Synthesis and characterisation of novel imidazolium-based ionic liquid crystals with a p-nitroazobenzene moiety

A novel series of compounds with different counter anions, i.e. 1-{[4-(4-nitrophenylazo)phenyloxy]}alkyl-3-methyl-1H-imidazol-3-ium bromide salts (C-n , n=3, 6, 10) and tetrafluoroborate salts (D-n , n=3, 6, 10), were synthesised by the incorporation of an imidazolium group into paraffin side chain-terminated 4-nitroazobenzene derivatives. Their chemical structures were determined by H-1 NMR, C-13 NMR, UV spectroscopy and elemental analysis.

Synthesis of macrocyclic arylene ketone oligomers containing the phthaloyl moiety by Friedel-crafts acylation reaction

Two kinds of macrocyclic arylene ketone oligomers have been synthesized in high yield from phthaloyl dichloride and various bridge-linking electron-rich aromatic hydrocarbons via the modified Friedel-Crafts acylation reaction. The presence of a Lewis base in this reaction is demonstrated to be advantageous for forming macrocycle oligomers. These resultant oligomers can undergo melt ring-opening polymerization to give polymers with high T. and excellent thermal stability.

Blue light-emitting poly(fluorene-co-benzene) containing an oxadiazole moiety

A new kind of polyfluorene containing oxadiazole as the side chain was synthesized. The introduction of oxadiazole moiety as more bulky group prevents the aggregation and reduces the crystallinity of the polymers. Efficient intramolecular energy transfer from oxadiazole moiety to the conjugated backbone has been realized, leading to 70% improvement of photoluminescence quantum efficiency of the designed polymers. Compared with PAF, the PFOXD exhibits significant improvement in electroluminescence properties, with luminous efficiency of 0.8 cd/A and maximum luminance of 1800 cd/m(2).

Novel PPV-based light-emitting copolymers containing triazole moiety

Two new light-emitting PPV-based copolymers bearing electron-withdrawing triazole unit in the main chain have been synthesized by Wittig reaction between triazole diphosphonium salt and the corresponding dialdehyde monomers, respectively. Their optical and physical properties are characterized by UV-vis, photoluminescence (PL), TGA and DSC. The resulting copolymers are highly soluble in common organic solvents and have high Tg and Td values. They show blue-greenish fluorescence in solution (lambda(max) 502 and 508 nm) and green fluorescence in the solid state (lambda(max) 520 and 526 nm), respectively.

Novel polyquinolines containing phenylamine moiety

Two novel conjugated polyquinolines (F-PA-PQ and Cz-PA-PQ) with the phenylamine moiety as hole-transporting segment were synthesized. The resulting polyquinolines exhibited excellent thermal stabilities (Tg > 200degreesC), good solubility in common organic solvents and film-forming properties. Their optical absorption, photoluminescence, electroluminescence and sensory properties were studied.

Synthesis and properties of PPP-based copolymers containing phenothiazine moiety

Novel soluble alternating conjugated copolymers (PFSP and PFSR) comprised of phenothiazine unit are synthesized by palladium-catalyzed Suzuki coupling reactions. Their thermal stability, photoluminescence, electroluminescence, hole injection and transport properties are investigated. The resulting copolymers exhibit good thermal stability and excellent hole-injection ability (about -5.2eV), which are closely matched to the work function of ITO. Double-layer devices demonstrate that PFSP is a promising hole-transporting material for electroluminescent devices.

Novel PPV-based light-emitting polymers containing siloxane moiety

Two PPV-based copolymers consisting siloxane linkage have been synthesized by melt condensation of bisphenol and dianilinodimethylsilane. The rigid PPV segments act as chromosphere and allow fine turning of band gap for blue-light emission, while the flexible siloxane units lead to the effective interruption of conjugation and the enhancement of solubility. The UV-vis absorption, photoluminescent and eletroluminescent properties have been studied.

