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Spectroscopic Methods (spectroscopic + methods)
Kinds of Spectroscopic Methods Selected AbstractsANALYSIS OF NASRID POLYCHROME CARPENTRY AT THE HALL OF THE MEXUAR PALACE, ALHAMBRA COMPLEX (GRANADA, SPAIN), COMBINING MICROSCOPIC, CHROMATOGRAPHIC AND SPECTROSCOPIC METHODS,ARCHAEOMETRY, Issue 4 2009C. CARDELL The pigments, binders and execution techniques used by the Nasrids (1238,1492) to polychrome carpentry in the Hall of the Mexuar Palace at the Alhambra (Granada, Spain) were studied using optical microscopy, scanning electron microscopy with EDX analysis, selective staining techniques and gas chromatography , mass spectrometry. This pioneering investigation presents the first results of a research project devoted to filling gaps in the knowledge of Nasrid art, traditionally approached by stylistic studies. Moreover, it is essential for the polychromy conservation of the studied artworks, and will help to clarify historical and painting uncertainties in the Alhambra monument. The palette consists of a limited range of colours: white (lead-base pigment), red (cinnabar and red lead), blue (lapis lazuli), black (carbon-based) and false gold (golden tin). Tempera grassa was the painting technique identified. Two types of grounds were used: (i) gypsum in calligraphy decoration for the false gold technique, and (ii) synthetic minium in geometric drawings in carpentry. Organic insulating layers of linseed oil were used between paint strata. Artists applied synthetic minium to protect the wood (Juglans regia and conifer) against attack by xylophages. To lighten the surface darkened by this ground layer, powdered tin was added to achieve a metallic lustre. [source] Study of Factors Affecting Molecular Behaviors in Phenothiazine-Mediated Biosensing by Electrochemical and Spectroscopic MethodsELECTROANALYSIS, Issue 23 2006Yetunde Abstract Reagentless glucose-detecting biosensors were constructed by incorporating a series of phenothiazine derivatives as mediators onto chitosan (CHIT) matrix via different covalent bonds, wherein glucose oxidase (GOx) was employed as the enzyme. Electrochemical studies show significant decrease in the electrocatalytic current during cyclic voltammetric and amperometric measurements, resulting from complexes formation between GOx and phenothiazine molecules. This behavior was further verified by spectroscopic studies. The decrease in the peak intensity at 258,nm is due to the gradual complexes formation over time, consistent to the decrease in the current signal in electrochemical investigations. Correlation with the molecular structures of phenothiazine derivatives reveals a strong relationship between the hydrophobicity of the mediators and the stability of the biosensor electrodes. [source] Evaluation of the Photodegradation of Crystal Violet upon Light Exposure by Mass Spectrometric and Spectroscopic MethodsJOURNAL OF FORENSIC SCIENCES, Issue 2 2009Céline Weyermann Dr. rer. nat. Abstract:, Crystal violet is a very common dye in ballpoint ink. Recent research suggests that the degradation of triarylmethane dyes gives an indication of the age of a ballpoint pen entry on a document. The main problem for the quantitative evaluation of the degradation is that it is highly dependent on the exposure to light. Moreover additional factors, such as additives and substrate play an important role in this process. The aim of this work is to compare the degradation pathways of the pure dye in water and ethanol upon exposure to xenon light by UV/VIS spectrophotometry and laser desorption ionization. Significant differences have been observed in the products and the kinetics of the degradation. N-demethylation, an expected decomposition process, was found to take place only in aqueous solution and kinetics calculations showed that the degradation occurred 2.5 times faster in ethanol compared to water. The degradation of crystal violet in inks from four ballpoint pens on paper was also studied for entries made over 2,3 years. It was observed that degradation reactions were quenched by the presence of another dye due to competitive absorption. It was also observed that the thickness of a stroke (concentration of ink) influenced the degradation process. In the absence of light only one ballpoint pen showed slight degradation. A better understanding of the influence of the paper, ink composition, and storage conditions is necessary to interpret correctly the age of an ink based on the degradation of dyes. [source] Investigations on the Photoinitiator-free Photopolymerization of Acrylates by Vibrational Spectroscopic MethodsMACROMOLECULAR SYMPOSIA, Issue 1 2005Tom Scherzer Abstract Photopolymerization of acrylates without photoinitiators was carried out by irradiation with short-wavelength UV light from excimer lamps with an emission at 222 or 172 nm. Basic investigations on the reactivity of various acrylates and on the conditions under which