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Spectroscopic Data (spectroscopic + data)
Kinds of Spectroscopic Data Selected AbstractsARCHAEOMETRICAL INVESTIGATION OF SICILIAN EARLY BYZANTINE GLASS: CHEMICAL AND SPECTROSCOPIC DATA*ARCHAEOMETRY, Issue 1 2010R. ARLETTI A series of early Byzantine glasses, recovered in Ganzirri (Sicily, Italy), was analysed for major, minor and trace elements. All the analysed fragments were found to be natron-based silica,lime glass. Concerning minor and trace elements, the samples can be divided into two groups: glass with high Fe, Ti and Mn contents (HIMT glass) and glass with low levels of Fe, Ti and Mn. These results, strictly in agreement with literature data for glass of the Mediterranean region, can be interpreted as a consequence of the wide trade network established in this region and of the intense circulation of raw glass and artefacts from different Mediterranean areas. X-ray absorption spectroscopy studies at Fe and Mn K-edges, performed on HIMT glass, indicate that Fe is in the oxidized form while Mn is in the reduced form. [source] The Conformation of Alkyl Benzyl Alcohols Studied by ab initio MO Calculations , A Comparison with IR and NMR Spectroscopic DataEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2004Osamu Takahashi Abstract Ab initio MO calculations were carried out for the conformations of a series of alkyl-substituted benzyl alcohols C6H5CH2CHOH,R (R = CH3, C2H5, iPr, tBu) at the MP2/6-311G(d,p)//MP2/6-31G(d) level. It was found that the conformation where the OH group is gauche to the phenyl group is the most stable. The geometry where both the OH and R groups are close to phenyl is the second most stable. This finding has been interpreted on the grounds of the attractive OH/, and CH/, hydrogen bonds and a repulsive van der Waals interaction between vicinal CH groups. NMR nuclear Overhauser effects, spin-coupling data, and IR spectroscopic data are consistent with the conclusion given by the MO calculations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Characterization of Copper Complexes Containing the Tripodal N7 Ligand Tris{2-[(pyridin-2-ylmethyl)amino]ethyl}amine (=N,-(Pyridin-2-ylmethyl)- N,N -bis{2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine): Equilibrium, Spectroscopic Data, and Crystal Structures of Mono- and Trinuclear Copper(II) ComplexesHELVETICA CHIMICA ACTA, Issue 9 2005Christian Gérard The stability constants of the CuII chelates with the tripodal heptadentate ligand tris{2-[(2-pyridylmethyl)amino]ethyl}amine (=N,-(pyridin-2-ylmethyl)- N,N -bis{2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine; tpaa), determined by potentiometry and UV spectrometry, show the formation of [Cu(tpaaH)]3+ and [Cu(tpaa)]2+ species. In the solid state, two mononuclear CuII compounds, [Cu(tpaa)](PF6)2 (1) and [Cu(tpaaH)](ClO4)3,H2O (2), and one trinuclear [Cu3(tpaa)2(ClO4)2](ClO4)4,2,H2O (3) complex were isolated and characterized by IR, UV/VIS, and EPR spectroscopy. An X-ray structure of the mononuclear protonated complex 2 shows that the Cu2+ ion has a distorted square-pyramidal geometry (,=0.21). and the proton is bound to the secondary-amine function of one uncoordinated arm of the tripod ligand (Fig.,4). The crystal lattice for 2 is stabilized by the H-bonds between the N-atom of the free pyridinyl group with the proton of the free secondary-amine function of the neighboring molecule. The linear trinuclear complex 3 consists of two entities of the pyramidal mononuclear complex 1 bound to the third central Cu2+ ion by the free unprotonated arms of the ligands in equatorial position (Fig.,5). The octahedral geometry of the third CuII atom is achieved by two perchlorate anions in the axial positions. The redox properties of 1,3 compounds was examined by cyclic voltammetry. [source] Analysis of Single-Molecule Fluorescence Spectroscopic Data with a Markov-Modulated Poisson ProcessCHEMPHYSCHEM, Issue 14 2009Mark Jäger Dr. Abstract We present a photon-by-photon analysis framework for the evaluation of data from single-molecule fluorescence spectroscopy (SMFS) experiments using a Markov-modulated Poisson process (MMPP). A MMPP combines a discrete (and hidden) Markov process with an additional Poisson process reflecting the observation of individual photons. The