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1.
Abstract The α-heterosubstituted N, N?diethylacetamides(1–8) cis/gauche conformations population ratio have been estimated through the analysis of the carbonyl group stretching vibration in the carbon tetrachloride and in chloroform. The substituent steric properties determine the cis/gauche ratio which decreases as the substituent size increases. For most of the studied amides, the gauche rotamer carbonyl band exhibits larger shifts to lower frequencies than in the corresponding α-heterosubstituted propanones1, but for the α-chloro-(4) and for the α-bromo-N,N?diethylacetamide(5) a reverse trend is observed. This behavior can be related to changes in the πC=O C—X Dihedral angle, an hyperconjugative effect being sugges ted to explain the frequency shifts of the gauche rotamers. 相似文献
2.
The method described previously for the calculation of the X spectrum for spin systems of of the XnAA′Xn′ type is extended by means of magnetic equivalence factoring to cases in which the long-range coupling constant Jx is non-zero. This coupling is treated as a first-order perturbation to the energy levels obtained when Jx =0, and it is found that Jx may be measured directly from the separations between easily identified lines in the spectrum. A detailed account of the X 3 AA′X 3′ system is given, and the N.M.R. spectrum of fluoro-N,N′-dimethyl-1,3,2,4-diazadiphosphetidine is analysed. The spectral parameters obtained are discussed. A computer programme which calculates the spectra of systems involving magnetic equivalence is used to examine the validity of the approximations in the method. 相似文献
3.
A. Aït-Bahammou F. Hartmann-Boutron C. Meyer Y. Gros Y. Berthier 《Hyperfine Interactions》1986,28(1-4):577-580
Hydrides of Intermetallic compounds have been the object of many studies because of their potential applications/1/. Recent papers were devoted to the problem of interstitial site occupation in connection with H-H exclusion rule (dH–H > 2.1 A). The present work deals with ErFe2HX, which has been investigated both by57Fe Mössbauer Effect and by167Er N.M.R. Previous studies were limited to X 2, 3.5, 4.1. Here five values of x (1.45, 1.6, 1.84, 2.6, 3.3) are considered, in order to obtain information on hydrogen location, filling and diffusion as a function of x, and also on hydrogen contribution to the electric field gradient (E.F.G.) and crystalline field at the Rare Earth. 相似文献
4.
《Journal of magnetism and magnetic materials》2001,232(3):155-160
The structure and magnetic properties of γ′-(Fe1−xSnx)4N samples have been studied using X-ray diffraction and 57Fe Mössbauer spectroscopy. It has been shown that the single-phase (Fe1−xSnx)4N compounds can be prepared in the composition range of 0.0⩽x⩽0.3, which have the similar structure as γ′-Fe4N The lattice parameter with the increase of Sn concentration can be well fitted with two linear relationships a0(x)=3.795+0.019x (with x⩽0.10 ) and a0(x)=3.797+0.228(x−0.10) (with 0.1⩽x⩽ 0.3). The fitting results of Mössbauer spectra indicate that the hyperfine parameters have the same changing tendency with lattice parameter, and the Sn atoms have a preference to be located at the corner site. 相似文献
5.
Zhang Ye Hao Yuying Meng Weixin Xu Huixia Wang Hua Xu Bingshe 《Applied Physics A: Materials Science & Processing》2012,106(3):709-715
The electroplex between (2-(4-trifluoromethyl-2-hydroxyphenyl)benzothiazole) zinc [Zn(4-TfmBTZ)2] as an electron-acceptor and N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) as an electron-donor was
characterized by bilayer, blend, and multilayer quantum-well (MQW) device, respectively. The blend composition and quantum-well
number are effective parameters for tuning electroluminescence color. White light with high color purity and color rendering
index (CRI) was observed from these devices based on Zn(4-TfmBTZ)2/NPB. Moreover, the blend and MQW devices all exhibit high operation stability, hence excellent color stability. For the device
with 5 mol% NPB in blend layer, its Commission International Del’Eclairage (CIE) coordinate region is x=0.28–0.31, y=0.33–0.35 and CRI is 83.3–91.2 at 5–9 V. For MQW structure device with NPB of 60 nm thickness, its CIE coordinate region
is x=0.29–0.32, y=0.31–0.34 and CRI=87.9–92.5 at 10–15 V. Such high color stability and purity and CRI, being close to ideal white light, are
of current important for white OLED. 相似文献
6.