they can be UV-cured were performed by real-time FTIR-ATR spectroscopy. Depending on the molar extinction coefficients of a specific acrylate at the wavelength of irradiation, the absorption of the light within the coating leads to a pronounced intensity gradient which significantly influences polymerization rate and conversion. Accordingly, it limits the maximum thickness of the layer that can be cured (ranging from some hundreds of nanometres up to some micrometers). In addition to the basic studies, thin acrylate coatings were also cured on pilot scale. The actual conversion in the layer after UV irradiation was directly monitored by in-line NIR reflection spectroscopy, and the resulting coatings were characterized by FTIR spectroscopy and hardness measurements. [source] In vivo spectroscopy in dermatology: methods and new fields of applicationJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 1 2000K Liebold Abstract Background,The human skin is an easily accessible organ on which non-invasive examination methods can be applied. Remittance spectroscopy uses registration of the proportion of reflected light from the skin surface. Optical characteristics of skin are determined by scattering, reflection and absorption. The remittance is influenced by various test conditions and topography. Spectroscopic methods are applied for determination of microcirculation, measuring of erythema and pigmentation and in pharmacology and toxicology of applied drugs. Conclusion,The standardization of spectroscopic measurement of human skin is essential to reduce error sources. In future a better investigation of skin structures and molecules, which are responsible for optical characteristics of skin and a more precise evaluation of spectroscopic signals are necessary to get more information about the state of skin and to develop new fields of applications, such as early diagnosis of skin diseases or monitoring of metabolic processes. [source] Voltammetric Analysis of Trace Levels of Platinum Group Metals , Principles and ApplicationsELECTROANALYSIS, Issue 21 20072Article first published online: 4 OCT 200, Clinio Locatelli Abstract The compelling use of autocatalytic converters, containing platinum group metals (PGMs), has been the cause, in the environmental and biological matrices, of an increasing concentration of such metals. For this reason, in the last decade, the literature has reported several papers regarding analytical procedures for the determination of Pt(II), Pd(II) and Rh(III) in real samples, generally employing spectroscopic methods. The present review intends to highlight the contribution of the voltammetric techniques for the determination of these metals, including also those less investigated, i.e. Iridium, Osmium and Ruthenium. [source] Production of Taxol fromPhyllosticta spinarum, an endophytic fungus ofCupressus sp.ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2008R. Senthil Kumaran Abstract Taxol production during the cultivation on a modified liquid and potato dextrose broth medium was indicated for the first time to occur in Phyllosticta spinarum, an endophytic fungus isolated from the needles of Cupressus sp. The presence of taxol in the fungal culture filtrate was confirmed by chromatographic and spectroscopic methods of analysis. The amount of taxol produced by this fungus was quantified by high performance liquid chromatography. The maximum amount of taxol production was obtained in this fungus when grown on M1D medium (235,,g/L) followed by PDB medium (125,,g/L). The results indicate that P.,spinarum is an excellent candidate for taxol production. The production rate was 4.7,×,103 -fold higher than that found in the culture broth of an earlier reported fungus, Taxomyces andreanae. The fungal taxol extracted also showed a strong cytotoxic activity in the in vitro culture of human cancer cells tested in an apoptotic assay. [source] Tricarbonyl Rhenium(I) and Technetium(I) Complexes with Hydrazones Derived from 4,5-Diazafluoren-9-one and 1,10-Phenanthroline-5,6-dioneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010Paula Barbazán Abstract Tricarbonylrhenium(I) and -technetium(I) halide (halide = Cl and Br) complexes of ligands derived from 4,5-diazafluoren-9-one (df) and 1,10-phenanthroline-5,6-dione (phen) derivatives of benzoic and 2-hydroxybenzoic acid hydrazides have been prepared. The complexes have been characterized by elemental analysis, MS, IR, 1H NMR and absorption and emission UV/Vis spectroscopic methods. The metal centres (ReI and TcI) are coordinated through the nitrogen imine atoms and establish five-membered chelate rings, whereas the hydrazone groups stand uncoordinated. The 1H NMR spectra suggest the same behaviour in solution on the basis of only marginal variations in the chemical shifts of the hydrazine protons. [source] Heteroleptic Guanidinate- and Amidinate-Based Complexes of Hafnium as New Precursors for MOCVD of HfO2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Ke