algorithmic framework is used to automatically analyze the dynamics of the complex formation and dissociation of Cu2+ ions with the bidentate ligand 2,2,-bipyridine-4,4,dicarboxylic acid in aqueous media. The process of association and dissociation of Cu2+ ions is monitored with SMFS. The dcbpy-DNA conjugate can exist in two or more distinct states which influence the photon emission rates. The advantage of a photon-by-photon analysis is that no information is lost in preprocessing steps. Different model complexities are investigated in order to best describe the recorded data and to determine transition rates on a photon-by-photon basis. The main strength of the method is that it allows to detect intermittent phenomena which are masked by binning and that are difficult to find using correlation techniques when they are short-lived. [source] Layered [BaM(C3H2O4)2(H2O)4] (M = Fe or Co) Complexes , Spectroscopic, Magnetic and Thermal StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2003Izaskun Gil de Muro Abstract Complexes with formula [BaM(C3H2O4)2(H2O)4], where M = Fe or Co, were synthesised and characterised. These two types of complexes are isostructural and crystallise in the Pccn space group. Their structure consists of two-dimensional networks of octahedral MO6 polyhedra in which the transition metal ions are coordinated by bridging malonate ligands, through the O-C-O atoms. These M-malonate units are extended along the crystallographic [101] plane. Spectroscopic data are consistent with the cations being in a high-spin octahedral symmetry. The two types of compounds exhibit 2D antiferromagnetic interactions as well as weak ferromagnetism below the Néel temperature, as a result of an intralayer misalignment of the spins. Thermal treatment of the metallo-organic precursors gave rise to BaMO3,y oxides at lower temperatures and reaction times than those found in the literature using the ceramic method. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003). [source] Diastereoselective synthesis of chloro- and fluoro-aniline containing phosphonate esters in a three-component condensationHETEROATOM CHEMISTRY, Issue 4 2010Malek Taher Maghsoodlou New phosphonate ester derivatives were obtained by in situ stereo-specific reaction between triphenyl phosphite and dialkyl acetylenedicarboxylates in the presence of a series of halogenated anilines. Spectroscopic data and X-ray crystallography analysis are in agreement with the gauche arrangement for the two vicinal protons in the structures. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:222,227, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20600 [source] Structures and properties of two diastereomeric cyclic sulfites derived from cis -3,4-di- tert -butylthiolane-3,4-diol and thionyl chlorideHETEROATOM CHEMISTRY, Issue 7 2003Sanae Tanaka cis-3,4-Di-tert-butylthiolane-3,4-diol (1) was treated with an equimolar amount of thionyl chloride in the presence of triethylamine or pyridine in several solvents of different polarity to furnish two diastereomeric sulfites 2a and 2b generally in excellent combined yields. Although 2a was consistently formed as the major diastereomer when pyridine was used as the base, 2a and 2b were formed in approximately equal amounts when triethylamine was used as the base in polar solvents. X-ray crystallographic analyses revealed that the SO group of 2a is anti to the thiolane ring and that of 2b syn to the thiolane ring. Density functional theory calculations (B3LYP/6-31G* level) revealed that 2a is less stable than 2b by 1.28 kcal mol,1, although 2a was formed generally as the predominant diastereomer. Spectroscopic data of 2a and 2b are discussed with emphasis on comparison with those obtained by calculations. Treatment of 2a and 2b with m-chloroperbenzoic acid resulted in the oxidation of the divalent sulfur atom of the thiolane ring and not the sulfite sulfur atom. The above oxidations took place exclusively at the syn-side with respect to the tert-butyl groups.