Search results for " Spectroscopy"
showing 10 items of 6851 documents
Iron (II) isothiocyanate complexes with substituted pyrazines: Experimental and theoretical views on their electronic structure
2015
Abstract Synthesis, structural, magnetic, Mossbauer and thermal studies of isothiocyanate iron (II) complexes with substituted pyrazines (iodo-, bromo- and amino-derivatives) are discussed here. Complexes with iodo- and bromo-derivatives were found to have the composition [Fe(Ipz)2(SCN)2(H2O)2]·2Ipz (1) and [Fe(Brpz)2(SCN)2(H2O)2]·2Brpz (2), whereas in the case of amino-functionalized pyrazine the formation of [Fe(NH2pz)4(SCN)2] (3) was observed. 3D organization of the molecular complexes is stabilized within different hydrogen, halogen and lone pair–π interactions. Spin state of iron (II) ions in 1–3 was determined as high spin by Mossbauer and magnetic measurements. DFT calculations for t…
Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications
2009
Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status of research in the development of CdTe and CdZnTe detectors by a comprehensive survey on the material properties, the device characteristics, the different techniques for improving the overall detector…
Solvated copper(I) hexafluorosilicate π-complexes based on [Cu2(amtd)2]2+ (amtd = 2-allylamino-5-methyl-1,3,4-thiadiazole) dimer
2016
[Cu2(amdt)2]SiF6·C6H6 and [Cu2(amdt)2(H2O)2]SiF6·CH3CN·2H2O (amdt = 2-allylamino-5- methyl-1,3,4-thiadiazole) were obtained by alternating-current electrochemical synthesis, starting from water–acetonitrile–benzene mixtures containing 2-allylamino-5-methyl-1,3,4- thiadiazole and CuSiF6·4H2O. The electrochemical reduction of the saturated copper hexafluorosilicate water solution beneath the neatly poured layer of acetonitrile-benzene amdt solution resulted in the formation of crystalline [Cu2(amdt)2]SiF6·C6H6. The initial stirring of the same mixture before subjecting it to the electrochemical reduction resulted in the formation of [Cu2(amdt)2(H2O)2]SiF6·CH3CN·2H2O. A sluggish hydrolysis of …
Increased conformational rigidity of humic substances by oxidative biomimetic catalysis
2005
A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed …
Conformational investigation of α,β‐dehydropeptides. XV: N‐acetyl‐α,β‐dehydroamino acid N ′N ′‐dimethylamides: conformational properties from infrare…
2005
The FTIR spectra were analysed in the region of the nu(s)(N-H), AI(C=O) and nu(s)(Calpha=Cbeta) bands for a series of Ac-DeltaXaa-NMe2, where DeltaXaa = DeltaAla, (Z)-DeltaAbu, (Z)-DeltaLeu, (Z)-DeltaPhe and DeltaVal, to determine a predominant solution conformation of these alpha,beta-dehydropeptide-related molecules. Measurements were taken in CCl4, DCM and MeCN solutions. In the same way, spectra of saturated analogues Ac-Xaa-NMe2, where Xaa = Ala, Abu, Leu, Phe and Val, were investigated. To help interpret the spectroscopic results, conformational maps were calculated by the B3LYP/6-31+G** method. Also, the relative energies of all conformers of the dehydro compounds in vacuo as well as…
Conformational investigation of α,β‐dehydropeptides Part VI. Molecular and crystal structure of benzyloxycarbonylglycyl‐(Z )‐dehydrophenylalanine
1994
The structure of a peptide containing C-terminal dehydrophenylalanine, Z-Gly-(Z)-delta Phe (C19H18N2O5, MW = 354) was determined from single-crystal X-ray diffraction data. Needle-shaped crystals were grown from a 1:1 mixture of methanol-acetone in the monoclinic space group P2(1) with a = 14.717(4), b = 4.941(2), c = 12.073(4) A, beta = 103.72(4) degrees; V = 852.86(8) A3, Z = 2 and Dc = 1.32 g cm-3. The structure was solved by direct methods using SHELXS-86 and refined to a final R-index of 0.032 for 1714 observed reflections. The peptide adopts a conformation folded at the glycine residue, and principal torsion angles are omega 0 = -167.6(2) degrees, phi 1 = -71.8(3) degrees, psi 1 = -31…
Methionine in a protein hydrophobic core drives tight interactions required for assembly of spider silk
2019
Web spiders connect silk proteins, so-called spidroins, into fibers of extraordinary toughness. The spidroin N-terminal domain (NTD) plays a pivotal role in this process: it polymerizes spidroins through a complex mechanism of dimerization. Here we analyze sequences of spidroin NTDs and find an unusually high content of the amino acid methionine. We simultaneously mutate all methionines present in the hydrophobic core of a spidroin NTD from a nursery web spider’s dragline silk to leucine. The mutated NTD is strongly stabilized and folds at the theoretical speed limit. The structure of the mutant is preserved, yet its ability to dimerize is substantially impaired. We find that side chains of…
Polymorphism and versatile solvate formation of thiophanate-methyl
2009
The polymorphism of a fungicide, thiophanate-methyl (TM), was investigated with conventional solvent screening methods. Two polymorphs, the thermodynamically most stable form I and the less stable form II, were found. TM was also found to crystallize as a plethora of different solvates which produced mostly form II upon desolvation. The structures of form I and form II and the fourteen discovered solvates were solved by single crystal X-ray diffraction. The most stable forms were further characterized by powder diffraction, thermoanalytical (TG/DTA, DSC and thermomicroscopy) and spectroscopic (IR, Raman, ¹³C CP/MAS NMR) methods. peerReviewed
The first copper(I)-olefin complexes bearing a 1,3,4-oxadiazole core: Alternating-current electrochemical crystallization, X-ray experiment and DFT s…
2017
By means of alternating-current electrochemical technique, four new π-complexes, namely [Cu2(C11H10N2OS)2Br1.91Cl0.09] (1), [Cu(C11H10N2OS)NO3] (2), [Cu2(C11H10N2OS)2(H2O)2](BF4)2 (3) and [Cu2(C11H10N2OS)2(H2O)2](ClO4)2 (4), were obtained using copper(II) salts and the 2-(allylthio)-5-phenyl-1,3,4-oxadiazole (C11H10N2OS) ligand. The metal and halogen centers in 1 form Cu2X2 dimers; the N-atom from the oxadiazole ring and the Cdouble bond; length as m-dashC bond of the allyl group from the same ligand complete the copper coordination environment, giving [Cu(C11H10N2OS)X]2 isolated fragments. The ligand plays the same chelating role in 2, whereas the O (NO3) atom occupies the third position i…
Orientation of the electric field gradient and ellipticity of the magnetic cycloid in multiferroic BiFeO3
2016
This work was supported by Uniwersytet Pedagogiczny.