Xu Abstract The synthesis and characterization of four new heteroleptic complexes [Hf{,2 -(iPrN)2CNMe2}2Cl2] (1), [Hf{,2 -(iPrN)2CNMe2}2Me2] (2), [Hf{,2 -(iPrN)2CMe}2Cl2] (3), and [Hf{,2 -(iPrN)2CMe}2Me2] (4) are reported. All the complexes were characterized by spectroscopic methods, while compounds 1,3 were further examined by single-crystal X-ray diffraction, revealing that the complexes are monomers with the hafnium center in a distorted octahedral geometry. The thermal properties of the chlorine-free complexes (2, 4) were examined to determine their suitability for metalorganic chemical vapor deposition (MOCVD) applications, and compound 2 showed good volatility and thermal stability. On the basis of these results, compound 2 was selected for MOCVD of HfO2 with oxygen as oxidant. Depositions were carried out on Si(100) substrates in the temperature range 300,700 °C. The as-deposited HfO2 films crystallized in the monoclinic phase at temperatures above 500 °C, and the composition analysis determined by Rutherford back-scattering (RBS) and X-ray photoelectron spectroscopy (XPS) revealed that the films were stoichiometric and free of carbon. Thus, alkylguanidinatohafnium complex 2 is a promising precursor for growing HfO2 films in a wide temperature range with the desired stoichiometry, because of its adequate volatility, sufficient temperature window between vaporization and decomposition, as well as its ability to decompose cleanly in the presence of oxygen. [source] Synthesis, Characterization and OFET Properties of Amphiphilic Mixed (Phthalocyaninato)(porphyrinato)europium(III) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2009Pan Ma Abstract Amphiphilic mixed (phthalocyaninato)(porphyrinato)europium(III) triple-decker complexes Eu2[Pc(15C5)4]2[T(C10H21)4P] (1) and Eu2[Pc(15C5)4]2[TPOPP] (2) [H2Pc(15C5)4 = 2,3,9,10,16,17,23,24-tetrakis(15-crown-5)phthalocyanine; H2T(C10H21)4P = meso -5,10,15,20-tetra- n -decylporphyrin, H2TPOPP = meso -5,10,15,20-tetrakis(4-pentyloxyphenyl)porphyrin] were designed and synthesized by the raise-by-one-story method. These novel sandwich triple-decker complexes were characterized by a wide range of spectroscopic methods, and they were also electrochemically studied. Highly ordered films were fabricated by the Langmuir,Blodgett (LB) technique into organic field-effect transistors (OFETs). The devices display good OFET performance with a carrier mobility in the range 0.03,0.78 cm2,V,1,s,1. As expected, the devices show a low threshold voltage range from ,1.19 to ,4.34 V. The mobility of compound 1 reaches 0.78 cm2,V,1,s,1, which is the highest value so far achieved for LB film-based OFETs, as a result of the narrow energy gap (1.04 eV) of this compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Valence-Tautomeric RbMnFe Prussian Blue Analogues: Composition and Time Stability InvestigationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2009Lionel Salmon Abstract Three different stoichiometric forms of RbxMn[Fe(CN)6]y·zH2O [x = 0.96, y = 0.98, z = 0.75 (1); x = 0.94, y = 0.88, z = 2.17 (2); x = 0.61, y = 0.86, z = 2.71 (3)] Prussian blue analogues were synthesized and investigated by magnetic, calorimetric, Raman spectroscopic, X-ray diffraction, and 57Fe Mössbauer spectroscopic methods. Compounds 1 and 2 show a hysteresis loop between the high-temperature (HT) FeIII(S = 1/2),CN,MnII(S = 5/2) and the low-temperature (LT) FeII(S = 0),CN,MnIII(S = 2) forms of 61 and 135 K width centered at 273 and 215 K, respectively, whereas the third compound remains in the HT phase down to 5 K. The splitting of the quadrupolar doublets in the 57Fe Mössbauer spectra reveal the electron-transfer-active centers. Refinement of the X-ray powder diffraction profiles shows that electron-transfer-active materials have the majority of the Rb ions on only one of the two possible interstitial sites, whereas nonelectron-transfer-active materials have the Rb ions equally distributed. Moreover, the stability of the compounds with time and following heat treatment is also discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Monocyclopentadienyl Phenoxido,Amino and Phenoxido,Amido Titanium Complexes: Synthesis, Characterisation, and Reactivity of Asymmetric Metal Centre DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2008Giuseppe Alesso Abstract Reduction of phenol,imine derivatives R,N=CH(3,5-R2C6H2 -2-OH) (R = tBu; R, = C6H51a, p -MeC6H41b, Cy 1c, tBu 1d, 2,6-Me2C6H31e; R = H; R, = p -MeC6H41f; Cy = cyclohexyl) with MBH4 (M = Li, Na) or AlLiH4 in ethyl ether or thf at room temperature affords the phenol,amine compounds R,NHCH2(3,5-R2C6H2 -2-OH) 2a,c and 2e,f. The N -R-[2,4-di- tert -butyl]benzo-1-oxa-3-azine species (R = tBu 2d1, 2,6-Me2C6H32e1) are obtained by Mannich reaction of 2,4-di- tert -butylphenol with RNH2 in refluxing methanol. Intermediate 2d1 is converted in ethanol at room temperature into N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylamine (2d), whereas 2e is not obtained from 2e1 by using this procedure.N -alkyl,N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylaminecompounds tBuN(R)CH2(3,5- tBu2C6H2 -2-OH) (R = Me 2g, Et 2h, nPr 2i, CH2Ph 2j) are also prepared by the appropriate synthetic method. Treatment of 2a,c with 1 equiv. of TiCpCl3 in the presence of 2.5 equiv. of NEt3 in hexane at room temperature gives the monocyclopentadienyl phenoxido,amido monochloride complexes TiCp[R,NCH2(3,5- tBu2C6H2 -2-O)]Cl (R, = C6H53a, R, = p -MeC6H43b, R, = Cy 3c). The analogous complex Ti(,5 -C5H4SiMe2Cl)[C6H5NCH2(3,5- tBu2C6H2 -2-O)]Cl (4a) results from the reaction of 2a with Ti(,5 -C5H4SiMe2Cl)Cl3. Nevertheless, 2d reacts with TiCpCl3 in hexane in the presence of NEt3 at room temperature yielding the monocyclopentadienyl phenoxido dichloride compound TiCp[tBuNHCH2(3,5- tBu2C6H2 -2-O)]Cl2 (5), whereas in ethyl ether and in the absence of NEt3 adduct 5·HCl is obtained, which is further converted into TiCp[tBuNCH2(3,5- tBu2C6H2 -2-O)]Cl (3d) by addition of a NEt3/ethyl ether solution. The reaction of TiCpCl3 with 2a in the presence of 2.5 equiv. of NEt3 in a polar solvent (thf, CH2Cl2 or toluene) at room temperature affords TiCp[Ph(H)NCH2(3,5- tBu2C6H2 -2-O)]Cl (6a) as a mixture of two stereoisomers. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2a, 2d, 2e and 3d were determined by X-ray diffraction analysis from suitable single crystals. Preliminary studies of catalytic activity for ethylene polymerisation by using solid methylaluminoxane as cocatalyst were performed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis, Coordination and Catalytic Utility of Novel Phosphanyl,ferrocenecarboxylic Ligands Combining Planar and Central ChiralityEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Martin Lama Abstract The chiral ferrocene derivative (R,Rp)-2-[1-(diphenylphosphanyl)ethyl]ferrocenecarboxylic acid (1) is prepared together with selected derivatives resulting from modification at the phosphane moiety [P -oxide (5) and P -sulfide (4)] and the carboxyl group {amides bearing benzyl (6) and (R)- or (S)-1-phenylethyl substituents [(R)- 7 and (S)- 7] at the amide nitrogen atom}. Acid 1 and amide 6 are studied as ligands in rhodium and palladium complexes. Bridge cleavage of the dimer [{Rh(,-Cl)Cl(,5 -C5Me5)}2] with 1 gives [RhCl2(,5 -C5Me5)(1 -,P)] (9) containing P-monodentate 1, which undergoes smooth conversion to the (phosphanylalkyl)ferrocenecarboxylato complex [RhCl(,5 -C5Me5){Fe(,5 -C5H5)(,5 -C5H3 -1-CH(Me)PPh2 -2-COO-,2O,P}] (10) upon treatment with silica gel or alumina. Yet another O,P -chelate complex,[Rh{Fe(,5 -C5H5)(,5 -C5H3 -1-CH(Me)PPh2 -2-COO-,2O,P}(CO)(PCy3)] (11; Cy = cyclohexyl) is obtained directly by an acid-base reaction between the acetylacetonato complex [Rh(acac)(CO)(PCy3)] and 1. Amide 6 reacts with [{Pd(,-Cl)(,3 -C3H5)}2] to give the expected phosphane complex [PdCl(,3 -C3H5)(6 -,P)] (12), while the replacement of the cyclooctadiene (cod) ligand in [PdCl(Me)(cod)] affords the chelate complex [PdCl(Me)(6 -,2O,P)] (13). All compounds are characterised by spectroscopic methods and the solid-state structures of 5, 9, 11, 13, (R,Sp)-2-[1-(diphenylphosphoryl)ethyl]-1-[N -(R)-(1-phenylethyl)carbamoyl]ferrocene [(R)- 8; phosphane oxide from (R)- 7], and the synthetic precursors (R,Sp)-1-bromo-2-[1-(diphenylphosphanyl)ethyl]ferrocene (2) and (R,Sp)-1-bromo-2-[1-(diphenylthiophosphoryl)ethyl]ferrocene (3) determined by single-crystal X-ray diffraction. The catalytic properties of 1 and the amides are probed in enanatioselective rhodium-catalysed hydrogenation and palladium-catalysed asymmetric allylic alkylation. (© 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] Preparation of Diamidochloro(cyclopentadienyl)titanium Derivatives as Pre-Catalysts for Olefin Polymerization , X-ray Molecular Structure of [Ti(,5 -C5H5){1,2-C6H4(NCH2CH2CH3)2}Cl] and [Ti{,5 -C5H4(SiMe3)}{1,2-C6H4(NCH2CH2CH3)2}Cl]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2004Vanessa Tabernero Abstract The synthesis of N,N,-alkyl 1,2-phenylenediamines 1,2-C6H4(NHR)2 [R = CH2CH2CH3 (nPr), CH2tBu (Np)] was carried out in three steps by lithiation of the primary 1,2-phenylenediamine, reaction with the appropriate acyl chloride and reduction with LiAlH4. The addition of nBuLi to a stirred solution of N,N,-alkyl diamines in cold hexane resulted in the immediate deposition of the corresponding lithium salts, which react with [MCpR,Cl3] to give the diamidochloro(,5 -cyclopentadienyl)titanium and -zirconium complexes [MCpR,{1,2-C6H4(NR)2}Cl] (4,10) [M = Ti, Zr; CpR, = ,5 -C5H5, ,5 -C5(CH3)5, ,5 -C5H4(SiMe3); R = nPr, Np]. The compound [Ti(,5 -C5H5){1,2-C6H4(NnPr)2}Cl] (3) was obtained by treatment of [Ti(,5 -C5H5)Cl3] with 1,2-C6H4(NHnPr)2 in the presence of NEt3 in toluene. All the reported compounds were characterized by the usual analytical and NMR spectroscopic methods. The molecular structures of 3 and 7 were determined