© 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:587,595, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10192 [source] Supercapacitor studies of electrochemically deposited PEDOT on stainless steel substrateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007S. Patra Abstract There has been increasing interest on various properties and applications of electronically conducting polymers. Polyethylenedioxythiophene (PEDOT) is an interesting polymer of this type as it exhibits very high ionic conductivity. In the present study, PEDOT has been electrochemically deposited on stainless steel (SS) substrate for supercapacitor studies. PEDOT/SS electrodes prepared in 0.1M H2SO4 in presence of a surfactant, sodium dodecylsulphate (SDS), have been found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H2SO4, concentration of SDS, potential of deposition, and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes have been studied. SC values as high as 250 F/g in 1M oxalic acid have been obtained during the initial stages of cycling. However, there is a rapid decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Hierarchical principal component analysis (PCA) and projection to latent structure (PLS) technique on spectroscopic data as a data pretreatment for calibrationJOURNAL OF CHEMOMETRICS, Issue 4 2001K. Janné Abstract Spectroscopic data consists of several hundred to some thousand variables, wherein most of the variables are autocorrelated. When PCA and PLS techniques are used for the interpretation of these kinds of data, the loading plots are usually complex due to the covariation in the spectrum, and therefore difficult to correlate to the corresponding score plot. One of the standard methods used to decrease the influence of light scatter or shifts of the spectra is the multiplicative scatter correction technique. Another technique is the hierarchical multiblock segmentation technique, where new variables are created from the original data by blocking the spectra into sub spectra, and then projecting the sub spectra by PCA. These new variables are then used in the coming PCA or PLS calculations. These techniques reduce the random and non-wanted signals from e.g. light scatter, but still conserve all systematic information in the signals, but the greatest advantage is that the technique gives an easier interpretation of the correlation between scores and the loadings. Two examples are presented; the attenuated total reflection (ATR) and NIR, which show the advantages as well as the implementation of the method. Copyright © 2001 John Wiley & Sons, Ltd. [source] Ring transformations of heterocyclic compounds.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 20022,4,6-Triarylpyrylium perchlorates 1 react with methyleneindolines 3in situ generated from the corresponding methylindolium salts 2, which are spiro-fused with a cycloalkane, benzanellated cycloalkene or a heterocyclic system. These diastereoselective 2,5-[C4+C2] pyrylium ring transformations are carried out in the presence of triethylamine/acetic acid in boiling ethanol to give the dispiroindolines 4 with a trans configuration of the more bulky substituents at the cyclohexadiene ring. By the same type of transformation the dispiro compounds 7/10 with an additional fused benzene ring are obtained from the pyrylium salt 1a and 6/9, the benzo-fused analogues of 3. Spectroscopic data of the transformation products as well as their mode of formation are discussed. [source] Ring transformations of heterocyclic compounds.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2002The synthesis of pyrido[1,2- a]indolium perchlorates 8,11 from 2,4,6-triarylpyrylium perchlorates 1 and 2-methyl-3H -indoles 6,9 in the presence of a basic condensing agent (anhydrous sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) in ethanol by a 2,4-[C3+C2N] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed. [source] Improved physical stability of amorphous state through acid base interactionsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009Chitra Telang Abstract To investigate role of specific interactions in aiding formation and stabilization of amorphous state in ternary and binary dispersions of a weakly acidic drug. Indomethacin (IMC), meglumine (MU), and polyvinyl pyrollidone (PVP) were the model drug, base, and polymer, respectively. Dispersions were prepared using solvent evaporation. Physical mixtures were cryogenically coground. XRPD, PLM, DSC, TGA, and FTIR were used for characterization. MU has a high crystallization tendency and is characterized by a low Tg (17°C). IMC