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1.
Fabrication and Magnetic Properties of Co-Doped TiO2 Powders Studied by Nuclear Magnetic Resonance
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Co0.04 Ti0.96O2 powders are fabricated by sol-gel method. The structure and magnetic properties are investigated under different annealing conditions systematically with emphasis on the influence of oxygen pressure. Pure anatase structure was acquired for all the samples annealed at 450℃ for one hour. The samples annealed in air exhibit evident room-temperature ferromagnetism (RTFM) with a small magnetic moment of 0.029μB per Co atom and coercivity Hc of 26 Oe, while the samples annealed in vacuum have strong RTFM with a larger magnetic moment of 1.18μB per Co atom and Hc of 430 Oe. The zero-field spin echo nuclear magnetic resonance spectrum of ^59Co is obtained to prove the existence of Co dusters in the latter samples, implying that the Co dusters are responsible for the strong RTFM in the samples annealed in vacuum. No Co cluster could be observed using both XPS and NMR techniques in the samples annealed in air, implying that the RTFM found in these sample sis intrinsic. 相似文献
2.
《光谱学快报》2013,46(5-6):461-475
The 1H‐ and 13C‐NMR spectra of 1‐β‐d‐glucopyranosyl‐1,2,3‐triazole‐4,5‐dimethyl carboxylate, 1‐β‐d‐glucopyranosyl‐1,2,3‐triazole‐4,5‐dicarboxamide, ‐dialkylcarboxamide‐N‐nucleosides 4–18, and 6‐amino‐4H‐1‐(1‐β‐d‐glucopyranosyl)‐8‐hydroxy‐1,2,3‐triazolo[4,5‐e][1,3]‐diazepin‐4‐one 19 had been studied. Resonance signals and anomeric configurations were assigned by homo‐ and heteronuclear two dimensional methods (DQF‐COSY, HSQC, HMBC, HMQC, ROESY). 相似文献
3.
Abstract Two melampolide-type sesquiterpene lactones, enhydrin and 2,′ 3′-dehydromelnerin A, were isolated from a Louisiana population of Polymnia uvedalia. Their 13C NMR spectra were assigned using 13C-1H correlation, DEPT and COLOC experiments. The molecular structure of enhydrin was established by single crystal X-ray diffraction. 相似文献
4.
《光谱学快报》2013,46(4-5):477-485
Abstract The 1H‐ and 13C‐NMR spectra of some substituted stilbenes and chalcones were assigned unambiguously on the basis of a combination of homo‐ (COSY) and heteronuclear (HETCOR) two‐dimensional methods, the chemical shifts, as well as spin‐coupling constants. The Aik empirical parameters of the –O–C(S)–N(CH3)2, –S–C(O)–N(CH3)2, and –SH group were calculated to help predict the chemical shifts of substituted stilbenes, 4′‐nitrostilbenes, and chalcones. The 1H‐ and 13C‐NMR spectra have been shown to be able to differentiate between the isomers of O‐stilbenyl (4, 5) and S‐stilbenyl N,N‐dimethylthiocarbamates (7, 8) as well as O‐chalconyl (6) and S‐chalconyl N,N‐dimethylthiocarbamates (9). 相似文献
5.
《光谱学快报》2013,46(5):437-456
Abstract The structures of new isomeric 2‐alkoxycarbonylalkylthio‐ and 2‐alkoxy‐ carbonylalkylthio‐1‐alkoxycarbonylalkyl‐6‐aminouracils (1–21) have been established on the basis of the 1H NMR and 13C NMR spectroscopic data. The 1H NMR and 13C NMR spectra of 1–21 have been fully assigned by a combination of two‐dimensional experiments [heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond correlation (HMBC)]. The 13C NMR spectra have been shown to be able to differentiate between isomers. 相似文献
6.
