Reversed-phase HPLC of polymer additives with multiple on-line spectroscopic analysis (UV,IR, (1)H NMR and MS)

The reversed-phase chromatography of a number of polymer additives has been undertaken with on-line characterisation via a combination of diode array UV, (1)H NMR, IR spectroscopy and mass spectrometry. This combination of spectrometers enabled the on-flow collection of full UV, (1)H NMR, IR and mass spectra for a range of common polymer additives in amounts ranging from ca. 230 to 900 micro g on-column. The practical difficulties associated with multiple hyphenation and potential future developments are discussed.     

Spectroscopic characterisation and identification of ecdysteroids using high-performance liquid chromatography combined with on-line UV--diode array, FT-infrared and 1H-nuclear magnetic resonance spectroscopy and time of flight mass spectrometry

A prototype multiply hyphenated reversed-phase HPLC system has been applied to the analysis of a mixture of pure ecdysteroids and an ecdysteroid-containing plant extract. Characterisation was achieved via a combination of diode array UV, ¹H NMR, FT-IR spectroscopy and time of flight (TOF) mass spectrometry. This combination of spectrometers allowed the collection of UV, ¹H NMR, IR and mass spectra for a mixture of pure standards enabling almost complete structural characterisation to be performed. The technique was then applied to a partially purified plant extract in which 20-hydroxyecdysone and polypodine B were identified despite incomplete chromatographic resolution and the presence of co-chromatographing interferents. The experimental difficulties in the use of such a systems for these analytes are described.     

meso-四(烷氧基苯基)卟啉及其金属络合物的波谱研究

采用^1H NMR、MS、IR、UV、元素分析等分析测试表征手段确证了所合成的10个系列卟啉及其金属络合物的结构,研究了不同位置、不同链长烷氧基四苯基卟啉和不同金属离子卟啉络合物的结构与^1HNMR、IR和UV等波谱之间的关系,总结了卟啉配体及其金属络合物的^1H NMR、IR和UV判据,报道和解释了meso-四(烷氧基苯基)卟啉铜、锰络合物和meso-四(邻烷氧基苯基)卟啉钴络合物的^1H NMR研究结果,通过MS、^1H NMR、IR、UV、元素分析确证了我们所合成的铁卟啉为μ-氧桥联夹心二聚体结构,且存在两种典型构象,导致同系列络合物有四种类型^1H NMR谱图。     

Mass spectrometrically detected directly coupled high performance liquid chromatography/nuclear magnetic resonance spectroscopy/mass spectrometry for the identification of xenobiotic metabolites in maize plants

Reconstructed ion chromatograms have been used to identify relevant high performance liquid chromatography (HPLC) peaks in a directly coupled high performance liquid chromatography/nuclear magnetic resonance spectroscopy/mass spectrometry (HPLC/NMR/MS) experiment. This has been applied to a study of the metabolism of a model compound, 5-nitropyridone (2-hydroxy-5-nitropyridine), in maize plants grown hydroponically. By monitoring the on-flow reconstructed ion chromatogram corresponding to the 5-nitropyridone fragment at m/z 143, and additional molecular ions corresponding to metabolites identified as products from similar compounds, relevant peaks were identified rapidly for subsequent stopped-flow 1H NMR spectroscopic analysis. The combination of coupled HPLC/NMR/MS enabled the direct identification of three metabolites, namely the N-glucoside, N-malonylglucoside, and O-malonylglucoside. This work demonstrates the power of HPLC/NMR/MS for the structural elucidation of xenobiotic metabolites in complex biological matrices (such as plant material) with minimal sample preparation. In particular, using mass spectrometry for the initial identification of relevant HPLC peaks allows the analysis of complex samples without the necessity for other spectroscopic markers, such as 19F NMR signal for fluorinated compounds or UV spectroscopy for molecules with strong UV chromophores.     

尾式卟啉-5-氟尿嘧啶及其金属络合物的光谱分析

合成了24种新型的尾式卟啉-5-氟尿嘧啶化合物及其金属锰络合物,通过核磁共振氢谱（NMR）、质谱（MS）、红外光谱（IR）、紫外光谱（UV）及元素分析确定了其结构,并讨论了24种化合物光谱的关系特征及其规律,确定卟啉类配体与金属络合的NMR、IR、UV判据。     

Sterically demanding hetero-substituted [2]borametallocenophanes of group IV metals: synthesis, structure and reactivity

We report the synthesis and characterisation of unprecedented unstrained [2]diborametallocenophanes of zirconium and hafnium that bear the bulky octamethylfluorenyl (η(5)-C(29)H(36)) system, the proligands of which were pre-constructed by a two-step synthesis. The compounds were fully characterised by NMR spectroscopy, MALDI-TOF mass spectrometry and X-ray diffraction analysis. Typical reactivities relevant to olefin polymerisation such as methylation and chloride abstraction were also investigated. Finally, a sterically demanding bis(octamethylfluorenyl) metallocene was prepared.     

