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Structural Characterisation (structural + characterisation)
Selected AbstractsExpanding the Range of "Daniphos"-Type P,P- and P,N-Ligands: Synthesis and Structural Characterisation of New [(,6 -arene)Cr(CO)3] ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2007Elisabetta Alberico Abstract New P,P- and P,N-ligands have been synthesised whose core structure is an [(,6 -arene)Cr(CO)3] unit. These new ligands, which extend the range of "Daniphos" ligands, are endowed with central and planar chirality and have been prepared through a stereoselective synthetic strategy from optically pure benzylamines bearing a second substituent on the arene other than the benzyldimethylamino group. Because the two faces of unsymmetrically 1,2- and 1,3-disubstituted benzylamine are diastereotopic, which means that diastereomeric complexes arise upon coordination of theCr(CO)3 fragment to either of these two faces, the synthetic plan has been adjusted by exploiting the trimethylsilyl group as a temporary steric modulator in order to access both complexes with high diastereoselectivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Structural Characterisation of Copper(II) 15-Metallacrown-5 Complexes with PbII, HgII, AgI, NaI and YIII Central Metal IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2007Sabry Hamed Seda Abstract The new copper(II) 15-metallacrown-5 complexes with the central metal ions PbII, HgII, AgI, NaI and YIII, with the formula [MCu5L5]Xn {H2L is 2-picolinehydroxamic acid or (S)-phenylalaninehydroxamic acid and X, is NO3, or Cl,}, have been synthesised and characterised by NMR and UV/Vis spectroscopy, electrospray mass spectrometry and elemental analysis. The PbII - and HgII 15-metallacrown-5 complexes were obtained in the crystalline form as pyridine adducts [PbCu5(picha)5(py)6](NO3)2·3(py) and [HgCu5(picha)5(py)7](NO3)2·2(py) and their X-ray crystal structures were determined. In both complexes, each peripheral CuII ion of the metallacrown is coordinated by one pyridine molecule bonded in the axial position. In the case of the PbII derivative, one additional axial pyridine molecule is bound to the central metal ion, while in the case of the HgII derivative, two axial pyridine ligands are bound to the central HgII ion. The relative stability of the copper(II) 15-metallacrown-5 complexes with various central metal ions was determined on the basis of competition reactions. The relative preference of the 15-metallacrown-5 system for the central metal ion follows the series NaI, AgI < lanthanide(III), HgII < PbII.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Structural Characterisation of Palladium and Group-12 Metal Complexes with a Hybrid Phosphanylphosphonate Ferrocene LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2006Abstract Diethyl [1,-(diphenylphosphanyl)ferrocenyl]phosphonate (1) was synthesised by stepwise metallation/functionalisation of 1,1,-dibromoferrocene and studied as a ligand for palladium(II) and group-12 metals. Treatment of [PdCl2(cod)] (cod = ,2:,2 -cycloocta-1,5-diene) with 1 in 1:1 or 1:2 molar ratios gave, respectively, the dinuclear, chloride-bridged complex [{Pd(,-Cl)Cl(1 -,P2)}2] (2) and the mononuclear complex trans -[PdCl2(1 -,P2)2] (3), where 1 coordinates exclusively through the phosphane function. The reactions between 1 and group-12 metal bromides MBr2 in a 1:1 molar ratio gave the adducts [MBr2(1)] [M = Zn (4), Cd (5), and Hg (6)], whose crystal structures change considerably with the metal ion. Thus, whereas 4 is a molecular complex with 1 coordinating as an O1,P2 -chelate, its cadmium(II) analogue is a polymer built up from symmetric {CdBr(,-Br)}2 units interconnected by pairs of O1,P2 -bridging phosphanylphosphonate ligands. Finally, the mercury(II) complex 6 is a halide-bridged dimer, [{Hg(,-Br)Br(1 -,P2)}2]. However, this compound is structurally fluxional in solution (NMR spectra) and, in the crystal, it attains a structure similar to 5 owing to weak interactions between mercury and phosphonate-O1 atoms from adjacent molecules. An isomer to 6, [{HgBr2(1 -,2O1,P2)}2] (7), was isolated from attempted alkylation of 6 and structurally characterised as a dimer, where ligands 1 bridge two {HgBr2} units. All compounds were studied by spectroscopic methods (IR, NMR, mass) and