《光谱学快报》2013,46(5):493-516
Abstract The Diels–Alder adducts, 3a–e, of phencyclone, 1, have been prepared from a series of N‐n‐alkylmaleimides, 2, with medium chain‐length n‐alkyl groups. The maleimides were obtained by cyclodehydration of the N‐n‐alkylmaleamic acids, 4, formed from reaction of maleic anhydride with the corresponding n‐alkylamines. The five adducts prepared included derivatives from n‐heptyl, 3a; n‐octyl, 3b; n‐nonyl, 3c; n‐decyl, 3d; and n‐dodecyl, 3e. The NMR spectra of the adducts were studied in CDCl3 at ambient temperatures at 300 MHz for proton and 75 MHz for carbon‐13, with full proton assignments achieved by high‐resolution COSY45 spectra for the aryl and the alkyl regions. Slow exchange limit (SEL) spectra were observed for both 1H and 13C spectra showing slow rotation on the NMR timescales of the unsubstituted bridgehead phenyl groups. Endo Diels–Alder adduct stereochemistry was supported by striking magnetic anisotropic shielding effects in the 1H spectra of the alkyl groups, with the NCH2 CH 2 signal of each adduct appearing upfield of tetramethylsilane (TMS) at ca. ?0.32 ppm. Proton NMR spectra for precursor maleamic acids and maleimides are reported, with some solvent effects found (CDCl3 vs. d 6‐acetone) for the carbon‐bound HC?CH protons of 4. Ab initio molecular modeling calculations at the Hartree‐Fock level using the 6‐31G* basis set have been performed for two key conformers of the phencyclone adduct of N‐n‐octylmaleimide, as a representative structure for these hindered adducts, to estimate geometric parameters for the adduct. A syn conformer, with the alkyl chain directed into the adduct cavity, was found to be ca. 0.23 kcal/mol lower energy than an anti conformer (in which the alkyl chain was directed away from the phenanthrenoid moiety). 相似文献
7.
Realization of the Fredkin Gate by Three transition Pulses in a Nuclear Magnetic Resonance Quantum Information Processor
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We have experimentally realized the Fredkin gate with only three transition pulses in a solution of alanine.It appears that no experimental realization of the Fredkin gate with fewer pulses has been reported yet.In addition,the simple structure of our scheme makes it easy to implement in experiments. 相似文献
8.
9.
Isotope Effects by Comparing 1H‐ and 2D‐NMR Spectra of 9,9′‐Bisbicyclo[4.3.0]‐cyclonona‐2,4,7‐triene
《光谱学快报》2013,46(4-5):487-496
Abstract Inverse secondary kinetic isotope effects are determined for the dimerization of all‐cis‐cyclononatetraenyl radical, 1, to its corresponding dimer, all‐cis‐9,9′‐bicyclonona‐1,3,5,7‐tetraene, 2, (step 1, k H/k D=0.5), and cyclization of the latter to 9,9′‐bisbicyclo[4.3.0]cyclonona‐2,4,7‐triene, 3 (step 2, k H/k D=0.75). These results are obtained by comparison of 1H‐ and 2D‐NMR spectra of 3 and employment of a simple statistical method for acquiring kinetic data. This new strategy appears superior to conventional methods in being fast, simple, and less expensive. 相似文献
10.
Rhodamine derivatives are popular, photostable fluorophores that are used in a number of fluorescent based techniques, including
fluorescence correlation spectroscopy (FCS). Indeed, in FCS, both rhodamine 6G (R6G) and rhodamine 110 (R110) are used as
calibration standards to determine the dimensions of the instrument confocal volume. In spite of a requirement for precise
values of the diffusion coefficients, literature values are scarce and vary over an order of magnitude. In this paper, the
diffusion coefficients of four rhodamine fluorophores (rhodamine 6G (R6G), rhodamine B (RB), rhodamine 123 (R123), rhodamine
110 (R110)) were determined by pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectrometry and then validated
by comparison with fluorescence correlation spectroscopy. With the objective of validating the FCS calibration, diffusion
coefficients of several dextrans and a polystyrene nanoparticle were also determined and compared with literature values or
theoretical values that were based upon the Stoke–Einstein equation. The work presented here lead us to conclude that the
diffusion coefficients for R6G and R110 have generally been underestimated in the literature. We propose revised values of
4.4 × 10−10 m2 s−1 for R110 and 4.0 × 10−10 m2 s−1 for R6G. Using the revised D value for R110 to calibrate the FCS instrument, diffusion coefficients have then been systematically determined for different
conditions of pH, ionic strength and concentration. To correct for differences due to solvent effects (D2O vs. H2O), an isotopic correction factor, of 1.23, was determined from both FCS and from the solvent auto-diffusion coefficients obtained by NMR. 相似文献
11.