crystallization was inhibited in ternary dispersion with MU compared to IMC/PVP alone. An amorphous state formed readily even in coground mixtures. Spectroscopic data are indicative of an IMC,MU amorphous salt and supports solid-state proton transfer. IMC,MU salt displays a low Tg,,,50°C, but is more physically stable than IMC, which in molecular mixtures with MU, resisted crystallization even when present in stoichiometric excess of base. This is likely due to a disrupted local structure of amorphous IMC due to specific interactions. IMC showed improved physical stability on incorporating MU in polymer, in spite of low Tg of the base indicating that chemical interactions play a dominant role in physical stabilization. Salt formation could be induced thermally and mechanically. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2149,2159, 2009 [source] Phase-rotation in in-vivo localized spectroscopyCONCEPTS IN MAGNETIC RESONANCE, Issue 3 2007Saadallah Ramadan Abstract Phase-rotation is an alternative method to phase-cycling in acquisition of magnetic resonance spectroscopic data. However, there has only been two papers describing its implementation in point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) to date. This article aims to introduce and explain the principles of phase-rotation, describe the implementations that were carried out so far in the current literature, compare phase-rotation and phase-cycling experimentally, and introduce the application of phase-rotation in double-quantum filtered (DQF) spectroscopy. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 147,153, 2007 [source] Optical studies on ZnO films prepared by sol-gel methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2009T. Ghosh Abstract A standard sol-gel method was used to deposit ZnO thin films of suitable thickness on glass substrate. The optical characteristics of the visible to infrared range on thermal stress were critically observed. Morphological signature of the films was detected by X-ray diffraction (XRD) and the crystallite size determined by Scherrer method from XRD data were consistent with grain size estimated from spectroscopic data through Meulenkamp equation. The optical band gap value from the transmission spectrum was found to corroborate with the existing works. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and Structure Determination of Selenium(IV) CyanidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 30 2008Stefanie Fritz Abstract The reaction of SeF4 with Me3SiCN did not result in thepreparation of the designated Se(CN)4 but Se(CN)F3 and Se(CN)2F2 were obtained as first known selenium(IV)cyanide compounds and characterized by their NMR spectra. Se(CN)2F2 was crystallized as 1,2-dimethoxyethane solvate as well as the corresponding tellurium compound Te(CN)2F2 with very similar structures. NMR spectroscopic data of some more miscellaneous tellurium cyanides and the crystal structures of solvates of Se(CN)2 and oxygen-bridged TeO(CN)2 are presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Mechanism-Based Inactivation of Coenzyme B12 -Dependent 2-Methyleneglutarate Mutase by (Z)-Glutaconate and Buta-1,3-diene-2,3-dicarboxylateEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006Wolfgang Buckel Abstract In the presence of holo 2-methyleneglutarate mutase, buta-1,3-diene-2,3-dicarboxylate and (Z)-glutaconate [(Z)-pent-2-ene-1,5-dicarboxylate], but not (E)-glutaconate, each induced homolysis of the Co,C bond of coenzyme B12 to afford cob(II)alamin and the 5,-deoxyadenosyl radical. The latter probably added to the double bond in (Z)-glutaconate and one of the double bonds in buta-1,3-diene-2,3-dicarboxylate to afford a corresponding "radical adduct". The formation of new radicals and cob(II)alamin was diagnosed by UV/Visible and EPR spectroscopy. (Z)-Glutaconate rapidly inactivated the mutase with formation of aquocobalamin, which was possibly derived by electron transfer from cob(II)alamin to the radical adduct. In contrast, buta-1,3-diene-2,3-dicarboxylate was a much slower inactivator. In this case, the spectroscopic data revealed a relatively stable complex of the radical adduct with cob(II)alamin in the active site of the enzyme. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Solvent-Mediated Redox Transformations of Ytterbium Bis(indenyl)diazabutadiene ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2005Alexander A. Trifonov Abstract The reactions of diamagnetic [(C9H7)2Yb(THF)2] (2) and [rac -(CH2 -1-C9H6)2Yb(THF)2] (3) with tBuN=CH,CH=NtBu (DAD) in toluene result in the formation of the paramagnetic complexes [(C9H7)2Yb(DAD)] (4) and [rac- (CH2 -1-C9H6)2Yb(DAD)] (5), respectively. The IR, UV/Vis, and 1H NMR spectroscopic data, the magnetic properties, and the single-crystal X-ray diffraction studies of 4 and 5 indicate that in the solid state and in noncoordinating media both complexes are ytterbium(III) derivatives containing the DAD radical-anion, whereas the 1H NMR and UV/Vis spectra of solutions of 4 and 5 in the coordinating solvent THF give evidence for divalent ytterbium. Recrystallization of 4 and 5 from THF/hexane results in the recovery of the starting ytterbium complexes 2 and 3 due to an unusual redox substitution of the radical anion of diazabutadiene by THF in the coordination sphere of ytterbium. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Characterization by NMR Spectroscopy, X-ray Analysis and Cytotoxic Activity of the Ruthenium(II) Compounds [RuL3](PF6)2(L = 2-Phenylazopyridine or o -Tolylazopyridine) and [RuL'2L"](PF6)2(L', L" = 2-Phenylazopyridine, 2,2'-Bipyridine)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2005Anna C. G. Hotze Abstract Tris(ligand) complexes [RuL3](PF6)2 (L = 2-phenylazopyridine or o -tolylazopyridine) and mixed ligand [RuL'2L"](PF6)2 (L' and L" are 2-phenylazopyridine or 2,2'-bipyridine) have been synthesized, structurally characterized and investigated for cytotoxic activity. These complexes are important to study the hypothesis that the compound ,-[Ru(azpy)2Cl2] (azpy = 2-phenylazopyridine) exhibits a high cytotoxicity due to its two cis chloride ligands, which might be exchanged for biological targets as DNA. Molecular structures of mer -[Ru(azpy)3](PF6)2 (1) and mer -[Ru(tazpy)3](PF6)2 (5) (tazpy = o -tolylazopyridine) have been determined by X-ray diffraction. Series of complexes [RuL3](PF6)2 and [RuL'2L"](PF6)2 show interesting NMR spectroscopic data; e.g. the spectrum of mer -[Ru(azpy)3](PF6)2 (1) shows extremely broadened resonances at room temp. but sharpened resonances at low temperature. In the 1H NMR spectra of compounds [Ru(azpy)2(bpy)]2+ and [Ru(bpy)2(azpy)]2+ (bpy = 2,2-bipyridine), respectively, less broadened (room temp.) or completely sharp resonances (room temp.) occur in comparison to 1 (under same conditions). By selecting the right temperature and/or concentration, NMR spectra of these series of compounds have been resolved using 2D COSY and NOESY NMR spectroscopy. Remarkably, the cytotoxicity data against a series of human tumor cell lines (A498, EVSA-T, H226, IGROV, M19, MCF-7 and WIDR) show a moderate cytotoxicity for these series of tris(ligand) complexes. So, even though no chloride ligands are present in these tris(ligand) complexes, a considerable cytotoxic activity is observed. This would imply that the 2-phenylazopyridine ruthenium(II) complexes act by a completely different mechanism than the well-known cisplatin. This finding is important, because an anticancer compound acting via a different mechanism is a prerequisite in designing new anticancer drugs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Template Synthesis, Crystal Structure and Luminescent Properties of Neutral N4O3 Tripodal LnIIIL Complexes (LnIII = La3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+ or Lu3+; H3L = Tris{[3,-(2,,-pyridyl)-5,- tert -butyl-2,-hydroxybenzylidene-2-imino]ethyl}amine)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2004Wai-Kwok Wong Abstract In the presence of Ln3+ (Ln = La, Eu, Gd, Tb, Dy, Ho, Er, Tm or Lu), tris(2-aminoethyl)amine condensed with three equivalents of 3-(2,-pyridyl)-5- tert -butyl-2-hydroxybenzaldehyde in methanol to give the neutral Schiff-base complex LnIIIL (Ln = La 1, Eu 2, Gd 3, Tb 4, Dy 5, Ho 6, Er 7, Tm 8 and Lu 9; H3L = tris{[3,-(2,,-pyridyl)-5,- tert -butyl-2,-hydroxybenzylidene-2-imino]ethyl}amine). The structures of compounds 4,7 were determined by X-ray crystallography. The crystal structure analyses revealed that the Schiff base behaves as a tri-deprotonated heptadentate ligand encapsulating the lanthanide metal ion within the N4O3 