liquid–crystalline system is also reported. The liquid–crystalline host copolymers contain both mesogenic acrylate and 4-vinylpyridine units. The guest molecule is an azobenzene that has a carboxylic acid moiety at one of its extremities. The H-bonded polymeric host–guest complexes exhibit nematic phases. Sequential UV and visible light irradiation of the polymeric complex causes reversible photochemically induced phase transitions. The isothermal nematic–isotropic and isotropic–nematic transitions result from the trans-cis and cis-trans photoisomerization of the guest azobenzene in the host–guest system. © 1996 John Wiley & Sons, Inc.     

杂多酸/离子液体杂化材料催化苯的高选择性羟基化

制备了V取代的磷钼酸H_3+xPMo_12-xV_xO₄₀（x=0,1,2）及1-丁基-3-甲基咪唑溴盐离子液体（[C₄mim]Br）,并采用离子交换的方法制备了系列杂化材料（[C₄mim]3+xPMo_12-xV_xO₄₀,x=0,1,2）;采用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、紫外-可见漫反射光谱（UV-Vis DRS）对所制备样品进行了表征;以H₂O₂为氧化剂,考察了所得样品催化苯羟基化制苯酚的活性。结果表明,和相应的离子液体及杂多酸相比,杂化材料的催化活性得到了很大的提高,尤其是催化剂[C₄mim]₅PMo₁₀V₂O₄₀,在优化后的条件下,苯的转化率可达到21%,苯酚的选择性在99%以上。而且,该催化剂具有很好的可重复使用性,连续使用五次后,苯的转化率和苯酚的选择性没有明显降低。     

A new structural type of liquid crystal Crystal structures and thermotropic mesophases of dihydroxytetraalkyldisiloxanes: Columnar phases with hydrogen bonded assemblies

Previous structural investigations of mesogenic organosilicon compounds (1, 3-dihydroxytetraalkyldisiloxanes, [R₂(OH)Si]₂O, R = C_nH_2n+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.     

Sandwich-type transition metal complexes [(CBO)n]2M with carbon boronyl ligands (CBO)n (n=4–6)

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 D_nd symmetries, while the corresponding eclipsed D_nh 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 D_nh symmetries. The carbon boronyl complexes [(BCO)_n]₂M proposed in this work parallelize the well-known sandwich-type hydrocarbon complexes [C_nH_n]₂M in coordination chemistry with boronyl groups –BO isolobal to –H atoms in corresponding ligands.     

Synthesis of titanium(IV) complexes that contain the Bis(silylamide) ligand of the type [1,8-C10H6(NR)2], and alkene polymerization catalyzed by [1,8-C10H6(NR)2]TiCl2-cocatalyst system

[1,8-C₁₀H₆(NR)₂]TiCl₂ (3; R=SiMe₃, SiⁱBuMe₂, SiⁱPr₃) complexes have been prepared from dilithio salts [1,8-C₁₀H₆(NR)₂]Li₂ (2) and TiCl₄ in diethyl ether in moderate yields (60–63%). These complexes showed significant catalytic activities for ethylene polymerization and for ethylene/1-hexene copolymerization in the presence of methylaluminoxane (MAO), methyl isobutyl aluminoxane (MMAO), AlⁱBu₃– or AlEt₃–Ph₃CB(C₆F₅)₄ as a cocatalyst. The catalytic activities performed in heptane (cocatalyst MMAO) were higher than those carried out in toluene (cocatalyst MAO): 709 kg-PE/mol-Ti·h could be attained for ethylene polymerization by using [1,8-C₁₀H₆(NSiⁱBuMe₂)₂]TiCl₂–MMAO catalyst system.     

基于超分子离子晶体的湿度传感构效关系研究

相对湿度是许多领域的关键参数,环境湿度与人们的生活密切相关,因此对湿度进行测量和控制是各个领域中值得关注的问题之一. 在前期的研究中,作者制备了一种新型的超分子离子材料（SIM）,它是由基于咪唑的双阳离子（如1,10-双（3-甲基咪唑-1-基）癸烷,C₁₀(mim)₂）和电活性二阴离子（如2,2'-连氮基-双（3-乙基苯并噻唑啉-6-磺酸）,ABTS）组成的,发现其对湿度具有敏感且快速的响应. 在此基础上,本文制备了6种不同碳链（C₄,C₆,C₈,C₁₀,C₁₂,C₁₄）的咪唑基化合物,发现其中3种（C₁₀,C₁₂,C₁₄）可与ABTS形成水稳定的SIM. 循环伏安法、计时电流法以及石英晶体微量天平表征了这些超分子离子材料的湿度传感性能,发现基于C12的SIM具有最佳的湿度传感性能. 同时,SEM结果显示随着碳链的增加,离子材料的厚度变薄并且形态变得不规则. 因此,作者认为疏水作用和材料比表面积均会影响湿度传感的灵敏度. 本研究为发展新的湿度响应的离子传感材料奠定了基础.