We report on the magnetic properties and magnetocaloric effects of Mn5Ge3-xGax compounds with x=0.1,0.2,0.3,0.4,0.6 and 0.9. All samples crystallize in the hexagonal Mn5Si3-type structure with space group P63/mcm and order ferromagnetically.The Curie temperature of these compounds decreases with increasing x, from 306K (x=0.1) to 274K (x=0.9).The average Mn magnetic moments increases with increasing Ga content,reaching a maximum value at x=0.6.The magnetic entropy changes in these compounds are determined from the temperature and field dependence of the magnetization using the thermodynamic Maxwell relation.The Ga substitution has two kinds of influence on the magnetocaloric effect (MCE) of Mn5Ge3.One is that the magnitude of the magnetic entropy change decreases,the other is that the MCE peak becomes broadened. 相似文献
12.
A new daunorubicin has been synthesized and structurally characterized. The interaction of native calf thymus DNA (ctDNA) with 3′-azido-daunorubicin thiosemicarbazone (ADNRT) was investigated under simulated physiological conditions by multi-spectroscopic techniques, viscometric measurements and molecular modeling study. It concluded that ADNRT could intercalate into the base pairs of ctDNA, and the fluorescence quenching by ctDNA was static quenching type. Thermodynamic parameters calculated suggested that the binding of ADNRT to ctDNA was mainly driven by hydrophobic interactions. The relative viscosity of ctDNA increased with the addition of ADNRT, which confirmed the intercalation mode. Furthermore, molecular modeling studies corroborate the above experimental results. 相似文献
13.
N. I. Garbuz L. P. Solovei N. V. Kovganko Yu. G. Chernov 《Journal of Applied Spectroscopy》2002,69(1):58-61
The intramolecular hydrogen bond in steroid 5hydroxy6ketones and 5hydroxy6ketoximes of the stigmastane series has been investigated by the method of IR spectroscopy. It is shown that 5hydroxy groups in cisA/Bsteroids are linked by the intramolecular hydrogen bond with polar substituents at C3 and C6. These hydrogen bonds are lacking in corresponding transA/Bsteroids. According to the IR spectra, intramolecular associates of polymer type are formed in 5hydroxy6hydroxyminosteroids. 相似文献
14.
《Journal of Molecular Spectroscopy》1986,118(2):363-382
The Asundi system (a′3Σ+-a3Π) of 13C16O has been studied between 3500 and 12 000 cm−1 by high-resolution Fourier transform spectroscopy. The 10 bands, 0-0, 0−1, 1−0, 1−1, 1−2, 2−0, 2−1, 3−0, 4−0, and 4−2, were analyzed taking into account the strong perturbations appearing in the a′3Σ+ (v = 0,…,4) levels. Accurate perturbation parameters were obtained for all interacting states. 相似文献
15.
Wenzhong Wang 《Journal of Macromolecular Science: Physics》2013,52(6):1081-1092
To investigate the influences of side chains and cross‐linking network on the packing fashion and the formation of aggregates and excimers of poly(p‐phenyleneethynylene)s (PPEs) chains in the solid state, a series of cross‐linkable unsubstituted oligo (p‐phenyleneethynylene)s (OPEVs) and alkoxy‐substituted PPEs (EO‐PPEVs) with vinyl end‐groups were synthesized and characterized. By a thermal cross‐linking reaction, cross‐linked polymers were obtained. The oligomer chains in the cross‐linked polymers containing no residual vinyls are packed randomly, forming no aggregates or excimers; however, aggregates and excimers exist in the cross‐linked polymers if they contain residual vinyls. The chains of EO‐PPEVs with sterically hindered side chains form aggregates in films. The network, leading to a pronounced increase of the film photoluminescence quantum yields, can depress these aggregates. These EO‐PPEVs are fully processable and can become insoluble in normal organic solvents after thermal curing; therefore, they are favorable candidates as active layers for fabrication of high performance multilayer devices. 相似文献
16.