cavity, with all the pyridyl groups being pendant. Solution spectroscopic data suggest that the LnIIIL complexes remain intact in methanol and exist as nine-coordinate non-electrolytes with the lanthanide metal ions coordinated to the N4O3 cavity of the tripodal Schiff base and two solvent molecules. The solution photoluminescent properties of these lanthanide Schiff-base complexes were also examined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Structural Studies of Lithium Telluro- and Seleno-Phosphorus CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2003Robert P. Davies Abstract Lithium tellurophosphinite [Ph2PTe][Li(TMEDA)1.33(THF)1.33] (4), ditellurophosphinate, [Ph2PTe2][Li(THF)3.5(TMEDA)0.25] (5), and selenotellurophosphinate [Ph2P(Se)Te][Li(THF)2(TMEDA)] (6) complexes have been prepared from the insertion/oxidation reactions of lithiated secondary phosphanes with elemental chalcogens and characterised by X-ray crystallography. Compounds 4,6 contain no tellurium,lithium bonding interactions in the solid state, instead existing as ion-separated species with THF/TMEDA-solvated lithium cations. Reaction of dilithiated primary phosphanes with more than three equivalents of elemental selenium gives [{(c -C6H11)P(Se)(SeLi)}2·2TMEDA] (7) via a phosphorus-phosphorus coupling reaction. Solid state characterisation of 7 reveals the organo groups in the tetradentate tetraselenohypodisphosphinate ligand to be in an anti conformation to one another and each lithium atom to be coordinated by two selenium atoms, one from each of the diselenophosphinate groups. Multinuclear NMR spectroscopic data are consistent with retention of the solid-state structures of 4,7 in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Investigations on 1-MetallaindanesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2003Marcel Schreuder Goedheijt Abstract 1-Mercuraindane (6) was prepared in three steps from 1-bromo-2-(2-bromoethyl)benzene (3) and converted into 1-magnesaindane (1) by reaction with magnesium. In solution, 6 was observed to occur in a remarkable dimer/trimer equilibrium, whereas 1 forms a dimer. From 1 and dichlorozirconocene, the 1-zirconaindane 2 was obtained, which reacted with B(C6F5)3 to form the adduct 13. According to spectroscopic data, 13 is formed by attack of the ,-methylene carbon atom at the boron atom and has a zwitterionic structure with weak interactions between the zirconium ion and one of the ortho -fluorine atoms. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Enol Forms of 1,3-Indanedione, Their Stabilization by Strong Hydrogen Bonding, and Zwitterion-Assisted InterconversionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2010Mark Sigalov Abstract By analyzing NMR spectroscopic data, and supported by IR, UV/Vis, Raman, dielectrometry, and DFT techniques, a comprehensive study of the 1:2 adducts of picolinaldehyde and 1,3-indanediones is presented. The parent indanedione derivative 5 exists in an equilibrium between all-keto and enol forms, the latter being stabilized by an intramolecularO,H···N hydrogen bond. Only the all-keto form was observed in the 5,6-dimethoxy compound 6, whereas solely the enol tautomer was observed with its 5,6-dichloro analogue 7. Polar solvents and low temperatures shift the equilibrium towards the enol tautomer in 5. The structure of adduct 8, formed with isonicotinaldehyde, prevents the formation of intramolecular O,H···N hydrogen bonds and thus it exists in the all-keto form in low polar solvents. However, in DMSO solutions it adopts a zwitterionic form with a strong anionic O,···H···O hydrogen bond. Thus, the enol form in indanedione adducts was unequivocally characterized in solution and the factors that determine the keto,enol tautomerism, namely electronic effects, solvent, temperature, and intramolecular hydrogen bonds, have been methodically studied by spectroscopic and quantum mechanical methods. [source] Drastic Solid-State Fluorescence Enhancement Behaviour of Phenanthro[9,10- d]imidazole-Type Fluorescent Hosts upon Inclusion of Carboxylic AcidsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2009Yousuke Ooyama Abstract The crystals of phenanthro[9,10- d]imidazole-type fluorescent host 1 exhibit drastic fluorescence enhancement behaviour with a redshift in the emission maximum