New sphingolipids with a previously unreported 9-Methyl-C-20-sphingosine moiety from a marine algous endophytic fungus Aspergillus niger EN-13

Asperamides A (1) and B (2), a sphingolipid and their corresponding glycosphingolipid possessing a hitherto unreported 9-methyl-C-20-sphingosine moiety, were characterized from the culture extract of Aspergillus niger EN-13, an endophytic fungus isolated from marine brown alga Colpomenia sinuosa. The structures were elucidated by spectroscopic and chemical methods as (2S,2'R,3R,3'E,4E,8E)-N-(2'-hydroxy-3'-hexadecenoyl)-9-methyl-4,8-icosadien-1,3-diol (1) and 1-O-beta-D-glucopyranosyl-(2S,2'R,3R,3'E,4E,8E)-N-(2'-hydroxy-3'-hexadecenoyl)-9-methyl-4,8-icosadien-1,3-diol (2). In the antifungal assay, asperamide A (1) displayed moderate activity against Candida albicans.

Lancifodilactone G: A unique nortriterpenoid isolated from Schisandra lancifolia and its anti-HIV activity

Lancifodilactone G (1), a novel, highly oxygenated nortriterpenoid featuring a partial enol structure and a spirocyclic moiety, was isolated from the medicinal plant Schisandra lancifolia. Its structure and stereochemistry were determined from extensive one- and two-dimensional NMR and mass spectral data, coupled with single-crystal X-ray analysis. Compound 1 exerted minimal cytotoxicity against C8166 cells (CC50 > 200 mu g/mL) and showed anti-HIV activity with EC50 = 95.47 +/- 14.19 mu g/mL and a selectivity index in the range of 1.82-2.46.

Dichotomains A and B: Two new highly oxygenated phenolic derivatives from Dicranopteris dichotoma

Dichotomains A (1) and B (2), two new highly oxygenated phenolic derivatives that feature a spirodilactone moiety in their structures, were isolated from the fronds of Dicranopteris dichotoma. Their structures were elucidated on the basis of NMR and MS sp

Bioactive Nortriterpenoids from Schisandra grandiflora

Three new nortriterpenoids, schigrandilactones A-C (1-3), along with eight known compounds, were isolated from an organic solvent extract of Schisandra grandiflora. Compounds I and 2 feature a spirocyclic moiety in their structures, and compound 3 was cha

Synthesis of Zidovudine Derivatives with Anti-HIV-1 and Antibacterial Activities

Twelve novel zidovudine derivatives were prepared by modifying 5 '-hydroxyl group of sugar moiety (1-8) and 5-methyl group of thymidine nucleus (9-12) and characterized spectrally. The compounds were evaluated for anti-HIV-1, antitubercular and antibacter