《光谱学快报》2013,46(3):319-342
Abstract The application of nuclear magnetic resonance (NMR) spectroscopy, hyphenated NMR, and diffusion‐ordered spectroscopy (DOSY) to the characterization of mango juice, as an example of a complex food mixture, is described. The compositional changes taking place as a function of ripening were followed, and selected metabolites were quantified by integration of the corresponding NMR peaks. In this way, an overall view of the metabolite changes is obtained, enabling the study of the biochemical mechanisms involved in the ripening process. More than 50 compounds were identified by 1D‐ and 2D‐NMR, but many ambiguous assignments remain due to spectral overlap or insufficient coupling information. The use of Liquid Chromatography (LC‐NMR) and LC‐NMR/Mass Spectrometry (MS) enables a fuller characterization of the soluble pectin fraction to be made; its dependence on ripening stage is discussed. Finally, DOSY adds information on the Mr of many metabolites, including the pectin fractions of ripe and unripe mango juices, and enables further peak assignments to be made. 相似文献
7.
Vikas S. Patil Vikas S. Padalkar Abhinav B. Tathe Vinod D. Gupta N. Sekar 《Journal of fluorescence》2013,23(5):1019-1029
Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and 1,2-phenelenediamine, 2-aminophenol, and 2-aminothiophenol respectively. The synthesized 2-(2′,4′-dihydroxyphenyl) benzimidazole, benzoxazole and benzothiazole are fluorescent and the emission characteristic are very sensitive to the micro-environment. They show a single absorption and dual emission with large Stokes shift originating from excited state intramolecular proton transfer. The absorption-emission characteristics of all these compounds are studied as a function of pH. The change in the electronic transition, energy levels, and orbital diagrams of synthesized compounds were investigated by the molecular orbital calculation and were correlated with the experimental spectral emission. Experimental absorption and emission wavelengths are in good agreement with those predicted using the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) [B3LYP/6-31G(d)]. Figure
Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and o- amino aromatics. Single absorption and dual emission are the interesting properties of the synthesized compounds. 相似文献
8.
Four racemic mixtures were synthesized and characterized. Their mesomorphic properties, such as phase transitions temperatures and enthalpies, were measured by a polarizing optical microscope and differential scanning calorimetry. The influence of one racemic mixture on the properties of the OAFLC mixture W-1000 was studied. The results show a wide temperature range of the SmCA* phase in this new mixture. The helical pitch was measured by spectrophotometry method. The electro-optical properties of the mixture were also presented and discussed. 相似文献
9.
A. A. Volod’kin V. N. Erokhin E. B. Burlakova G. E. Zaikov S. M. Lomakin 《Russian Journal of Physical Chemistry B, Focus on Physics》2013,7(1):44-49
Sodium (1) and potassium (2) 1-(carboxy)-1-(N-methylamide)-2-(3′,5′-di-tert-butyl)-4-hydroxyphenyl)-propionates form crystal hydrates, which exist as both monomers and dimers. Quantum-chemical calculations in the PM6 approximation are used to determined the enthalpies of formation ?H f po , thermal enthalpy H po, and entropy S po of the monomers and dimers, which are indicative of the possibility of existence of the dimers of propionates of alkali metals. The biological activity of these compounds in animal and plants is demonstrated to be dependent on their concentrations. Compounds 1 and 2 turned out to be efficient in the treatment of burn injuries, cancer, and radiation damage (in vivo and in vitro), as well as in promoting the growth of cereal plants. 相似文献
10.