upon enclathration of various carboxylic acids such as formic acid, acetic acid and propionic acid. The optical changes are greatly dependent on the identity of the enclathrated carboxylic acids. The fluorescent clathrate compounds are formed not only by cocrystallization from carboxylic acid solutions but also by solid (fluorescent host),gas (carboxylic acid vapour) contact. Furthermore, when the acetic acid inclusion crystals are exposed to propionic acid vapour, acetic acid is gradually replaced by propionic acid. The guest exchange of the inclusion crystals was accompanied with colour and fluorescent intensity changes. The X-ray structural analyses of the guest-free and carboxylic acid inclusion compounds demonstrated that the destructions of the ,,, interactions, and the intermolecular hydrogen bonds binding fluorophores were induced by the enclathrated carboxylic acid molecules. Moreover, the imidazole ring of the host is protonated by the enclathrated carboxylic acid proton. On the basis of the spectroscopic data and the crystal structures, the effects of the enclathrated carboxylic acid on the solid-state photophysical properties of the clathrate compounds are discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Apralactone A and a New Stereochemical Class of Curvularins from the Marine Fungus Curvularia sp.EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 30 2008Hendrik Greve Abstract Chemical investigations of the cytotoxic extract of the marine fungus Curvularia sp. (strain no. 768), isolated from the red alga Acanthophora spicifera, yielded the novel macrolide apralactone A (1), as well as the antipodes of curvularin macrolides 2,7. Compound 8, a dimeric curvularin was recognised as an artefact. The structures of 1,8 were elucidated by interpretation of their spectroscopic data (1D and 2D NMR, CD, MS, UV and IR). Apralactone A (1) is a 14-membered phenyl acetic acid macrolactone, and the first such compound with a 4-chromanone substructure. Compounds 1, 2, 4, 5 and 6 were found to be cytotoxic towards human tumor cell lines with mean IC50 values in the range of 1.25 to 30.06 ,M. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] J -Based Analysis and DFT,NMR Assignments of Natural Complex Molecules: Application to 3,,7-Dihydroxy-5,6-epoxycholestanesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2008Jesús Javier Poza Abstract In order to reproduce the stereochemical dispositions of the epoxy and hydroxy functionalities, four 3,,7-hydroxy-5,6-epoxycholestanes were easily prepared from cholesterol, and their NMR spectroscopic data were experimentally obtained from 1D and 2D NMR experiments. An exhaustive QM- J -based analysis was then performed to replicate the experimental H,H and C,H coupling constants as well as the 13C NMR chemical shifts. The B3LYP GIAO methodology with the 6-311-G(d,p) basis set was chosen and showed that the data obtained from rings A and B were sufficient to calculate the correct stereochemistry of the 5,6-epoxy and 7-hydroxy groups. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Mannich and O -Alkylation Reactions of Tetraalkoxyresorcin[4]arenes , The Use of Some Products in Ligand-Assisted ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2006Benjamin R. Buckley Abstract The measurement of the pKa of racemic tetramethoxyresorcin[4]arenes explains the failure to obtain good yields in attempted Mannich reactions of these substrates under classical reaction conditions. The failure is related to the lack of adequate concentrations of the iminium ions that results from the reduced acid strength of tetraalkoxyresorcin[4]arenes compared with that of the parent octahydroxyresorcin[4]arenes. However, the preparation of a series of Mannich bases derived from racemic tetraalkoxyresorcin[4]arenes was accomplished under microwave-assisted aprotic reaction conditions and the use of preformed iminium ion intermediates. When the reactions were carried out with the use of chiral bis(aminol) ethers, mixtures of diastereomers were obtained that could be separated by flash chromatography. The absolute configurations of the enantiomerically pure tetrabenzoxazine derivatives were established in some cases by X-ray crystallographic analysis and by a comparison of the nuclear magnetic resonance spectroscopic data. The