On the thermodynamics of aggregation toward phosphorescent metallomesogens:From electronic tuning to supramolecular design

Two series with three Pt(II)complexes each(PtLPh-n,PtLFpy-n)bearing asymmet-ric tetradentate ligands as dianionic luminophores with variable alkyl chain lengths were synthesized.Hence,each ligand series is distinguished by one of its cyclomet-allating rings(phenyl vs.2,6-difluoropyrid-3-yl).Steady-state and time-resolved photoluminescence spectroscopic studies in diluted solutions at room temperature and in glassy matrices at 77 K show that the emissive state is mainly centered on the invariantly electron-rich cyclometalated side while the second ring regulates the admixture of ligand-centered and metal-to-ligand charge-transfer character.Hence,the radiative rates can be controlled,as indicated by quantum-mechanical calcula-tions,which also explain the temperature-dependent trend in the phosphorescence rate constants.Studies in condensed phases(single-crystal X-ray diffractometry,polarized optical microscopy,differential scanning calorimetry,steady-state and time-resolved photoluminescence micro(spectro)scopy)showed the development of a smectic A mesophase for thefluorinated species bearing the two longest alkyl chains.Nuclear magnetic resonance-based studies on the thermodynamics of aggre-gation in solution confirm the marked enthalpic stabilization of aggregates mediated by the polar 2,6-difluoropyrid-3-yl moiety(and to a lesser extent by dispersive forces between the alkyl chains).On the other hand,the negative entropy of aggregation is dominated by the restriction of degrees of freedom involving the peripheral alkyl moieties upon stacking,which becomes increasingly relevant for longer chains.All these factors control coupling,a crucial interaction for the design of Pt⋅⋅⋅Ptphotofunctional mesogens based on Pt(II)complexes.

Water-soluble hollow nanocrystals from self-assembly of AIEEactive Pt(II)metallomesogens

Luminescent hollow micro-and nanocrystals have been successfully obtained taking advantage of the self-assembly behavior and the aggregation-induced emission enhancement properties of several bispyrazolate Pt(II)metallomesogens decorated with four terminal alkyl chains.Oil-in-water droplets have been used to confine the Pt(II)compounds and drive them to be self-assembled via intermolecular Pt…Pt interactions into spherical aggregates of about 200 or 50 nm.Evaporation of the oil phase generates highly-stable aqueous dispersions of nanocrystals that emit a bright orange light as a result of the existence of^(3)MMLCT excited states.Different methods and conditions have been tested for studying the effect of several parameters such as the temperature and the stirring speed in the final particle size and in the polydispersity index.Moreover,the micro-and nanocrystals are able to entrap hydrophobic drugs between the alkyl chains of the compounds,forming stable dispersions of drug-loaded capsules in water.The droplet method is applied in the area of metallomesogens for the first time to synthesize self-assembled Pt(II)nanocapsules,which opens a new field of study that could allow the use of these liquid crystal materials in biomedical applications.

液晶金属配位聚合物的合成及性能

基于国内外最新研究文献 ,系统论述了近年来液晶金属配位聚合物的合成方法、液晶行为及应用前景。指出液晶金属配位聚合物的合成方法可归纳为直接配位法、单体配位法、交联配位法和聚合物反应法四种。液晶金属配位聚合物一般呈现热致液晶行为 ,显示稳定的向列液晶相或近晶液晶相。有些金属配位聚合物还呈现互变性近晶态或单变液晶性。液晶金属配位聚合物具有金属的特殊性质 ,是一种新型高性能磁导、电导和光导材料 ,可望应用于液晶显示材料、磁性信息储存薄膜材料、润滑剂和各向异性催化剂等。

溴原子取代对二茂铁液晶化合物介晶性的影响

Six novel ferrocene-containing compounds with structure of Fe-C 6H 4-O 2C-C 6H 3(Br)-OC 10 H 21 ,compound 7,and Fe-C 6H 4-N=CH-C 6H 4-O 2C-C 6H 3(Br)-OC nH 2n+1 (Fe:ferrocenyl;n=2,4,6,8,10,compound 8,9,10,11,12)(series Ⅰ)were prepared.Their mesogenic behaviors were studied with DSC and polarized microscopic.The result showsed that compoud 7 did not possess liquid crystalline properties,while series Ⅰ compounds had narrow liquid crystal temperature range.

Investigation of Intermetallic Compound Formed from Rapid Solidification of Al-Ti-RE Alloy

Al-Ti alloy containing rare earth elements can produce fine, uniform dispersion intermetallic phase through rapid solidification (RS) technology. RS Al-Ti-RE alloy can be designed for applications at elevated-temperature since the intermetallic compound has good thermal stability. A transmission electron microscopy investigation shows the intermetallic phase has a diamond cubic structure (a=1.47736 nm), with space group Fd3m. The chemical stoichiometry is Al_(20)Ti_2La. The particle is formed from the melting directly, prior to other phases, and the nucleus is formed from icosahedrons composed with twenty tetrahedrons. Twin crystal structure plays an important role in the nucleation stage.