环糊精衍生物的设计、合成及其对环辛烯光异构化研究

环糊精(Cyclodextrins, CDs)经化学修饰后可以得到各种类型的衍生物，不仅可以扩展其原有的键合能力，而且还可以改变其选择性，是当代超分子化学的一个研究热点。环糊精第二面的仲羟基比第一面的伯羟基有着更好的催化性能，第二面的选择性修饰将产生更多有价值的衍生物，可用于催化、酶模拟、手性识别等方面。 取代苯甲酰基修饰环糊精对顺式环辛烯(cis-cyclooctene)光异构化反应有非常重要的影响作用，苯环上取代基的性质和取代位置与产物的%ee值和对映体构型之间存在某种内在联系。有目的地选择适宜取代基，设计、合成新型环糊精光增感剂, 有可能按预定目的得到更高%ee值的反式环辛烯；同时，取代苯甲酰基修饰环糊精对cis-cyclooctene光异构化的增感机理有待于进一步阐明。 本论文工作对环糊精的化学修饰以及超分子体系对cis-cyclooctene不对称光异构化反应方面的进展进行了调研。合成了一系列单-6-位取代苯甲酰基修饰环糊精，用于cis-cyclooctene光异构化增感反应，并用圆二色光谱滴定法研究这些环糊精衍生物与cis-cyclooctene的相互作用，以探索光增感反应机理。在此基础上，探讨了环糊精第二面的选择性修饰方法。内容主要包括： 1. 简要介绍了超分子化学的概况，并对环糊精的选择性修饰方法和超分子体系对cis-cyclooctene不对称光异构化反应的主要成果和最新进展进行了评述。 2. 合成了12种单-6-O-(取代苯甲酰基)-β-环糊精，其中10种为新化合物。采用紫外光谱、红外光谱、核磁共振波谱以及质谱等手段对化合物的结构进行了表征。 3. 探索了直接选择性修饰环糊精第二面的便捷新方法。用取代苯甲酰咪唑酯为酰化试剂，0.2M碳酸盐缓冲溶液(pH=9.9)作催化剂，能够有效地活化2-位仲羟基，对环糊精第二面进行选择性修饰，此方法既简便又经济；同时，发现取代苯甲酰基能够在β-CD第二面的2-位、3-位羟基间相互迁移。 4. 用单-6-O-(取代苯甲酰基)-β-环糊精作光增感剂，对cis-cyclooctene光异构化反应进行研究。实验结果证明：取代苯甲酰基上的取代基性质、位置、长度对反应的对映选择性有很大影响；此外，反应体系溶剂极性对产物的%ee值和对映体构型也有重大影响。用单-6-O-(3-甲氧苯甲酰基)-β-CD作增感剂，cis-cyclooctene光异构化反应产物(R)-trans-cyclooctene的对映选择性为45.8%ee，是到目前为止取得的最好对映选择性。 5. 采用圆二色光谱滴定法研究环糊精衍生物与cis-cyclooctene的相互作用，计算包结物的平衡常数，研究包结物的相对稳定性，为探索光增感反应机理提供基础。我们猜测：电子效应对cis-cyclooctene光异构化反应的影响，可能比取代基位置对反应的影响更大，借助电子效应有希望获得更高的%ee值。 Cyclodextrins can be subjected to diverse modifications to give a wide variety of cyclodextrin derivatives, which could not only extend their original molecular binding ability, but also alter their molecular selectivity. Therefore, cyclodextrin chemistry is currently a significant topic in supramolecular chemistry. The more open secondary hydroxyl side of CDs is stated to be catalytically very important, modifications of this face are believed to produce valuable derivatives for catalysis, enzyme mimic, chiral discrimination, etc. Mono-6-O-(substituted benzoyl)-β-CDs as novel supramolecular photosensitizing hosts have recently excited considerable attention in photochirogenesis. The supramolecular photosenstization of cis-cyclooctene mediated by them gave chiral trans-cyclooctene, enantiomeric excess of which was critically affected by the substituent introduced to the sensitizer moiety. In order to enhance the photoenantiodifferentiating ability, and elucidate the origin mechanisms of substituent-dependent enantioselectivity, in this work a series of mono-6-O-(substituted benzoyl)-β-CDs have been synthesized, and applied for enantiodifferentiating photoisomerization of cis-cyclooctene. The major contents are as follows: 1. The general aspects of supramolecular chemistry were descibed briefly. The new progress and important achievements on methods of selective modification of cyclodextrin and supramolecular enantiodifferentiating photoisomerization of cis-cyclooctene were reviewed. 2. Twelve mono-6-O-(substituted benzoyl)-β-CDs including ten novel compounds have been synthesized. Their structures have been characterized by using UV-vis, IR, NMR and MS methods. 3. A new convenient strategy for direct acylation of β-cyclodextrin on the secondary hydroxyl face was achieved by using the combination of N-benzoylimidazole and carbonate buffer in DMF, and the acyl migration between the C-2 and C-3 hydroxyl groups of β-cyclodextrin was found. 4. Experiments using mono-6-O-(substituted benzoyl)-β-CDs as chiral sensitizing hosts for mediating the enantiodifferentiating photoisomerization of cis-cyclooctene, were carried out. The results indicate that enantiomeric excess was critically affected, or even switched in sign, by the substituent introduced to the sensitizer moiety, and polarity of solvent. Using mono-6-O-(3-methoxybenzoyl)-β-CD as chiral sensitizing host, (R)-trans-cyclooctene was obtained in up to 45.8% enantiomeric excess, which is the highest value ever reported for supramolecular photochirogenesis with analogous hosts. 5. The conformational variation of these modified CDs and their complexation behaviors with cis-cyclooctene were examined by circular dichroism spectroscopy in water-methanol mixed solvents, which reveal that the orientation of chromophore was highly sensitive to the type, position and length of the introduced substituents. In the end, the complex stability constants(Ks) were calculated, and the mechanisms of reaction were discussed. Maybe, electronic effects are more important than positions of substituents for mediating the enantiodifferentiating photoisomerization of cis-cyclooctene.

