Luminescence properties of the ternary terbium complexes with (ortho and para) aminobenzoic acids and 1,10-phenanthroline incorporated in silica matrix by a sol-gel method

Ternary complexes of terbium with ortho (and pam) aminobenzoic acid and 1,10-phenanthroline were introduced into silica gel by the sol-gel method. The luminescence behavior of the solid-state samples was studied during the sol-gel aging process by means of emission. excitation spectra, lifetimes and quantum efficiencies.

The synthesis, luminescence and energy transfer of the binary and ternary complexes of rare earth with aminobenzoic acids and 1,10-phenanthroline

Thirteen kinds of binary and ternary complexes of rare earth (Gd, Eu,Tb) with ortho (para) aminobenzoic acid and 1.10--phenanthroline were synthesized and characterized. The phosphorescence spectra and lifetimes of gadolinium complexes were measured and the lowest triplet state energies of ligands and the energy transfer efficiencies between ligands were determined. The luminescence properties and intramolecular energy transfer of these complexes were studied in details.

Effect of structures of modifiers on electrochemistry of di-mu-oxo dimanganese 2,2'-bipyridine complex

The gold electrodes modified with 2-picolinic acid , nicotinic acid, iso-nicotinic or thiophene were prepared using membrane transfer method, The electrochemistry of di-mu-oxodimanganese 2,2'-bipyridine complex was studied in the acetic acid buffer solution at different modified gold electrodes, It was found that the modifiers which can promote the electrochemical reaction of the complex should be of at least two functional groups, One group can be bound to the electrode surface and the other can form electron transfer pathway between the modifier and the complex through sal; bridge or hydrogen bond, In addition, the mechanism of the electrochemical reaction was discussed.

SIMULTANEOUS DETERMINATION OF GUANINE, URIC-ACID, HYPOXANTHINE AND XANTHINE IN HUMAN PLASMA BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH AMPEROMETRIC DETECTION

A reversed-phase high-performance liquid chromatographic method with amperometric detection is described for the separation and quantification of uric acid, guanine, hypoxanthine and xanthine. The isocratic separation of a standard mixture of the compounds was achieved in 5 min on a Spherisorb 5 C-18 reversed-phase column, with a mobile phase of NaH2PO4 (300 mmol dm(-3) pH 3.0)-methanol-acetonitrile-tetrahydrofuran (97.8 + 0.5 + 1.5 + 0.2). Uric acid, guanine, hypoxanthine and xanthine were completely separated, with detection limits in the range 2-20 pmol per injection. The effect of pH and the composition of the mobile phase on the separation are described. The hydrodynamic voltammograms of these compounds were recorded at a glassy carbon electrode. The linear range of the calibration graph for each compound was: uric acid; 1-5000 mu mol dm(-3); guanine, 0.5-2000 mu mol dm(-3); hypoxanthine, 0.1-500 mu mol dm(-3) and xanthine, 0.5-5000 mu mol dm(-3). The within- and between-day precision was good. The uric acid and hypoxanthine content in human plasma was measured using the proposed method. Good recoveries of uric acid (97.9-103%), hypoxanthine (98.0-99.2%), guanine (96.0-98.3%) and xanthine (96.0-102%) were obtained from human plasma. The results of electrochemical detection were in good agreement with those of UV detection.

A new sesquiterpene-substituted benzoic acid from the brown alga Dictyopteris divaricata.

A new sesquiterpene-substituted benzoic acid has been isolated from the brown Alga Dictyopteris divaricata Okam.. Its structure was elucidated as 3-[(2-hydroxy-2,5,5,8a-tetramethyldecahydro-1-naphthalenyl)methyl]-4-hydroxybenzoic acid, named dictyvaric acid on the basis of spectroscopic methods including IR, HRFABMS, 1D and 2D NMR techniques.

鹿角蕨化学成分及生物活性的研究

鹿角蕨(Platycerium wallichii Hook.)是鹿角蕨科鹿角蕨属植物，为国家二级保护植物。该植物主要分布在云南西南部盈江县那邦坝，在当地用作跌打药。有关鹿角蕨属的系统关系存在一些假设，关于鹿角蕨属植物化学成分及生物活性的研究未见报道。从鹿角蕨（Platycerium wallichii Hook.）叶95%乙醇提取物中，我们分离得到了七个已知化合物。根据理化常数及波谱数据 (IR、UV、MS及NMR)，其结构分别鉴定为：(I)β一谷甾醇、(II)胡萝卜甙、 (III)2-propenoic acid,3一[(2R, 3S)-2，3-dihydro-2- (4-hydroxy-3-methoxyphenyl) -3- (hydroxymethyl) -7-mnethoxy-5-benzofuranyll -、(Ⅳ)松脂素-4’-0-β -D-葡萄糖甙、(v)松腊素、(Ⅵ)2，5_二羟基苯甲酸甲酯、(Ⅶ)槲皮素3-0-β -半乳糖甙。七个成分均为首次从该种植物中获得。 我们对鹿角蕨(Platvcerium wallichii Hook.)能育叶部分以及基生叶部分的乙醇提取物进行了镇痛试验和抗炎试验，试验表明鹿角蕨（Platvcerium wallichii Hook.）的叶有弱镇痛作用。