Synthesis and Thermal Behaviour of Lanthanide Complexes of 4′[（Cholesteryloxy）Carbonyl]—Benzo—15—Crown—5

Lanthanide complexes of a steroid-substituted benzocrown ether were synthesised. The metal-to-ligand ratio of all the metal complexes is 1∶1. The ligand 4′-[(cholesteryloxy)carbonyl]-benzo-15-crown-5 is a monotropic liquid crystal, displaying a cholesteric mesophase. The lanthanide complexes with nitrate counter-ions form a highly viscous mesophase, decomposing at the clearing point. The transition temperatures change as a function of the lanthanide ion. The corresponding lanthanide complexes with dodecylsulphate (DOS) counter-ions do not form a mesophase. In both cases, the metal complexes have a much lower melting point than the parent ligand.

含二茂铁结构单元的苯并菲盘状液晶的合成及介晶性

通过两条合成路线制备了含二茂铁基的苯并菲盘状液晶化合物.差示扫描量热法(DSC)和热台偏光显微镜(POM)对化合物的介晶性研究结果显示,化合物具有柱状介晶相.

Solid State Structure and Lyotropic Mesomorphism of Rare-Earth Trisdode cylsulphates in the Water-Ethylene Glycol System

The phase behaviour of lanthanide(Ⅲ) dodecylsulphates, Ln(C 12 H 25 SO 4) 3, by thermo optical microscopy using Lawrence penetration technique was investigated. The lyotropic phase behaviour of lanthanide(Ⅲ) dodecylsulphates in ethylene glycol water in mixtures hereof, depends on the composition of the solvent. For pure ethylene glycol and mixtures of ethylene glycol and water three different mesophases are formed, i.e. a lamellar, a cubic and a hexagonal phase, whereas when water is used as solvent no cubic phase is formed. The size of the lanthanide ion has no influence on the mesomorphism of these metallomesogens, although the smaller the lanthanide ion the lower the solubility.

Mesomorphism of Lanthanide(Ⅲ) 4-Hexyloxybenzoates

The 4-alkoxybenzoic acids are well-known liquid crystals showing several mesophases (nematic, smectic C phase or both) depending on the alkoxy chain length and whereby the rigid core of the mesogen is formed by intermolecular hydrogen bonds. In this paper it is shown that the thermal behaviour of lanthanide salts of 4-hexyloxybenzoic acids depends on the lanthanide ion (Ln=La, Pr, Nd, Sm, Eu). The lanthanum(Ⅲ) and praseodymium(Ⅲ) 4-hexyloxybenzoates exhibit a smectic A mesophase. No mesophase is found for the corresponding compounds of heavier lanthanides. The thermal properties of the lanthanide(Ⅲ) 4-hexyloxybenzoates were investigated by differential scanning calorimetry (DSC), polarising thermo-optical microscopy and synchrotron X-ray radiation.

Mesomorphic Studies on a Series of Nickel (II) Centered Aromatic Complexes Displaying Liquid Crystalline Phases

Two new series (A & B) of three materials each based on the aroyl hydrazinato-nickel (II) complex were synthesized and characterized. The core molecule in these series consists of two 4-benzoyloxy benzylidene moieties and two benzene rings attached at the azomethine moiety. These latter benzene rings have one or two alkoxy chains comprised of either 10, 12, 16 or 18 carbon atoms. The characterization of these two series by polarized optical microscopy and differential scanning calorimetry is described herein. Upon cooling from the Isotropic phase, three of the six materials display a monophasic columnar phase and the other three possess a biphasic nematic and columnar phases. Upon heating, all six materials have a clearance point at high temperatures without displaying mesomorphic behavior. In series B mesogens, it was observed that the longer the hydrocarbon tail length, the lower the clearance point.

新型有机汞类液晶的合成及其相变研究

设计并合成了一类新型的双［（４－ｎ－烷氧基苯基）乙炔基］汞液晶，其相变行为通过ＤＳＣ及偏光显微镜进行了测试及观察。该类化合物表现出很好的液晶行为。

液晶聚氨酯材料的合成及应用研究进展

简要介绍了液晶聚氨酯材料的分类,分析了主链型液晶聚氨酯与侧链型液晶聚氨酯的合成方法及其结构与性能。综述了液晶聚氨酯材料在液晶显示、光致诱导、形状记忆、生物医药等方面的研究与应用,并提出了其今后的发展方向。