Synthesis of novel ferrocenylphosphine-amidine ligands with central and planar chirality and their diastereomeric effect in Pd-catalyzed asymmetric allylic alkylation

Some novel ferrocenylphosphine-amidine ligands with central and planar chirality were prepared from (R,S-p)-PPFNH2-R 3 and its diastereomer (S,S-p)-PPFNH2 3a. The efficiency and diastereomeric impact of these ferrocenylphosphine-amidine ligands in the palladium-catalyzed asymmetric allylic substitution was examined, and up to 96% e.e. with 98% yield was achieved by the use of ligand (R,S-p)-4a with a methyl group in the amidino moiety. The results also indicated that (R)-central chirality and (S-p)-planar chirality in these ferrocenylphosphine-amidine ligands were matched for the palladium-catalyzed asymmetric allylic alkylation. (C) 2003 Elsevier Ltd. All rights reserved.

Bonding and correlation analysis of various SiCO isomers

The structural properties for various SiCO isomers in the singlet and triplet states have been investigated using CASSCF methods with a 6-311 +G* basis set and also using three DFT and MP2 with same basis set for those systems except for the linear singlet state. The detailed bonding character is discussed, and the state-state correlations and the isomerization mechanism are also determined. Results indicate that there are four different isomers for each spin state, and for all isomers, the triplet state is more stable than the corresponding singlet state. The most stable is the linear SiCO ((3)Sigma(-)) species and may be refer-red to the ground state. At the CASSCF-MP2(full)/6-311+G* level, the state-state energy separations of the other triplet states relative to the ground state are 43.2 (cyclic), 45.2 (linear SiOC), and 75.6 kcal/mol (linear CSiO), respectively, whereas the triplet-singlet state excitation energies for each configuration are 17.3 (linear SiCO), 2.2 (cyclic SiCO), 10.2 (linear SiOC), and 18.5 kcal/mol (linear CSiO), respectively. SiCo ((3)Sigma(-)) may be classified as silene (carbonylsilene), and its COdelta- moiety possesses CO- property. The dissociation energy of the ground state is 42.5 kcal/mol at the CASSCF-MP2(full)/6-311+G* level and falls within a range of 36.5-41.5 kcal/mol at DFT level, and of 23.7-28.9 kcal/mol at the wave function-correlated level, whereas the vertical IP is 188.8 kcal/mol at the CASSCF-MP2(full)/6-311+G* level and is very close to the first IP of Si atom. Three linear isomers (SiCO, SiOC, and CSiO) have similar structural bonding character. SiOC may be referred to the iso-carbonyl Si instead of the aether compound, whereas the CSiO isomer may be considered as the combination of C (the analogue of Si) with SiO (the analogue of CO). The bonding is weak for all linear species, and the corresponding potential energy surfaces are flat, and thus these linear molecules are facile. Another important isomer is of cyclic structure, it may be considered as the combination of CO with Si by the side pi bond. This structure has the smallest triplet state-singlet state excitation energy (similar to2.2 kcal/mol); the C-O bonds are longer, and the corresponding vibrational frequencies are significantly smaller than those of the other linear species. This cyclic species is not classified as an epoxy compound. State-state correlation analysis and the isomerization pathway searches have indicated that there are no direct correlations among three linear structures for each spin state, but they may interchange by experiencing two transition states and one cyclic intermediate. The easiest pathway is to break the Si-O bond to go to the linear SiCO, but its inverse process is very difficult. The most difficult process is to break the C-O bond and to go to the linear CSiO.