Isolation, characterization and genome sequence of a birnavirus strain from flounder Paralichthys olivaceus in China

A birnavirus strain, Paralichthys olivaceus birnavirus (POBV), was isolated and characterized from cultured flounder in China, and its complete genomic sequence was subsequently determined. The virus could induce cytopathic effects (CPE) in four of seven fish cell lines and was resistant to chloroform, 5-iodo-2'-deoxyuridine, acid and alkaline pH, and heat treatment. Purified virus particles had a typical icosahedral shape, with a diameter of approximately 55-60 nm. The genomic segments A and B of POBV were 3,091 and 2,780 bp in length and shared many of the features of the members of the family Birnaviridae. Segment A contained two partially overlapping ORFs encoding a polyprotein, pVP2-VP4-VP3, and a nonstructural protein, VP5, while segment B had only one ORF encoding for the VP1, a viral RNA-dependent RNA polymerase (RdRp). This is the first report about a birnavirus strain from a new non-salmonid host in China and its complete genome sequence.

CYCLIC PEPTIDE HEPATOTOXINS FROM FRESH-WATER CYANOBACTERIAL (BLUE-GREEN-ALGAE) WATERBLOOMS COLLECTED IN CENTRAL CHINA

Toxic cyanobacteria (blue-green algae) waterblooms have been found in several Chinese water bodies since studies began there in 1984. Waterbloom samples for this study contained Anabaena circinalis, Microcystis aeruginosa and Oscillatoria sp. Only those waterblooms dominated by Microcystis aeruginosa were toxic by the intraperitoneal (i.p.) mouse bioassay. Signs of poisoning were the same as with known hepatotoxic cyclic peptide microcystins. One toxic fraction was isolated from each Microcystis aeruginosa sample. Two hepatotoxic peptides were purified from each of the fractions by high-performance liquid chromatography and identified by amino acid analysis followed by low and high resolution fast-atom bombardment mass spectrometry (FAB-MS). LD50 i.p. mouse values for the two toxins were 245-mu-g/kg (Toxin A) and 53-mu-g/g (Toxin B). Toxin content in the cells was 0.03 to 3.95 mg/g (Toxin A) and 0.18 to 3.33 mg/kg (Toxin B). The amino acid composition of Toxin A was alanine [1], arginine [2], glutamic acid [1] and beta-methylaspartic acid [1]; for Toxin B it was the same, except one of the arginines was replaced with a leucine. Low- and high-resolution FAB-MS showed that the molecular weights were 1,037 m/z (Toxin A) and 994 m/z (Toxin B), with formulas of C49H76O12N13 (Toxin A) and C49H75O12N10 (Toxin B). It was concluded that Toxin A is microcystin-RR and Toxin B is microcystin-LR, both known cyclic heptapeptide hepatotoxins isolated from cyanobacteria in other parts of the world. Sodium borohydride reduction of microcystin-RR yielded dihydro-microcystin-RR (m/z = 1,039), an important intermediate in the preparation of tritium-labeled toxin for metabolism and fate studies.