by single-crystal X-ray crystallography. The compounds described here were further investigated as potential olefin polymerization catalysts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] New Pentadentate Carboxylate-Derivatized Sulfur Ligands Affording Water Soluble Iron Complexes with [Fe(NS4)] Cores that Bind Small Molecules (CO, NO, PMe3) as Co-LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2004Dieter Sellmann Abstract In the search for polydentate sulfur ligands that are able to form water-soluble iron complexes which can bind nitrogenase relevant molecules, the new pentadentate ligands pyCO2MeS4,H2 [2,6-bis[2-mercapto-3-(methoxycarbonyl)phenylthio]dimethylpyridine] (1) and pyCO2HS4,H2 [2,6-bis(2-mercapto-3-carboxyphenylthio)dimethylpyridine] (2) having NS4 donor atom sets and terminal thiolate donors have been synthesized. The starting material was CO2MeS2,H2 (2,3-dimercapto benzoic acid methyl ester) which was alkylated with 2,6-bis[(tosyloxy)methyl]pyridine. The problem of specifically achieving regioselective mono-alkylation of this 1,2-benzene-dithiol derivative was solved by carrying out the alkylation of CO2MeS2,H2 at ,78 °C in the presence of stoichiometric amounts of a base. Saponification of 1 afforded the carboxylic acid derivative. Coordination of pyCO2MeS42, to FeII in the presence of co-ligands (L = CO, PMe3) yielded the complexes [Fe(L)(pyCO2MeS4)] where L = CO (5) or PMe3 (4). Upon treatment with NOBF4, complex 5 afforded [Fe(NO)(pyCO2MeS4)]BF4 (7) which could be subsequently converted to the isolable 19 valence electron species [Fe(NO)(pyCO2MeS4)] (8) upon reduction with N2H4. In the absence of potential co-ligands, coordination of pyCO2MeS42, to FeII afforded the dinuclear complex [Fe(pyCO2MeS4)]2 (6) whilst coordination to NiII gave [Ni(pyCO2MeS4)]x (3). Solubility of these complexes in water could be achieved by replacing the CO2Me groups with CO2H substituents. The ligand pyCO2HS42, afforded the iron complexes [Fe(L)(pyCO2HS4)] [L = CO (10) and PMe3 (12)] and [Fe(NO)(pyCO2HS4)]BF4 (11). Both 10 and 12 could be reversibly deprotonated to give the corresponding water-soluble salts (NMe4)2[Fe(L)(pyCO2S4)] with L = CO {(NMe4)2 [9]} and PMe3 {(NMe4)2 [13]}. The complexes were characterized by elemental analysis, spectroscopic methods and X-ray structural determinations. The molecular structure of [Fe(PMe3)(pyCO2HS4)] (12) was found to exhibit inter- and intramolecular O,H···O and O,H···S hydrogen bonds which serve as models for proton transfer steps from external sources to the active sites of metal sulfur enzymes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] (4-Acyl-5-pyrazolonato)titanium Derivatives: Oligomerization, Hydrolysis, Voltammetry, and DFT StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2003Francesco Caruso Abstract Twenty 4-acyl-5-pyrazolonato (Q) titanium derivatives of varied nuclearity have been synthesized from Ti(OR)4 or TiCl4 and characterized with spectroscopic methods (IR, NMR, ESI-MS). While Ti,(,-diketonato) cleavage is not seen in isolated solids, Ti,O(alkoxy) (or Ti,Cl) bonds cleave upon hydrolysis, leading to several structural forms, including oligomers. Ionic Q species with no Ti, i.e., obtained after Ti,Q cleavage, are seen for some Ti,Q derivatives by ESI-MS, which also indicates a varied nuclearity for a given species, e.g., the isolated polynuclear [Q2Ti-,-O]n has several "n" values. Mononuclear Ti complexes are obtained under rigorous anhydrous conditions. The cis structures of the mononuclear species (QT)2Ti(OCH3)2, QT = 3-methyl-4-(neopentylcarbonyl)-1-phenylpyrazol-5-onato have been analyzed with DFT methods. A trans influence is a major driving force that accounts for several sets of Ti,O bonds. One of the cis stereoisomers is 56 kcal/mol higher in energy than the other two. In contrast, all (QT)2TiCl2cis isomers show similar energies. Voltammetry of the mononuclear species (QT)2Ti(OnPr)2 and the antitumor tetranuclear compound [(QB)2Ti-,-O]4, (QB = 4-benzoyl-3-methyl-1-phenylpyrazol-5-onato) indicate that the TiIV is less prone to reduction to TiIII in the latter (Epc for the TiIV/TiIII couple is ,1.71 V and ,1.46 V versus Fc+/Fc, respectively). Potential antitumor compounds having a Ti/Q ratio of 1:1 do not disproportionate, unlike the equivalent acetylacetonato derivatives, and are water-soluble. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] A Rigid Molecular Scaffold Affixing a (Polypyridine)ruthenium(II)- and a Nickel(II)-Containing Complex: Spectroscopic Evidence for a Weakly Coupled Bichromophoric SystemEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2003Yann Pellegrin Abstract The synthesis of DppztBuSalH2 (7), a rigid conjugated ditopic ligand containing a Dppz (dipyrido[3,2- a:2,,3,- c]phenazine) skeleton and a salophen-type chelate, is reported. The complexes DppztBuSalNi (10), [Ru(bpy)2(DppztBuSalH2)]2+ (11), and [Ru(bpy)2(DppztBuSalNi)]2+ (12) have been prepared and characterised using common spectroscopic methods. Electrochemical, UV/Vis spectroelectrochemical and EPR studies were conducted on compounds 7, 10, 11, and 12. The singly reduced radical forms of 7 and 10 can be generated electrochemically, with the lone electron located on the low-lying phenazine ,*-molecular orbital. Complexes 11 and 12 show several reduction waves and electronic and EPR data obtained for the electrogenerated singly reduced species show them to be closely related to the radical species 7·, and 10·,, respectively. The presence of nickel(II) in compound 12 renders the addition of the second electron on the phenazine group reversible. Both 11 and 12 show common features on the cathodic side of their cyclic voltammograms, with reversible one-electron ruthenium-centred oxidation. An additional low-potential reversible-oxidation wave is observed for 12, and this is ascribed to oxidation of the nickel(II) ion. The combined spectroscopic data best describe the ruthenium-containing complexes as weakly coupled bichromophoric systems. Photophysical studies attest to the formation of a charge-separated state for 11, whereas a strong quenching is detected for 12. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Oreacerebrosides: Bioactive Cerebrosides with a Triunsaturated Sphingoid Base from the Sea Star Oreaster reticulatusEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2007Valeria Costantino Abstract The sea star Oreaster reticulatus contains, along with the known ophidiacerebrosides C,E, nine new glycosphingolipids named oreacerebrosides A,I. Their structures were elucidated by a combination of spectroscopic methods and chemical degradation. All compounds contain a 4,8,10-triunsaturated sphingoid base. Oreacerebrosides A,C have a ,-glucopyranoside as the sugar residue, as found in ophidiacerebrosides C,E and in all known compounds of this type; in contrast, oreacerebrosides D,I are the first examples of ,-galactosylceramides containing this unusual sphingoid base. Four representative glycosphingolipids were tested for cytotoxic activity on rat glioma C6 cells and were shown to be mildly cytotoxic; the glucosylceramides were more active than the galactosylceramides. In addition, oreacerebroside I, but not ophidiacerebroside E, was shown to exert proangiogenic activity and was able to increase VEGF-induced human endothelial cell proliferation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Meroterpenoid Pigments from Albatrellus flettii (Basidiomycetes),EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2007Barbara Koch Abstract The pigments responsible for the blue colour of the North American polypore Albatrellus flettii have been isolated and their structures elucidated by spectroscopic methods. Albatrellin, a dimeric meroterpenoid with a furylbenzoquinone chromophore, is accompanied by its 16-hydroxy and 16-oxo derivatives. The latter has recently been described as grifolone B from a Japanese collection of A. caeruleoporus. Based on the idea that albatrellin is formed in nature by oxidative coupling of a grifolinquinone with the furan derivative cristatin, the blue pigment was synthesized in vitro. The reaction could be applied to the synthesis of several analogues.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Iodinated Indole Alkaloids From Plakortis simplex , New Plakohypaphorines and an Evaluation of Their Antihistamine ActivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2004Francesca Borrelli Abstract Three new iodinated tryptophan derivatives, plakohypaphorines D,F (4,6), have been isolated from the Caribbean sponge Plakortis simplex. Their structures have been determined by applying spectroscopic methods and microwave-assisted selective dehalogenation. Compound 5 is the first naturally occurring triiodinated indole, while compound 6 is a unique metabolite because it possesses both chlorine and iodine atoms on the indole nucleus. We have evaluated the antihistamine activity of the whole series of plakohypaphorines A,F, but only the diiodinated analogues proved to be active: they display a specific antagonism of the noncompetitive type. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Full-length prion protein aggregates to amyloid fibrils and spherical particles by distinct pathwaysFEBS JOURNAL, Issue 9 2008Driss El Moustaine As limited structural information is available on prion protein (PrP) misfolding and aggregation, a causative link between the specific (supra)molecular structure of PrP and transmissible spongiform encephalopathies remains to be elucidated. In this study, high pressure was utilized, as an approach to perturb protein structure, to characterize different morphological and structural PrP aggregates. It was shown that full-length recombinant PrP undergoes ,-sheet aggregation on high-pressure-induced destabilization. By tuning the physicochemical conditions, the assembly process evolves through two distinct pathways leading to the irreversible