alkylation of racemic tetramethoxyresorcin[4]arenes was achieved with the use of an excess of 2-bromo- N -[(R)-(+)-(,-methylbenzyl)]acetamide in acetonitrile containing potassium carbonate. Enantioselective ligand-assisted reactions of aromatic aldehydes are also reported with the use of dialkylzinc reagents both in the absence and in the presence of terminal alkynes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis and Absolute Configuration of (+)-Pseudodeflectusin: Structural Revision of Aspergione BEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2006Fumiyo Saito Abstract We report herein the total synthesis and determination of the absolute configuration of (+)-pseudodeflectusin. The total synthesis of (+)-pseudodeflectusin starting from o -anisic aid was achieved in 11 total steps with an overall yield of 2.0,%. The 1H- and 13C NMR spectroscopic data of our synthetic pseudodeflectusin was identical to that of the natural compound. The absolute configuration of (+)-pseudodeflectusin was determined by chiral HPLC and X-ray crystallographic analyses. We also synthesized the proposed structure of aspergione B, whose 1H- and 13C NMR spectroscopic data is identical to that of pseudodeflectusin. The 1H- and 13C NMR spectra of our synthetic aspergione B were different from those of the natural compound reported by Proksch et al. Our results confirm that aspergione B and pseudodeflectusin are, in fact, the same compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis and Characterization of PY2- and TPA-Appended Diphenylglycoluril Receptors and Their Bis-CuI ComplexesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2006Vera S. I. Sprakel Abstract A number of metallohosts mimicking dinuclear copper oxygenases have been designed and synthesized. These metallohosts combine a substrate binding site, i.e. the diphenylglycoluril basket receptor, with two types of metal-binding ligands, viz. tri-coordinating bis(2-ethylpyridine)amine (PY2) and tetra-coordinating tris(2-methylpyridine)amine (TPA). The preparation of the bis-CuI complexes of the ligand-appended receptors and their characterization by NMR are reported. NMR spectroscopic data provide evidence for a dynamic inclusion behavior of some of the pyridine moieties in the receptor of both the metal-free ligands and the CuI complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Isolation and Structure Determination of Aplidinones A,C from the Mediterranean Ascidian Aplidium conicum: A Successful Regiochemistry Assignment by Quantum Mechanical 13C NMR Chemical Shift CalculationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2005Anna Aiello Abstract A chemical investigation of a Mediterranean ascidian, Aplidium conicum, has resulted in the isolation of the new metabolites aplidinone A (1), B (2), and C (3). The structures of aplidinones A,C were determined by interpretation of spectroscopic data, whereas the regiochemistry was determined by the comparison of experimental 13C NMR chemical shifts with those predicted by GIAO shielding calculations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Solid-State Structure and Tautomerism of 2-Aminotroponimines Studied by X-ray Crystallography and Multinuclear NMR SpectroscopyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2004Rosa M. Claramunt Abstract Structural studies in the solid state by X-ray crystallography and by 13C and 15N CPMAS NMR spectroscopy carried out on a series of 2-aminotroponimine derivatives 2,5 has allowed to establish the existence of hydrogen bonding and to determine the most stable tautomer. Almost all the structures reflect the classical double-well potential function for the N,H···N hydrogen bonds. Only in the case of the compound N -(pyrrol-1-yl)-2-(pyrrol-1-ylamino)troponimine (5) the crystal structure shows two independent molecules, one with a classical hydrogen bond and another with either a single-well or a low-barrier hydrogen bond. The structure of this compound is discussed with the use of the solid-state NMR spectroscopic data. 2-Aminotropones, as intermediates to the 2-aminotroponimines, show the oxo-tautomer as the stable form. B3LYP/6-31G* calculations are used to rationalise the experimental results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] | |||||||||||||||||||||||||||||||||||||