能同时高对映选择性还原酮和亚胺的有机小分子催化体系的设计与合成

不对称催化还原反应是当今有机化学研究中最具活力的研究方向之一。在这一研究领域中，已有不少催化剂体系能够对前手性酮或亚胺进行高对映选择性还原，但极少能够对酮和亚胺同时具有很好的催化效果。本论文从光学纯的哌啶酸出发，设计与合成了一系列结构简单、合成方便的手性有机小分子路易斯碱催化剂，并研究了该系列催化剂在酮和亚胺不对称还原本课题组前期研究中开发出L-哌啶酸和（1S,2R）-1,2-二苯基氨基乙醇衍生的路易斯碱催化剂，在三氯氢硅对亚胺的还原反应中显示出很高的催化活性和对映选择性，但对酮的还原却没有得到很理想的催化效果。本研究对该催化剂进行一定的结构改造和修饰，获得了能够同时高对映选择性催化还原酮和亚胺两类底物的有机小分子催化剂。通过优化条件，取得了很好的收率（高达99%）和对映选择性（高达93%的ee 值）。而且，其底物普适性也是前所未有的，对芳香酮和脂肪酮，芳香亚胺和脂肪亚胺都具有很好的催化效果。通过机理方面的探讨，我们推测该催化体系对酮的还原和对亚胺的还原反应可能分别采用了七配位和六配位过渡态模型。Asymmetric reduction is one of the most active research areas in modernasymmetric synthesis. A number of highly efficient methods have been developed forthe asymmetric reduction of either ketones or ketimines. However, there have beenextremely rare examples of catalytic systems that allow for highly enantioselectivereductions of both ketones and ketimines.In this study, starting from optically pure pipecolinic acid, we designed andsynthesized a series of structurally simple and easily accessible chiral organic Lewisbasic catalysts and employed them in asymmetric reduction of ketones and ketimines.Previously our group has developed a highly enantioselective Lewis basiccatalyst for the asymmetric reduction of ketimines by trichlorosilane starting fromL-piperdine-2-carboxylic acid and (1R,2S)-2-amino-1,2-diphenylethanol. But thiscatalyst was found not to be very effective in the asymmetric reduction of ketones.Slight modifications of this catalyst has led to a new highly enantioselective catalystapplicable for the reduction of both ketones and ketimines by trichlorosilane. Underthe optimal conditions, this catalyst afforded excellent yields (up to 99%) andenantioselectivities (up to 93% ee). Moreover, an unprecedented substrate spectrumwas observed with this catalyst, which are highly effective for aromatic and aliphaticketones as well as aromatic and aliphatic ketimines. A heptacoordinate silicontransition structure and a hexacoordinate one were proposed for the reduction of ketones and ketimines, respectively.