四(对烷氧苯基)卟啉及其金属络合物的光谱分析

利用IR、UV、1HNMR、MS、元素分析研究确证了38个卟啉类化合物及其金属络合物的结构。总结了卟啉类配体与金属络合的IR、UV、1HNMR判据。     

Guaiacol Substituted AzaPCs: A Novel Synthesis Method and Investigation of Photophysical Properties

AzaPCs containing tetra- and octaguaiacol moieties have not been investigated up to now. In this study, an unusual method is used for the synthesis of metalloAzaPCs (M: Zn, Co, Cu) containing guaiacol moieties. All compounds are characterized by a combination of FT-IR, ¹H NMR, ¹³C NMR, mass and UV/vis spectroscopy techniques. The molecular structure of starting pyrazine compounds 1 and 2 is also determined by the single crystal X-ray diffraction technique. The aggregation behavior of new Zn(II) AzaPCs is investigated in DMSO at different concentrations. The fluorescence properties of Zn(II) AzaPCs are investigated in different solvents. The fluorescence quantum yields of Zn(II) AzaPCs are calculated in DMSO.     

Perspectives in 1H, 14N and 81Br solid-state NMR studies of interfaces in materials textured by self-assembled amphiphiles

¹H solid-state NMR is becoming a routine characterisation tool. In the case of materials textured by self-assembled amphiphile molecules, we present a multi-scale characterisation approach, which can be easily implemented in most recent spectrometers. Valuable information on the interfaces between amphiphile molecules and oxide-based networks is obtained through this approach, as shown in some selected examples: block copolymers, hybrid siloxane membranes, and mesoporous microspheres obtained from spray-drying. We also present new results on ¹⁴N and ⁸¹Br solid-state NMR and discuss the applicability of direct or indirect proton-detected experiments to the study of mesoporous materials textured by cationic surfactants.     

Separation of xanthones and a biphenyl fromKielmeyera coriacea by centrifugal partition chromatography

Summary Eight xanthones and a biphenyl have been isolated from the dichloromethane extract ofKielmeyera coriacea (Guttiferae) stem bark by a combination of centrifugal partition chromatography and gel filtration on Sephadex LH-20, with HPLC-UV monitoring of fractions. The structures of the isolated compounds (Figure 1) were established by spectroscopic methods (UV, EI-MS, D/CI-MS,¹H NMR,¹³C NMR).     

Assessment of intercomponent interaction in phenylene bridged dinuclear ruthenium(II) and osmium(II) polypyridyl complexes

The synthesis and characterisation of [Ru(bipy)(2)(L1)](2+) and the homodinuclear complexes [M(bipy)(2)(L1)M(bipy)(2)](4+)(where M = Ru or Os), employing the ditopic ligand, 1,4-phenylene-bis(1-pyridin-2-ylimidazo[1,5-a]pyridine)(L1), are reported. The complexes are identified by elemental analysis, UV/Vis, emission, resonance Raman, transient resonance Raman and (1)H NMR spectroscopy, mass spectrometry and electrochemistry. The X-ray structure of the complex [Ru(bipy)(2)(L1)(bipy)(2)Ru](PF(6))(4) is also reported. DFT calculations, carried out to model the electronic properties of the compounds, are in good agreement with experiment. Minimal communication between the metal centres is observed. The low level of ground state electronic interaction is rationalized in terms of the poor ability of the phenyl spacer in facilitating superexchange interactions. Using the electronic and electrochemical data a detailed picture of the electronic properties of the RuRu compound is presented.     

Synthesis,characterization, crystal structures and antibacterial activities of some Schiff bases with N<Subscript>2</Subscript>O<Subscript>2</Subscript> donor sets

A series of Schiff base compounds were synthesized by the reaction of different 3,5-dihalosalicylaldehyde (halo atoms equal to Cl, Br and I) with polymethylenediamines of varying chain length. The Schiff bases were characterized using FT-IR, UV–Vis, ¹H NMR, ¹³C NMR and mass spectroscopic techniques, and elemental analyses (CHN), and crystal structure of some compounds was determined by X-ray crystallography. The in vitro biological screening effects of the synthesized compounds were tested against different microbial kinds. The results revealed that all compounds were biologically active.     