formation of spherical particles or amyloid fibrils, respectively. When the PrP aggregation propensity is enhanced, high pressure induces the formation of a partially unfolded aggregated protein, AggHP, which relaxes at ambient pressure to form amorphous aggregates. The latter largely retain the native secondary structure. On prolonged incubation at high pressure, followed by depressurization, AggHP transforms to a monodisperse population of spherical particles of about 20 nm in diameter, characterized by an essentially ,-sheet secondary structure. When the PrP aggregation propensity is decreased, an oligomeric reaction intermediate, IHP, is formed under high pressure. After pressure release, IHP relaxes to the original native structure. However, on prolonged incubation at high pressure and subsequent depressurization, it transforms to amyloid fibrils. Structural evaluation, using optical spectroscopic methods, demonstrates that the conformation adopted by the subfibrillar oligomeric intermediate, IHP, constitutes a necessary prerequisite for the formation of amyloids. The use of high-pressure perturbation thus provides an insight into the molecular mechanism of the first stages of PrP misfolding into amyloids. [source] Escherichia coli thioredoxin inhibition by cadmiumFEBS JOURNAL, Issue 7 2004Asp2, Two mutually exclusive binding sites involving Cys3 Observations of thioredoxin inhibition by cadmium and of a positive role for thioredoxin in protection from Cd2+ led us to investigate the thioredoxin,cadmium interaction properties. We used calorimetric and spectroscopic methods at different pH values to explore the relative contribution of putative binding residues (Cys32, Cys35, Trp28, Trp31 and Asp26) within or near the active site. At pH 8 or 7.5 two binding sites were identified by isothermal titration calorimetry with affinity constants of 10 × 106 m,1 and 1 × 106 m,1. For both sites, a proton was released upon Cd2+ binding. One mole of Cd2+ per mole of reduced thioredoxin was measured by mass spectrometry at these pH values, demonstrating that the two binding sites were partially occupied and mutually exclusive. Cd2+ binding at either site totally inhibited the thiol,disulfide transferase activity of Trx. The absence of Cd2+ interaction detected for oxidized or alkylated Trx and the inhibition of the enzymatic activity of thioredoxin by Cd2+ supported the role of Cys32 at the first site. The fluorescence profile of Cd2+ -bound thioredoxin differed, however, from that of oxidized thioredoxin, indicating that Cd2+ was not coordinated with Cys32 and Cys35. From FTIR spectroscopy, we inferred that the second site might involve Asp26, a buried residue that deprotonates at a rather high and unusual pKa for a carboxylate (7.5/9.2). The pKa of the two residues Cys32 and Asp26 have been shown to be interdependent [Chivers, T. P. (1997) Biochemistry36, 14985,14991]. A mechanism is proposed in which Cd2+ binding at the solvent-accessible thiolate group of Cys32 induces a decrease of the pKa of Asp26 and its deprotonation. Conversely, interaction between the carboxylate group of Asp26 and Cd2+ at a second binding site induces Cys32 deprotonation and thioredoxin inhibition, so that Cd2+ inhibits thioredoxin activity not only by binding at the Cys32 but also by interacting with Asp26. [source] The relationship between thermal stability and pH optimum studied with wild-type and mutant Trichoderma reesei cellobiohydrolase Cel7AFEBS JOURNAL, Issue 5 2003Harry Boer The major cellulase secreted by the filamentous fungus Trichoderma reesei is cellobiohydrolase Cel7A. Its three-dimensional structure has been solved and various mutant enzymes produced. In order to study the potential use of T. reesei Cel7A in the alkaline pH range, the thermal stability of Cel7A was studied as a function of pH with the wild-type and two mutant enzymes using different spectroscopic methods. Tryptophan fluorescence and CD measurements of the wild-type enzyme show an optimal thermostability between pH 3.5,5.6 (Tm, 62 ± 2 °C), at which the highest enzymatic activity is also observed, and a gradual decrease in the stability at more alkaline pH values. A soluble substrate, cellotetraose, was shown to stabilize the protein fold both at optimal and alkaline pH. In addition, unfolding of the Cel7A enzyme and the release of the substrate seem to coincide at both acidic and alkaline pH, demonstrated by a change in the fluorescence emission maximum. CD measurements were used to show that the five point mutations (E223S/A224H/L225V/T226A/D262G) that together result in a more alkaline pH optimum [Becker, D., Braet, C., Brumer, H., III, Claeyssens, M., Divne, C., Fagerström, R.B., Harris, M., Jones, T.A., Kleywegt, G.J., Koivula, A., et al. (2001) Biochem. J.356, 19,30], destabilize the protein fold both at acidic and alkaline pH when compared with the wild-type enzyme. In addition, an interesting time-dependent fluorescence change, which was not