手性有机小分子路易斯碱催化剂的设计、合成及其在亚胺不对称还原中的应用

手性胺是合成天然产物和手性药物的重要中间体，亚胺的不对称催化还原是制备光学活性手性胺的最直接有效的方法之一。但是，由于C＝N双键的反应活性较弱以及容易发生E/Z异构等问题，亚胺的不对称催化还原具有很大的挑战性，既具有高对映选择性又具有宽广底物普适性的催化剂很少。 本文分别由手性脯氨酸、哌啶酸、哌嗪酸以及氨基醇出发，设计和合成了一系列结构新颖、合成简便、性能优良的酰胺类有机小分子路易斯碱催化剂，以廉价的三氯氢硅为氢源，用这些催化剂催化亚胺不对称还原，得到了非常优良的收率、对映选择性和前所未有的底物普适性。 文献研究认为，除N-甲酰基外，分子内含有芳香酰胺是能催化亚胺还原的有机小分子路易斯碱催化剂具有较高对映选择性的必要条件，我们研究发现N-甲酰脯氨酸非芳香酰胺类催化剂（包括结构简单的C2-对称型脯氨酰胺类催化剂），对N-芳基酮亚胺的还原可获得达86%的对映选择性，远高于同类芳香酰胺催化剂，证明N-甲酰非芳香酰胺类路易斯碱催化剂在亚胺还原中也能得到高的对映选择性。 在进一步研究中，我们以手性六元哌啶酸为模板，分别设计合成了N-甲酰哌啶酸芳香酰胺和N-甲酰哌啶酸非芳香酰胺两类催化剂，其中芳香酰胺催化剂（S）-N-（甲酰基）哌啶-2-酸-1-萘基酰胺（28）和非芳香酰胺催化剂（2S,1'S,2'S）-N-（甲酰基）-哌啶-2-酸（1',2'-二苯基-2'-乙酰氧基-乙基）酰胺（30）显示出非常优良的催化活性和对映选择性，对于N-芳基芳香酮亚胺的还原，无论是缺电子体系还是富电子体系，绝大部分都能得到很高的收率（达98%）和对映选择性（达96% ee)。特别值得一提的是30对一些脂肪族亚胺和α,β-不饱和亚胺的还原，虽然底物为E/Z混合物，也能得到很高的收率（达93%）和对映选择性（达95% ee)，这样的底物普适性在过渡金属催化体系中也是前所未有的。 现有的催化亚胺还原的高对映选择性催化体系大多仅适用于甲基酮亚胺底物，对位阻较大的非甲基酮亚胺很难获得好的结果。我们以L-哌嗪酸为模板设计和合成出的（S）-N-（甲酰基）-哌嗪-2-酸-4-对叔丁基苯磺酰基-苯基酰胺不但对N-芳基甲基酮亚胺有很好的对映选择性（达90% ee)，而且对于大位阻的N-芳基非甲基酮亚胺有更好的对映选择性（达97% ee)。该催化剂与30在底物普适性方面具有很好的互补性。 我们还设计了基于1,2-二苯基氨基醇为模板的新型N-甲酰路易斯碱有机小分子催化剂，首次发现结构简单的N-甲酰（1S,2R）二苯基氨基醇能较好的催化N-芳基酮亚胺，最高可以得到82%的对映选择性。 针对我们设计合成的结构新颖、性能优良的催化剂，我们对催化机理进行了探讨和解释，提出了几个假想的机理模型。 Catalytic enantioselective reduction of imines represents one of the most straightforward and efficient methods for the preparation of chiral amines, an important intermediate for the synthesis of natural products and chiral drugs. However, asymmetric reduction of imines remains a big challenge and highly enantioselective catalysts with a satisfactorily broad substrate scope remain elusive. Factors contributing to the difficulty of this transformation include the weak reactivity of the C=N bond and the existence of inseparable mixtures of E/Z isomers. Starting from chiral proline, pipecolinic acid, piperazine-2-carboxylic acid and 1,2-diphenyl amino alcohol, a series of structurally simple and easily prepared amides were developed as highly effective Lewis basic organocatalysts for the asymmetric reduction of imines with trichlorosilane as the reducing agent, which promoted the reduction of N-aryl imines with high yields and excellent enantioselectivities with an unprecedented substrate spectrum. In the literature, it has been believed that besides the N-formyl group, the existence of an arylamido group in the structure of Lewis basic organocatalysts is a prerequisite for obtaining high enantioselectivity in the catalytic reduction of imines. However, we found that the N-formyl-L-prolinamides bearing non-arylamido groups, including structurally simple C2-symmetric tetraamides, could also work as effective Lewis basic catalysts to promote the asymmetric reduction of ketimines with high enantioselectivities (up to 86% ee), which are even more enantioselective than the analogues with arylamido groups. In further studies, we developed novel N-formamides with arylamido groups and non-arylmido groups as Lewis basic catalysts using the commercially available L-pipecolinic acid as the template. The catalysts (S)-1-formyl-piperidine-2-carboxylic acid naphthylamide 28 and (2S,1'S,2'S)-acetic acid 2-[(1-formyl-piperidine-2-carbonyl) -amino]-1,2-diphenyl-ethyl ester 30 were found to promote the reduction of a broad range of N-aryl imines in high yields (up to 98%) and excellent ee values (up to 96%) under mild conditions. Furthermore, catalyst 30 also exhibited high enantioselectivities (up to 95% ee) for the challenging aliphatic ketimines and α,β-unsaturated imines despite that these imines exist as E/Z isomeric mixtures. The broad substrate spectrum of this catalyst is unprecedented in catalytic asymmetric imine reduction, including transition-metal-catalyzed hydrogenation processes. Many of the currently available highly enantioselective catalytic systems only tolerate methyl ketimines, which gave poor results for bulkier non-methyl ketimines. Starting from L-piperazine-2-carboxylic acid, we developed (S)-4-(4-tert- butylbenzenesulfonyl)-1-formyl-N-phenyl-piperazine-2-carboxamide as highly enantioselective Lewis basic catalysts for the hydrosilylation of both methyl ketimines and steric bulky non-methyl ketimines. Moreover, higher enantioselectivities were obtained for non-methyl ketimines than methyl ketimines under the catalysis of this catalyst. Thus, this catalyst system complements with 30 in terms of the substrate scope. We also found that easily accessible (1R,2S)-N-formyl-1,2-diphenyl- 2-aminoethanol worked as an effective Lewis basic catalyst in the enantioselective hydrosilylation of ketimines, affording high enantioselectivities (up to 82% ee) for a broad range of ketimines. To rationalize the high efficiencies of the structurally novel catalysts we developed, several catalytic models have been proposed.

Validation and in situ application of an automated dissolved nickel monitor for estuarine studies

The validation of a fully automated dissolved Ni monitor for in situ estuarine studies is presented, based on adsorptive cathodic stripping voltammetry (AdCSV). Dissolved Ni concentrations were determined following on-line filtration and UV digestion, and addition of an AdCSV ligand (dimethyl glyoxime) and pH buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid). The technique is capable of up to six fully quantified Ni measurements per hour. The automated in situ methodology was applied successfully during two surveys on the Tamar estuary (south west Britain). The strongly varying sample matrix encountered in the estuarine system did not present analytical interferences, and each sample was quantified using internal standard additions. Up to 37 Ni measurements were performed during each survey, which involved 13 h of continuous sampling and analysis. The high resolution data from the winter and summer tidal cycle studies allowed a thorough interpretation of the biogeochemical processes in the studied estuarine system.