Synthesis of Some Bromomethyl‐ and (4‐Bromomethyl)phenyl‐Derivatives of 1,4,8,11 Tetraaza[14] annulene and Their Corresponding Sulfanylmethylene‐Derivatives Using 3‐Substituted Trimethinium Salts

Four new 6,13‐di(bromomethyl)‐ and di[(4‐bromomethyl)phenyl]1,4,8,11‐tetraaza[14]annulene derivatives C , D , E , F were synthesized using the condensation reaction of the correspondingly substituted vinamidinium salts with aromatic amines in acetonitrile/acetic acid. The reaction of these annulenes with thiourea leads to the corresponding thiol derivatives G and H . The UV/vis spectral behavior of compounds C , D , E , F , G , H was examined in DMSO. Elemental analysis, IR, ¹H‐NMR, ¹³C‐NMR, and mass spectral data confirm the molecular structure of the newly synthesized compounds.     

Synthesis and mesomorphism of tetrafluoro substituted 4-cyano oligophenyls

ABSTRACT

The synthesis and characterisation of new liquid crystal (LC) compounds based on terphenyl core are described. New family of dielectrically positive compounds presents alternative molecular approach to the conventional LC design. Correlations between molecular structure and mesomorphic properties for compounds being cyano terminated analogues as well as other known from the literature have been drawn. Compounds are characterised by ¹H NMR spectroscopy and mass spectrometry (electron ionisation) analysis. They show monotropic nematic behaviour in broad temperature range, confirmed by a polarising thermomicroscopy, differential scanning calorimetry. Detailed synthetic procedures are attached. Synthesised compounds stand as promising components of medium to highly birefringent liquid crystalline mixtures.     

Viscosalines B(1,2) and E(1,2): challenging new 3-alkyl pyridinium alkaloids from the marine sponge Haliclona viscosa

Four new 3-alkyl pyridinium alkaloids, the viscosalines?B(1) (1?a), B(2) (1?b), E(1) (2?a), and E(2) (2?b), were isolated from the Arctic sponge Haliclona viscosa. The structure elucidation of these isomeric compounds was challenging due to ambiguous fragments that derive during "standard" mass spectrometric fragmentation experiments. The final structure elucidation relied on the use of a combination of synthesis, liquid chromatography, and mass spectrometry. Three different mass spectrometers were used to differentiate between the synthetic structural isomers: a time-of-flight (TOF) mass spectrometer and two ion-trap mass spectrometers with different ion-transfer technologies (i.e., skimmer versus funnel optics). Although at first none of the spectrometers returned spectra that permitted structure elucidation, all three mass spectrometers provided analysis that successfully differentiated between the isomers after thorough method optimization. The use of in-source collision-induced dissociation (CID) with the ion trap and TOF instrument returned the most interesting results. The mode of fragmentation of the viscosalines under different experimental conditions is described herein. After successful optimization of the mass spectrometric method applied, the chromatographic method was improved to distinguish the previously inseparable isomers. Finally, both the liquid chromatography and mass spectrometric methods were applied to the natural products and the results compared to those from the synthetic compounds.     

Synthesis and properties of new non-symmetric 2,5-bis(4-alkylphenylethynyl)thiophenes

The synthesis and characterisation of new non-symmetric 2,5-bis(4-alkylphenylethynyl)thiophenes are described. Phase transition properties of these non-symmetric homologues are compared to those of the corresponding symmetric analogues. Furthermore, optical, dielectric and elastic data of investigated compounds and nematic mixture are provided. Compounds are characterised by ¹H NMR spectroscopy and mass spectrometry (electron ionization) analysis. They show an enantiotropic nematic behaviour in broad temperature ranges, confirmed by a polarising thermomicroscopy and differential scanning calorimetry. Detailed synthetic procedures are attached, showing a great synthetic versatility of the thiophene ring substitution. Synthesised compounds stand as promising components of highly birefringent liquid crystalline mixtures.     