observed by CD, was detected for the pH mutant. Our data show that in order to engineer more alkaline pH cellulases, a combination of mutations should be found, which both shift the pH optimum and at the same time improve the thermal stability at alkaline pH range. [source] Multifunctional Mesoporous Silica Material Used for Detection and Adsorption of Cu2+ in Aqueous Solution and Biological Applications in vitro and in vivoADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Qingtao Meng Abstract An inorganic,organic silica material (SBA,P2), prepared by immobilization of the 1,8-naphthalimide-based receptor P2 within the channels of the mesoporous silica material SBA-15, is characterized by transmission electron microscopy and several spectroscopic methods. SBA,P2 features a high affinity Cu2+ -specific fluorescence response in aqueous solution with a detection limit for Cu2+ of ca. 0.65,ppb (10,×,10,9,M) under optimized conditions. It can extract Cu2+ from the solution with only trace amounts remaining. Through isolating of the toxic ions within the mesopores of the silica, SBA,P2 has the potential to work as a toxicide for Cu2+ in living systems. The fluorogenical responses are reversible and do not vary over a broad (4.0 to 9.0) pH range suitable for application under physiological conditions. The fluorescence responses of Cu2+ in vitro (human breast cancer cells) and in vivo (five-day-old zebrafish) demonstrate the possibility of further application in biology. [source] Facile Controlled Synthesis and Spectroscopy of CdS1,xSex Alloy and (CdS)1,x@(CdSe)x Core,Shell NanotetrapodsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Mee Rahn Kim Abstract Nanotetrapods of alloy CdS1,xSex and core,shell (CdS)1,x@(CdSe)x are fabricated easily in water using ethylenediamine as a solvent-coordinating molecular template, and then their optical properties are investigated using diverse static and time-resolved spectroscopic methods. The arms of the alloy nanotetrapods have single-crystalline structures of CdS1,xSex without showing staking faults, while the arms of the core,shell nanotetrapods display polycrystalline shell structures of CdSe. The optical properties of CdS1,xSex, where Se atoms are isolated in the CdS lattice, are very different from those of (CdS)1,x@(CdSe)x, where banded CdSe passivates the CdS core. Compared with pure CdS nanotetrapods, the photoluminescence of CdS0.9Se0.1 shifts to the red by 40,nm, whereas that of (CdS)0.9@(CdSe)0.1 does so only by 5,nm. Although the mean luminescence lifetime of alloy CdS1,xSex is shorter than that of pure CdS, it is still much longer than that of core-shell (CdS)1,x@(CdSe)x. [source] New Diterpenoid Alkaloids from Aconitum liangshanicumHELVETICA CHIMICA ACTA, Issue 4 2010Zhong-Tang Zhang Abstract One new C19 -diterpenoid alkaloid, named liangshantine (1), and three new C20 -diterpenoid alkaloids, liangshansines A,C (2,4, resp.), as well as eight known compounds, were isolated from the roots of Aconitum liangshanicum. The structures of these new alkaloids were elucidated by spectroscopic methods. [source] Four New 1,4-Benzoquinone Derivatives and One New Coumarin Isolated from Ardisia gigantifoliaHELVETICA CHIMICA ACTA, Issue 2 2010Hongwei Liu Abstract Four new 1,4-benzoquinone derivatives, belamcandaquinones J (1), K (2), L (3), and M (4), and one new coumarin, 5, were isolated from the rhizome of Ardisia gigantifolia. Their structures were established by means of spectroscopic methods, and their cytotoxicity was tested in vitro against the cell lines PC-3, EMT6, A549, Hela, RM-1, and SGC7901. In comparison with cisplatin, compound 5 showed strong cytotoxicity with an IC50 value of <30,,M against the cell lines PC-3 and A549. Compounds 1,4 showed no cytotoxicity against all cell lines. [source] Four New Lignans with a Bicyclo[3.3.1]nonadienemethanol Skeleton from Cunninghamia lanceolataHELVETICA CHIMICA ACTA, Issue 10 2009Ching-Kuo Lee Abstract Four unique bicyclo[3.3.1]nonadienemethanol lignans, designated lanceolatanins A (1), B (2), C (3), and D (4), along with one previously known compound, isolariciresinol (5), were isolated from the MeOH extracts of the heartwood of Cunninghamia lanceolata. Their structures were elucidated by application of various spectroscopic methods, including 1D- and 2D-NMR techniques, to their acetylated derivatives 1a, 2a, 3a, and 4a. Their possible biosynthetic formations are also discussed. [source] Three New Diarylheptanoids from Myrica nanaHELVETICA CHIMICA ACTA, Issue 8 2009Jun-Feng Wang Abstract Three new cyclic diarylheptanoids myricananins F,H (1,3, resp.), along with five known ones, 4,8, were isolated from the roots of Myrica nana. Compound 3 has been obtained by Nagai et,al. by reduction of porson with NaBH4. In this work, compound 3 was isolated from natural origin for the first time. The structures of 1,8 were elucidated using spectroscopic methods. [source] | ||||||||||||||||||||||||||||||||||||||||||||||