N. K. Singh M. Singh P. Tripathi A. K. Srivastava M. J. K. Thomas 《Hyperfine Interactions》2008,185(1-3):133-137
A new series of iron(III) complexes [Fe(L1)(HL1)], [Fe(L1)Cl]; [H2L1 = N′-(2-methoxythiobenzoyl)pyridine-2-carbohydrazide], [Fe(L2)(acac)], [Fe(HL2)2Cl]; [H2L2 = N′-(4-methoxythiobenzoyl)pyridine-2-carbohydrazide] and [Fe(L3) (acac)]; [H2L3 = N′-(2-hydroxythiobenzoyl)pyridine-2-carbohydrazide] were prepared by stirring/refluxing/mixing the respective ligand with FeCl3/Fe(acac)3 in chloroform/methanol. All the compounds were characterized by elemental analyses, magnetic susceptibility, IR, UV and Mössbauer spectral data. The complexes posses high/ low spin state and have tetrahedral/octahedral geometry. 相似文献
11.
Analytical expressions have been derived for the transition frequencies and intensities of a partially oriented group of deuterium nuclei with symmetry of the permutation group. Using d 3-acetone, CD3COCH3, dissolved in a nematic solvent, as an example, it is shown how 1H?{2H} double resonance experiments can be used to determine the relative signs of dipolar and quadrupolar interactions. The magnitude of the quadrupole coupling constant of the 2H nuclei in CD3COCH3 is determined. 相似文献
12.
Infrared transmission, Reflectance-Absorption (RA) and Ultra-Violet (UV) spectra were measured for mono-and multi-layers Langmuir-Blodgett (LB) films of 4-[4′-(4″-decyIoxy phenylazo)naphthloxy] butyl trimethylammonium bromide formed with SDS to study the molecular orientation and aggregation. The results indicate that the compound do not aggregate in the LB films, and the alkyl tail is nearly perpendicular to the substrate surface and the chromorphore part adopts trans-zigzag conformation. These results also suggest that the molecular orientation and aggregation are not depend upon the number of monolayers The comparison of infrared transmission and RA spectra indicates that the hydrocarbon chain is nearly perpendicular to the substrate surface, but the two rings in the chromophore part are tilted considerably from the surface normal. 相似文献
13.
《Journal of Magnetic Resonance (1969)》1981,42(1):28-37
Nuclear magnetic resonance linewidth and spin-lattice relaxation time T1 were measured for 4-methoxybenzylidene-4′-n-butylaniline (MBBA) and N-(2-hydroxy-4-methoxybenzylidene)-4′-n-butylaniline )OHMBBA) in their liquid, nematic, undercooled nematic, and glassy nematic liquid crystal states as well as in the stable crystalline states. In the case of OHMBBA, the motional narrowing occurs in three steps corresponding to excitation of end-group reorientations, self-diffusion, and molecular tumbling. T1 of OHMBBA in the nematic and undercooled nematic state has two minima at 264 K (24 ± 4 msec) and at 140 K (22.0 ± 0.5 msec); the motions responsible for the minima are the self-diffusion and the end-group reorientations with the activation energies 29 ± 1 J mole−1 and 5.8 ± 0.2 kJ mole−1 respectively. Analogous results were obtained for MBBA. Some measurements were also made for p-azoxyanisole for the sake of comparison. The effect of external magnetic field on the formation of the glassy state was examined. 相似文献
14.
Absorption and fluorescence spectra of 2-dimethylamino-9(4'-dimethylamino)phenyl-9-fluorenol have been studied in different solvents. The fluorescence spectra at various temperatures show the excitation wavelength dependence. The spectroscopic data are compared with the results of the quantum chemical calculation obtained using PM3 and INDO/S methods. The fluorescence decay curves of the molecule under study can be only satisfactorily fitted by a biexponential function. The steady state and time resolved spectroscopy studies as well as the theoretical calculation confirm that in methylcyclohexane and ethyl acetate solutions always two absorbing and emitting species exist, namely rotamers alpha and beta in the ground and excited states. 相似文献
15.
Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form –COO−. Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form –COOH and the cationic form –COOH2+. The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1′-oxo-2′,2′,6′,6′-tetramethyl-4′-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO.). 相似文献
16.