《光谱学快报》2013,46(4):421-436
Abstract Phencyclone, 1, reacted with N‐(2,6‐dimethylphenyl)maleimide, 2a; with N‐(2,6‐diethylphenyl)maleimide, 2b; and with N‐(2,6‐diisopropylphenyl)maleimide, 2c, respectively, to yield the corresponding Diels–Alder adducts, 3a–c. The adducts were extensively characterized by NMR (7 T) at ambient temperatures using one‐ and two‐dimensional (1D and 2D) proton and carbon‐13 techniques for assignments. Slow exchange limit (SEL) spectra were observed, demonstrating slow rotations on the NMR timescales, for the unsubstituted bridgehead phenyl groups [C(sp3)–C(aryl sp2) bond rotations] and for the 2,6‐dialkylphenyl groups [N(sp2)–C(aryl sp2) bond rotations]. Substantial magnetic anisotropic shifts were seen in the adducts. For example, in the N‐(2,6‐dialkylphenyl) moieties of the adducts, one of the alkyl groups is directed “into” the adduct cavity, toward the phenanthrenoid portion, and these “inner” alkyl proton NMR signals were shifted upfield. Thus, in CDCl3, the “inner” methyl of adduct 3a exhibits a proton resonance at ?0.13 ppm, upfield of tetramethylsilane (TMS); the “inner” ethyl group signals from 3b appear at 0.026 ppm (CH2, quartet), and ?0.21 ppm (CH3, triplet); and the “inner” isopropyl group from 3c is seen at ?0.06 ppm (methine, approx. septet) and ?0.39 ppm (CH3, doublet). Proton NMR of the crude N‐(2,6‐dialkylphenyl)maleamic acids (used as precursors of the maleimides, 2a–c) exhibited two sets of AB quartet signals, suggesting possible conformers from hindered rotation in the amide groups about the HN–C?O bonds. 相似文献
17.
V. V. Kveder É. A. Shteinman R. N. Lyubovskaya S. A. Omel’chenko Yu. A. Osip’yan 《JETP Letters》2001,74(8):422-424
The EPR and static magnetic susceptibility of the crystalline molecular complex between fullerene C60 and an organic donor 9,9′-trans-bis(telluraxanthenyl) (BTX) have been measured as functions of temperature. At temperatures T above 130 K, the samples exhibit anomalously high magnetic susceptibility exceeding the values calculated under the assumption that each molecule bears one paramagnetic spin 1/2. A very intense magnetic resonance signal is also observed in the samples in the region of high g factors (g>4.5). This allows the suggestion that the samples under study possess ferromagnetism (or superparamagnetism). The EPR signal and magnetic susceptibility sharply decay almost to zero as the temperature decreases below 100–120 K. It is supposed that electron transfer from donor molecules BTX to C60 molecules takes place at temperatures above 110 K. This electron transfer generates electron spins in the system, whereas the anomalously high magnetism is due to ferromagnetic correlations in the system of these spins. 相似文献
18.
We have carried out a nonempirical quantumchemical calculation with full optimization of the geometry of all theoretically possible tautomeric forms of 3formyltetrinic acid (FTRA) according to the Møller–Plesset secondorder perturbation theory with the use of a 6–31G(d) double zeta basis set. The correlation corrections to the total energy of molecules for optimized geometric configurations were calculated in the 631G(d,p) basis. All the possible tautomeric forms of FTRA and the harmonic vibrational frequencies were also calculated within the density functional theory (DFT) with the use of the Perdew–Burke–Ernzerhof (PBE) functional in a threeexponent basis. It is shown that FTRA in vapors (in the perfect gas approximation) exists in the form of a mixture of three enol forms, among which two exoforms predominate. The frequencies and forms of normal vibrations for each cisenol tautomer in the region of vibrations of ketogroups and double bonds differ widely, which permits identification of the tautomers present in the mixture. The possible mechanisms of enolenol transformations of 3acyltetrinic acids are discussed. 相似文献
19.
Ae Ran Lim 《Applied magnetic resonance》2012,42(1):89-100
The physical properties and phase transitions of Rb2CuCl4·2H2O and Cs2MnCl4·2H2O crystals were investigated by performing 85Rb, 87Rb, and 133Cs nuclear magnetic resonance relaxation analyses. The temperature dependences of the spectra and the spin–lattice relaxation
times T
1 near T
C are related to changes in the symmetry of the octahedrons consisting of four Cl− ions and two water molecules around Rb+ or Cs+; the forms of these octahedrons are disrupted by the loss of H2O. The difference between the relaxation times of the two crystals is possibly due to the difference between the electron
structures of the Cu and Mn ions. Cu2+ has nine valence electrons in its 3d orbital, whereas Mn2+ has five valence electrons in its 3d orbital. 相似文献