Identification of Phenylethanoid Glycosides in Plant Extract of Plantago asiatica L. by Liquid Chromatography-Electrospray Ionization Mass Spectrometry

The present work describes a liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method for rapid identification of phenylethanoid glycosides in plant extract from Plantago asiatica L. By using a binary mobile phase system consisting of 0.2% acetic acid and acetonitrile under gradient conditions, a good separation was achieved on a reversed-phase C-18 column. The [M-H](-) ions, the molecular weights, and the fragment ions of phenylethanoid glycosides were obtained in the negative ion mode using LC-ESI-MS. The identification of the phenylethanoid glycosides (peaks 1-3) in the extract of P. asiatica L. was based on matching their retention time, the detection of molecular ions, and the fragment ions obtained by collision-induced dissociation (CID) experiments with those of the authentic standards and data reported in the literature.

Tuning the Energy Level of Organic Sensitizers for High-Performance Dye-Sensitized Solar Cells

Cost-effective organic sensitizers will play a pivotal role in the future large-scale production and application of dye-sensitized solar cells. Here we report two new organic D-pi-A dyes featuring electron-rich 3,4-ethylenedioxythiophene- and 2,2'-bis(3,4-ethylenedioxythiophene)-conjugated linkers, showing a remarkable red-shifting of photocurrent action spectra compared with their thiophene and bithiophene counterparts. On the basis of the 3-f{5'-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]-2,2'-bis(3,4-ethylenedioxythiophene)-5-yl}2-cyanoacrylic acid dye, we have set a new efficiency record of 7.6% for solvent-free dye-sensitized solar cells based on metal-free organic sensitizers. Importantly, the cell exhibits an excellent stability, keeping over 92% of its initial efficiency after 1000 h accelerated tests under full sunlight soaking at 60 degrees C. This achievement will considerably encourage further design and exploration of metal-free organic dyes for higher performance dye-sensitized solar cells.

Fabrication and characterization of SERS-active silver clusters on glassy carbon

In this article, a novel technique for the fabrication of surface enhanced Raman scattering (SERS) active silver clusters on glassy carbon (GC) has been proposed. It was found that silver clusters could be formed on a layer of positively charged poly(diallyldimethylammonium) (PDDA) anchored to a carbon surface by 4-aminobenzoic acid when a drop containing silver nanoparticles was deposited on it. The characteristics of the obtained silver clusters have been investigated by atomic force microscopy (AFM), SERS and an SERS-based Raman mapping technique in the form of line scanning. The AFM image shows that the silver clusters consist of several silver nanoparticles and the size of the clusters is in the range 80-100 nm. The SERS spectra of different concentrations of rhodamine 6G (R6G) on the silver clusters were obtained and compared with those from a silver colloid. The apparent enhancement factor (AEF) was estimated to be as large as 3.1 x 10(4) relative to silver colloid, which might have resulted from the presence of 'hot-spots' at the silver clusters, providing a highly localized electromagnetic field for the large enhancement of the SERS spectra of R6G. The minimum electromagnetic enhancement factor (EEF) is estimated to be 5.4 x 10(7) by comparison with the SERS spectra of R6G on the silver clusters and on the bare GC surface.

Sulfonated polyimides bearing benzimidazole groups for proton exchange membranes

A series of sulfonated polymides containing benzimidazole groups were synthesized using 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS) as the sulfonated diamine, and 2-(3',5-diaminophenyl)benzimidazole (a) or 6,4'-diamino-2-phenylbenzimidazole (b) as the nonsulfortated diamine. The electrolyte properties of the synthesized polyimides Ia-x, Ib-x, x refers to molar percentage of the sulfonated diamine) were investigated and compared with those of polyimides (Ic-x) from BTDA, ODADS, and m-phenylenediamine (c). All synthesized polyimides possessed high molecular weights revealed by their high viscosity, and formation of tough and flexible membranes. Polyintides with benzimidazole groups exhibited much better swelling capacity than those without benzimiclazole groups. This was attributed to the strong interchain interaction through basic benzimidazole functions and sulfonic acid groups. The sulfortated polyimides that are incorporated with 1, 1',8,8'-binaphthalimide exhibited better hydrolytic stability than that with 1,4,5,8-naphthalimide. Polyimide membranes with good water stability as well as high proton conductivity were developed. Polyimide membrane (Ia - 90), for example, did not lose mechanical properties after being soaked in boiling water for tOOO h, while its proton conductivity was still at a high level (compared to that of Nafion 117).