Quantitative preparative gas chromatography of caffeine with nuclear magnetic resonance spectroscopy

Caffeine test solute was employed in combination with an internal standard (IS), 1,4‐dimethoxybenzene, in preparative‐gas chromatography (prep‐GC), with nuclear magnetic resonance (NMR) experiments. The IS served to: (i) quantify the trapping efficiency of an external trapping assembly, consisting of a capillary column cryotrap at the end of the analytical column; (ii) quantify the solute response in different NMR samples; and (iii) permit correlation of expected level of response of a compound in the NMR experiment, based on relative responses of the IS and solute in the GC result. The recovery rate of caffeine from multiple injections of sample (1×, 2×, 5× and 10×) was 69.6 ± 1.3%, which correlated well (R² = 0.999) with the number of injections of compound. The ¹H‐NMR spectrum was sufficient to enable structural characterisation of the reference caffeine compound, and was achieved with recovery of amounts of ≤10 μg from a single aliquot. Less than 400 μg of collected caffeine (40 replicate injections) was sufficient for structural characterisation by ¹³C‐NMR spectral analysis. The method allows development of approaches to separate unknown compounds in complex samples, and to separately use MS and NMR for their characterisation.     

Structural characterization of constituents with molecular diversity in fractions from Lysidice brevicalyx by liquid chromatography/diode-array detection/electrospray ionization tandem mass spectrometry and liquid chromatography/nuclear magnetic resonance

A combination of electrospray ionization tandem mass spectrometry with high-performance liquid chromatography (HPLC/ESI-MSn), and hyphenation of liquid chromatography to nuclear magnetic resonance spectroscopy (HPLC/NMR), have been extensively utilized for on-line analysis of natural products, analyzing metabolite and drug impurity. In our last paper, we reported an on-line analytical method for structural identification of trace alkaloids in the same class. However, the structural types of the constituents in plants were various, such as flavanoids, terpenoids and steroids. It is important to establish an effective analytical method for on-line structural identification of constituents with molecular diversity in extracts of plants. So, in the present study, the fragmentation patterns of some isolated stilbenes, phloroglucinols and flavanoids from Lysidice rhodostegia were investigated by ESI-MSn. Their fragmentation rules and UV characteristics are summarized, and the relationship between the spectral characteristics, rules and the structures is described. According to the fragmentation rules, NMR and UV spectral characteristics, 24 constituents of different types in the fractions from L. brevicalyx of the same genus were structurally characterized on the basis of HPLC/HRMS, HPLC-UV/ESI-MSn, HPLC/1H NMR and HPLC/1H-1H COSY rapidly. Of these, six (10, 13, 14, 16, 17 and 23) are new compounds and all of them are reported from L. brevicalyx for the first time. The aim is to develop an effective analytical method for on-line structural identification of natural products with molecular diversity in plants, and to guide the rapid and direct isolation of novel compounds by chemical screening.     

卤素取代甲苯的合成及其在Co(OAc)2－Mn(OAc)2－NaBr催化下的液相氧化反应

合成了3-氟甲苯和另外5个氯或溴取代的3-氟甲苯,以Co(OAc)₂·4H₂O、Mn(OAc)₂·4H₂O和NaBr为催化剂用液相氧化反应将其氧化为相应的卤代苯甲酸。该反应产率较高,所得卤代苯甲酸纯度好。6个卤代的3-氟甲苯及6个相应的卤代苯甲酸其结构经IR、UV、¹H NMR、MS和元素分析所确证。     

Viscosalines B1,2 and E1,2: Challenging New 3‐Alkyl Pyridinium Alkaloids from the Marine Sponge Haliclona viscosa

Four new 3‐alkyl pyridinium alkaloids, the viscosalines B₁ ( 1 a ), B₂ ( 1 b ), E₁ ( 2 a ), and E₂ ( 2 b ), were isolated from the Arctic sponge Haliclona viscosa. The structure elucidation of these isomeric compounds was challenging due to ambiguous fragments that derive during “standard” mass spectrometric fragmentation experiments. The final structure elucidation relied on the use of a combination of synthesis, liquid chromatography, and mass spectrometry. Three different mass spectrometers were used to differentiate between the synthetic structural isomers: a time‐of‐flight (TOF) mass spectrometer and two ion‐trap mass spectrometers with different ion‐transfer technologies (i.e., skimmer versus funnel optics). Although at first none of the spectrometers returned spectra that permitted structure elucidation, all three mass spectrometers provided analysis that successfully differentiated between the isomers after thorough method optimization. The use of in‐source collision‐induced dissociation (CID) with the ion trap and TOF instrument returned the most interesting results. The mode of fragmentation of the viscosalines under different experimental conditions is described herein. After successful optimization of the mass spectrometric method applied, the chromatographic method was improved to distinguish the previously inseparable isomers. Finally, both the liquid chromatography and mass spectrometric methods were applied to the natural products and the results compared to those from the synthetic compounds.