Samy A. El-Daly Khalid A. Alamry Abdullah M. Asiri Mahmoud A. Hussein 《Journal of luminescence》2012,132(10):2747-2752
The photophysical properties such as electronic absorption, molar absorptivity, emission spectra, fluorescence quantum yield and fluorescence lifetime of N,N′-bis(4-pyridyl)-3,4:9,10-perylene bis(dicarboximide) (BPPD) have been measured in different solvents. Both electronic absorption and fluorescence spectra are not sensitive to medium polarity, while the fluorescence quantum yield (?f) is solvent dependent. The ground state geometry has been computed by using density functional theory (DFT), the transition from HOMO to LUMO from perylene core with maximum absorption at 512 nm and HOMO–LUMO energy difference equal 2.53 eV. BPPD dye undergoes molecular aggregation to dimmer or higher aggregates in dimethyl sulfoxide (DMSO). Crystalline solids of BPPD gives excimer-like emission at 676 nm. The fluorescence quenching of BPPD is also studied using hydrated ferric oxide nanoparticle (FeOOH), and the Stern–Volmer rate constants (Ksv) were calculated as 8×106 and 9.2×106 M?1 in ethanol and ethylene glycol, respectively. 相似文献
17.
《Solid State Communications》1987,63(7):635-639
Compounds of the form (M1−xM′x)2CuO4−δ and related compounds where M and M′ are Y, various rare earths from La to Lu, and the alkaline earths Sr and Ba, have been investigated in connection with high temperature superconductivity. High temperature superconductivity is confirmed for the system (La1−xBax)2CuO4−δ, (La1−xSrx)2CuO4−δ and (Y1−xBax)2CuO4−δ with superconducting transition temperature Tc onsets of 30 K, 38 K and 90 K, respectively. We have found that the related systems (Eu1−xBax)2CuO4−δ and (Sm1−xBax)2CuO4−δ also exhibit high temperature superconductivity with Tc onsets of 95 K and 65 K, respectively. The highest Tc onset observed in this investigation was 97 K for a sample with the nominal composition of the spinel structure Y0.33Ba0.67Cu2O4−δ. Measurements of the specific heat C as a function of temperature T on a La0.8Sr0.2CuO4−δ sample reveal a break in slope in the C/T vs T curve at the Tc midpoint, but no clearly discernable jump in C at Tc. A linear term ≈ λ′T in C was observed at low temperature in the superconducting state. 相似文献
18.
A highly sensitive method is proposed to determine copper(II) ions by forming a stable complex through their interaction with
4-(2′-benzothiazolylazo)-salicylic acid (BTAS) at room temperature and pH of about 5.0. The complex gave a maximum absorption
at λ = 485 nm with a molar absorptivity coefficient of 2.35·104 l/(mol·cm). The linear range for the copper determination is 0.63–5.04 mg/l. The method can be applied to determine copper
ions in different biological specimens like some drugs and water samples. 相似文献
19.
Abstract Dynamic and structural features of N-Isopropyl-N- {3-[4(4-Methoxybenzoylamino)Phenoxy]-2-Hydroxypropyl} Ammonium Chloride in [2H6]DMSO were investigated by measuring 13C and 1H spin-lattice relaxation rates and 13C- {1H} and 1H- {1H} n.O.e. Correlation times for main and internal reorientational motions were interpreted in terms of internal rotation around the two planal axes. Selective and double-selective 1H spin-lattice relaxation rates were measured, wherefrom relevant proton-proton intramolecular distances were calculated. It was shown that the β1? blocking agent assumes a preferred conformation where extensive intramolecular H-bonding prevents segmental motion along the quaternary ammonium sidechain. 相似文献
20.
Electron spin resonance (ESR) spectra caused by a stable trapped H atom, a Dy3+ ion, and a PO4 unit were observed in X-ray-irradiated dysprosium-doped β-tricalcium phosphate (β-Ca3(PO4)2:Dy, β-TCP:Dy) phosphor. The ESR spectrum of the H atom in the X-ray-irradiated β-TCP:Dy phosphor was slightly different from
that of nondoped X-ray-irradiated β-TCP, suggesting that the Dy3+ spin state has a significant effect on the relaxation time of electron spins. The electron spin echo of the H atom was observed
in the X-ray-irradiated β-TCP but not in the corresponding X-ray-irradiated β-TCP:Dy phosphor.
Authors' address: Kouichi Nakashima, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Aoba-ku,
Sendai 980-8577, Japan 相似文献