the solid-state structures of 1, 2·,H2O, 3·4,CHCl3, 4, 5, 6·5,C6H6, and 7 have been determined by single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis, Structural Characterisation and Reactions of Some Vinylgold(I) Phosphane ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Fabian Mohr Abstract A series of vinylgold(I) complexes [Au(CR=CHR)L] (R = H, Me; L = PPh3, PPh2Me, PPhMe2) were prepared from the reaction of the Grignard reagents [MgBr(CR=CHR)] (R = H, Me) with the gold(I) phosphane complexes [AuCl(L)] (L = PPh3, PPh2Me, PPhMe2) at low temperature. The complexes were characterised by various spectroscopic techniques and, in the case of [Au(CMe=CHMe)(PPh3)], by a single-crystal X-ray structure determination. The gold,carbon bonds of these vinylgold(I) complexes are easily cleaved by acids and, in the presence of potassium permanganate, by species containing acidic protons. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] endo and exo Coordination of Indanol: Synthesis, Isolation and Structural Characterisation of [H3Ru3(endo -Indanol)(C6Me6)2(O)]+ and [H3Ru3(exo -Indanol)(C6Me6)2(O)]+ as Their Tetrafluoroborate SaltsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2004Ludovic Vieille-Petit Abstract The reaction of 2,3,4,7-tetrahydro-1H -inden-2-ol with ruthenium chloride hydrate in refluxing ethanol yields the chloro-bridged dinuclear complex [RuCl2(indanol)]2 (1). The mononuclear complex [Ru(indanol)(H2O)3]2+ (2), formed in situ from 1 in aqueous solution, reacts with the dinuclear complex [H3Ru2(C6Me6)2]+ to give a trinuclear arene-ruthenium cluster as a mixture of two isomers, the cations [H3Ru3(endo -indanol)(C6Me6)2(O)]+ (3a) and [H3Ru3(exo -indanol)(C6Me6)2(O)]+ (3b), in a 1:1 ratio. The hydroxy function of the indanol ligand is oriented towards the ,3 -oxo cap of 3a, whereas the OH group is bent away from the metal skeleton of 3b. These two isomers, which can easily be separated by silica-gel chromatography, were isolated and characterised as their tetrafluoroborate salts. The single-crystal X-ray structure analysis of [3a][BF4] shows a strong intramolecular hydrogen bond between the ,3 -oxo ligand and the hydroxyl function, which even persists in acetone solution, as demonstrated by NMR spectroscopy. On the other hand, the hydroxy function of 3b was found to be free in the solid state as well as in solution, as shown by an X-ray crystal structure analysis and by NMR spectroscopy. The catalytic activities of the water-soluble trinuclear cations 3a and 3b for the hydrogenation of benzene to give cyclohexane under biphasic conditions are considerably different, the exo isomer 3b being more active than the endo isomer 3a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Lignin Chemistry: Biosynthetic Study and Structural Characterisation of Coniferyl Alcohol Oligomers Formed In Vitro in a Micellar EnvironmentCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2010Samantha Reale Dr. Abstract Model coniferyl alcohol lignin (the so-called dehydrogenative polymerisate, DHP) was produced in water under homogeneous conditions guaranteed by the presence of a micellised cationic surfactant. A complete study of the activity of the enzymatic system peroxidase/H2O2 under our reaction conditions was reported and all the reaction products up to the pentamer were characterised by 1H,NMR spectroscopy and ESI mass spectrometry. Our system, and the molecules that have been generated in it, represent a closer mimicry of the natural microenvironment since an enzyme, under micellar conditions, reproduces the cell system better than in buffer alone. On the basis of the oligomers structures a new biosynthetic perspective was proposed that focused attention on a coniferyl alcohol dimeric quinone methide as the key intermediate of the reaction. A formal, strictly alternate sequence of a radical and an ionic step underlines the reaction, thus generating ordered oligolignols structures. Alternatively to other model lignins, our olignols present a lower degree of radical coupling between oligomeric units. This offers a closer biosynthetic situation to the observation of a low rate of radical generation in the cell wall. [source] Structural and Magnetic Resolution of a Two-Step Full Spin-Crossover Transition in a Dinuclear Iron(II) Pyridyl-Bridged CompoundCHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2006Jarrod J. M. Amoore Abstract A dinuclear iron(II) complex containing the new pyridyl bridging ligand, 2,5-di(2,,2,,-dipyridylamino)pyridine (ddpp) has been synthesised and characterised by single-crystal X-ray diffraction, magnetic susceptibility and Mössbauer spectral methods. This compound, [Fe2(ddpp)2(NCS)4],4,CH2Cl2, undergoes a two-step full spin crossover. Structural analysis at each of the three plateau temperatures has revealed a dinuclear molecule with spin states HS,HS, HS,LS and LS,LS (HS: high spin, LS: low spin) for the two iron(II) centres. This is the first time that resolution of the metal centres in a HS,LS ordered state has been achieved in a two-step dinuclear iron(II) spin-crossover compound. Thermogravimetric data show that the dichloromethane solvate molecules can be removed in two distinct steps at 120,°C and 200,°C. The partially de-solvated clathrate, [Fe2(ddpp)2(NCS)4],CH2Cl2, undergoes a one-step transition with an increased transition temperature with respect to the as synthesised material. Structural characterisation of this material reveals subtle changes to the coordination geometries at each of the iron(II) centres and striking changes to the local environment of the dinuclear complex. The fully de-solvated material remains high spin over all temperatures. Interestingly, the solvent can be re-introduced into the monosolvated solid to achieve complete conversion back to the original two-step crossover material, [Fe2(ddpp)2(NCS)4],4,CH2Cl2. [source] A combined HPLC-UV and HPLC-MS method for the identification of lignans and its application to the lignans of Linum usitatissimum L. and L. bienne Mill.,PHYTOCHEMICAL ANALYSIS, Issue 5 2006Thomas J. Schmidt Abstract A combined HPLC-UV/PAD and HPLC-ESI/MS method allowing the fast detection and identification/structural characterisation of lignans of different structural subclasses is described. Twenty-four lignans of different skeletal types were analysed and the combined information derived from their UV and ESI/MS spectra led to the identification of group characteristics that can be used to establish the structure of unknown lignans in plant samples. This method was successfully applied to the identification of lignans in crude extracts of Linum usitatissimum L. and L. bienne Mill. Copyright © 2006 John Wiley & Sons, Ltd. [source] Synthesis and Characterisation of Novel Complexes Containing Group 15 Elements and Their Potential Use as Molecular Precursors for the Formation of Transition Metal PnictidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2005Manfred Scheer Abstract The reaction of [{W(CO)5}2PCl] with K[Co(CO)4] yields the novel compounds [{W(CO)4Co2(CO)6}{µ3 -PW(CO)5}2] (3) and [{(CO)4WCo3(CO)6}{µ3 -PW(CO)5}3] (4) along with known derivatives [Co2(CO)6{,,,2 -PW(CO)5}2] (1) and [Co3(CO)9{,3 -PW(CO)5}] (2). The complex [{W2(CO)8(,-CO)}{,,,2:,1:,1 -PW(CO)5}2)] (5) was synthesised by treating Na2[W2(CO)10] with PBr3. Reaction of K[Mn(CO)5] with SbCl3 affords [Sb{Mn(CO)5}3] (6) in high yields. The spectroscopic and structural characterisation of the novel products is discussed, as well as the thermolytic behaviour of 2, 3 and 6 for the potential formation of novel phases of transition metal pnictides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Polytype control and properties of AlN on siliconPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005V. Cimalla Abstract In this paper we report on the optical and structural characterisation of cubic polytype AlN thin films on 3C-SiC/Si(111) pseudo-substrates prepared by carbonisation. We have found that 3C-AlN phase can be stabilised on the "waved" 3C-SiC(111) surface by polytype replication. On the other hand, 2H-AlN was grown on atomically smooth surfaces. X-ray diffraction and transmission electron microscopy imply that the cubic AlN was grown along with hexagonal inclusions up to 20%. Spectroscopic ellipsometry in the infrared region show the typical phonon lines for the two polytypes. The appearance of the TO phonon at 646 cm,1 confirms the existence of 3C-AlN. In the ultraviolet region the critical points in the band structure were identified. For 3C- and 2H-AlN the first direct transition at the ,-point was determined to be at 5.74 eV and 6.16 eV, respectively. No indirect transition at lower energies was detected. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phenolic compounds in the brown seaweed Ascophyllum nodosum: distribution and radical-scavenging activitiesPHYTOCHEMICAL ANALYSIS, Issue 5 2010Laetitia Audibert Abstract Introduction , Phenolic compounds are metabolites exhibited at high levels in Phaeophyceae. Although several studies have been conducted on total phenol contents, no one to our knowledge has dealt with the contents of phenolic compounds and antioxidant activities on purified fractions. Objective , The purpose of this study was the extraction and purification of phenolic compounds from the brown seaweed Ascophylllum nodosum, to determine both their distribution and their radical-scavenging activities, and to obtain a sufficiently purified oligophenolic fraction to perform an RP-HPLC analysis on molecules with a molecular weight (MW) < 2,kDa. Methodology , Phenolic compounds were separated and purified by liquid,liquid extraction, tangential ultrafiltration and dialysis. Then, the contents of both phenolic compounds and radical-scavenging activities were measured by the Folin,Ciocalteu reagent, and DPPH and ABTS assays. NMR analysis was performed to validate the process. RP-HPLC with a C18 column was performed on the oligophenolic fraction, using a novel method developed in this study. Results , Seven fractions were obtained as a function of polarity and molecular weight. Among them, the fraction containing phenolic compounds with a MW , 50,kDa appeared to be the most active, correlated with the content of phenolic compounds. Conclusion , This work constitutes a step forward in the separation and purification of bioactive phlorotannins and represents a prerequisite for further investigations into their structural characterisation and distribution in A. nodosum. [source] Analysis of sesterterpenoids from Aspergillus terreus using ESI-QTOF and ESI-ITPHYTOCHEMICAL ANALYSIS, Issue 4 2010Zhi-Jun Wu Abstract Introduction , Biosynthesis of terretonin was studied due to the interesting skeleton of this series of sesterterpenoids. Very recently, López-Gresa reported two new sesterterpenoids (terretonins E and F) which are inhibitors of the mammalian mitochondrial respiratory chain. Mass spectrometry (MS), especially tandem mass spectrometry, has been one of the most important physicochemical methods for the identification of trace natural products due to it rapidity, sensitivity and low levels of sample consumption. The potential application prospect and unique skeleton prompted us to study structural characterisation using MS. Objective , To obtain sufficient information for rapid structural elucidation of this class of compounds using MS. Methodology , The elemental composition of the product ions was confirmed by low-energy ESI-CID-QTOF-MS/MS analyses. The fragmentation pathways were postulated on the basis of ESI-QTOF-MS/MS/MS and ESI-IT-MSn spectra. Common features and major differences between ESI-QTOF-MS/MS and IT-MSn spectra were compared. For ESI-QTOF-MS/MS/MS experiments, capillary exit voltage was raised to induce in-source dissociation. Ammonium acetate or acetic acid were added into solutions to improve the intensity of [M + H]+. The collision energy was optimised to achieve sufficient fragmentation. Some fragmentation pathways were unambiguously proposed by the variety of abundance of fragment ions at different collision energies even without MSn spectra. Results , Fragmentation pathways of five representative sesterterpenoids were elucidated using ESI-QTOF-MS/MS/MS and ESI-IT-MSn in both positive- and negative-ion mode. The key group of characterising fragmentation profiles was ring B, and these fragmentation patterns are helpful to identify different types of sestertepenoids. Conclusion , Complementary information obtained from fragmentation experiments of [M + H]+ (or [M + NH4]+) and [M , H], precursor ions is especially valuable for rapid identification of this kind of sesterterpenoid. [source] Determining the topology of virus assembly intermediates using ion mobility spectrometry,mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2010Tom W. Knapman We have combined ion mobility spectrometry,mass spectrometry with tandem mass spectrometry to characterise large, non-covalently bound macromolecular complexes in terms of mass, shape (cross-sectional area) and stability (dissociation) in a single experiment. The results indicate that the quaternary architecture of a complex influences its residual shape following removal of a single subunit by collision-induced dissociation tandem mass spectrometry. Complexes whose subunits are bound to several neighbouring subunits to create a ring-like three-dimensional (3D) architecture undergo significant collapse upon dissociation. In contrast, subunits which have only a single neighbouring subunit within a complex retain much of their original shape upon complex dissociation. Specifically, we have determined the architecture of two transient, on-pathway intermediates observed during in vitro viral capsid assembly. Knowledge of the mass, stoichiometry and cross-sectional area of each viral assembly intermediate allowed us to model a range of potential structures based on the known X-ray structure of the coat protein building blocks. Comparing the cross-sectional areas of these potential architectures before and after dissociation provided tangible evidence for the assignment of the topologies of the complexes, which have been found to encompass both the 3-fold and the 5-fold symmetry axes of the final icosahedral viral shell. Such insights provide unique information about virus assembly pathways that could allow the design of anti-viral therapeutics directed at the assembly step. This methodology can be readily applied to the structural characterisation of many other non-covalently bound macromolecular complexes and their assembly pathways. Copyright © 2010 John Wiley & Sons, Ltd. [source] Liquid chromatography coupled to quadruple time-of-flight tandem mass spectrometry for microcystin analysis in freshwaters: method performances and characterisation of a novel variant of microcystin-RRRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2009Pasquale Ferranti Cyanobacteria, also called blue-green algae, occur worldwide within water blooms in eutrophic lakes and drinking water reservoirs, producing several biotoxins (cyanotoxins). Among these, microcystins (MCs) are a group of cyclic heptapeptides showing potent hepatotoxicity and activity as tumour promoters. So far, at least 89 MCs from different cyanobacteria genera have been characterised. Herein, ion trap, matrix-assisted laser desorption/ionisation time-of-flight (MALDI-ToF) and quadruple time-of-flight (Q-ToF) mass spectrometry (MS)-based methods were tested and compared for analysing MCs in freshwaters. Method performances in terms of limit of detection, limit of quantification, mean recoveries, repeatability, and specificity were evaluated. In particular, a liquid chromatography/electrospray ionisation (LC/ESI)-Q-ToF-MS/MS method was firstly described to analyse MCs in freshwaters; this technique is highly selective and sensitive, and allowed us to characterise the molecular structure of an unknown compound. Indeed, the full structural characterisation of a novel microcystin variant from a bloom of Planktothrixrubescens in the Lake Averno, near Naples, was attained by the study of the fragmentation pattern. The new cyanotoxin was identified as the 9-acetyl-Adda variant of microcystin-RR. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ion trap mass spectrometry in the structural analysis of haemoglobin peptides modified by epichlorohydrin and diepoxybutaneRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2002Nadia Miraglia Ion trap mass spectrometry has been shown to be particularly suitable for the structural analysis of high molecular weight peptides directly fragmented in the mass analyser without needing further sub-digestion reactions. Here we report the advantages of using multi-stage ion trap mass spectrometry in the structural characterisation of haemoglobin alkylated with epichlorohydrin and diepoxybutane. Alkylated globins were digested with trypsin and the peptide mixtures were analysed by MS3. This technique allows the sequential fragmentation of peptides under analysis, giving rise to MS3 product ion spectra with additional information with respect to MS2 mass spectra. The results obtained complete the previously reported structural characterisation of alkylated haemoglobin, demonstrating the potential of ion trap mass spectrometry. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||