共查询到20条相似文献,搜索用时 15 毫秒
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Zied Hassen 《Journal of fluorine chemistry》2003,121(2):177-183
Ten phosphorylated β-hydrazones of structure R2P(O)C(NNHRF)CHR2′ were prepared in 54-91% yield by heating the allenes R2P(O)CHCCR2′ with fluorinated hydrazines H2NNHRF in chloroform or methanol [R=Ph, OCH2C(Me)2CH2O or OCH2C(Me)(Pr)CH2O, R′=H or Me and RF=CH2CF3 or C6F5]. Two cyclohexyl derivatives were prepared similarly from R2P(O)CHCCy. The triphenyl derivatives Ph2P(O)CH2C(NNHCH2CF3)Ph and Ph2P(O)CH2C(NNHC6F5)Ph were made in 91 and 68% yield by heating the ketones Ph2P(O)CH2C(O)Ph with an ethanol solution of the corresponding hydrazines. The stereochemistry of the hydrazones was determined by multinuclear NMR experiments. Compounds with C(NNHRF)Me groups exist as a mixture of Z and E isomers, with the Z form predominating (fluorinated group syn to phosphorus). Those with C(NNHRF)CHMe2, C(NNHRF)Cy or C(NNHRF)Ph groups were formed selectively, the Z isomers being the only products. The results are explained by steric hindrance, the bulkier isopropyl, cyclohexyl or phenyl group disfavouring the E configuration. , , , NMR data, coupling constants and IR data are reported. 相似文献
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A ferroelectric crystal (C3N2H5)5Sb2Br11 has been synthesized. The single crystal X-ray diffraction studies (at 300, 155, 138 and 121 K) show that it is built up of discrete corner-sharing bioctahedra and highly disordered imidazolium cations. The room temperature crystal structure has been determined as monoclinic, space group, P21/n with: , and and β=96.19°. The crystal undergoes three solid-solid phase transitions: ) discontinuous, continuous and discontinuous. The dielectric and pyroelectric measurements allow us to characterize the low temperature phases III and IV as ferroelectric with the Curie point at 145 K and the saturated spontaneous polarization value of the order of along the a-axis (135 K). The ferroelectric phase transition mechanism at 145 K is due to the dynamics of imidazolium cations. 相似文献
4.
Raji Raveendran 《Journal of organometallic chemistry》2010,695(4):630-633
Reactions of [Ru(PPh3)3Cl2] with 2-(benzylimino-methyl)-4-R-phenol (HRL, R = H, Cl, Br and OMe) in boiling methanol in presence of triethylamine afford ruthenium(II) complexes of general formula [Ru(RL)(PPh3)2(CO)Cl] in 57-64% yield. Microanalysis, spectroscopic (infrared, electronic and NMR) and cyclic voltammetric measurements have been used for the characterization of the complexes. Crystal structures of two representative complexes have been determined by X-ray crystallography. The carbonyl, the chloride, the N,O-donor RL− and the two mutually trans PPh3 molecules assemble a distorted octahedral CClNOP2 coordination sphere around the metal centre in each complex. The complexes display the Ru(II) → Ru(III) oxidation in the potential range 0.62-1.16 V (vs. Ag/AgCl). 相似文献
5.
The accommodation of Co in the oxygen-saturated solid-solution phase YBa2(Fe1−zCoz)3O8+w has been investigated by powder X-ray and neutron diffraction techniques, as well as by Mössbauer spectroscopy. Of the nominal composition range 0.00?z?1.00 tested, the solid-solution limit under syntheses at 950°C in is z=0.47(5). No symmetry change in the nuclear and magnetic structures is seen as a consequence of the Co substitution, and the Co atoms are distributed evenly over the two sites that are square-pyramidally and octahedrally coordinated for w=0. The oxygen-saturated samples maintain their oxygen content roughly constant throughout the homogeneity range, showing that Co3+ replaces Fe3+. Despite the nearly constant value of w, Mössbauer spectroscopy shows that the amount of tetravalent Fe slightly increases with increasing z, and this allows Co to adopt valence close to 3.00 to a good approximation. The magnitude of the antiferromagnetic moment (located in the a,b plane) decreases with z in accordance with the high-spin states of the majority Fe3+ and Co3+ ions. Bond-valence analyses are performed to illustrate how the structural network becomes increasingly frustrated as a result of the substitution of Fe3+ by the smaller Co3+ ion. A contrast is pointed out with the substitution of cobalt in YBa2Cu3O7 where it is a larger Co2+ ion that replaces smaller Cu2+. 相似文献
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To determine the diffusion of untrapped carriers in β-rhombohedral boron, we constructed a feedback pico-ammeter based on pulse integration technique. This enabled measuring deviations from the bias in a 109 Ω sample in the order of 1 nA with 0.7 ms time resolution. For the first time, we obtained the drift velocity of optically generated untrapped electron-hole pairs 106(20) cm s−1 yielding for the band-determined diffusion coefficient and for the carrier mobility . Fitting Fick's second law to the measured trap-determined dispersion of carriers yields the ambipolar diffusion coefficient D*=0.043(14) and 0.28(10) cm2 s−1 at 260 and 340 K, respectively. The thermal activation energy of 0.18 eV agrees with the well-known trapping levels in β-rhombohedral boron. 相似文献
7.
Systematics of hyperfine parameters from 237Np Mössbauer resonance data of compounds with Np in a high formal charge state are discussed with respect to electronic structure properties. In neptunyl(VI) species, we find a linear correlation between the isomer shift and the strength of quadrupole interaction. Both scale linearly with the actinide-oxygen bond length, stressing the central role of this parameter. Some compounds show paramagnetic relaxation spectra which makes their analysis difficult. The hyperfine interactions are often not rotational symmetric indicating a deviation from the simple linear O-Np-O configuration. Mössbauer spectra of NpO3·2H2O reveal that this compound should be described as a neptunyl. A comparison of hyperfine parameter systematics indicates that the Np valence electron properties in Np(VII) species are basically similar to those in Np(VI) neptunyls. 相似文献
8.
Kazuhiro Mori Ryoji Kiyanagi Kenji Iwase Takashi Sato Masaaki Sugiyama Toshiharu Fukunaga 《Journal of solid state chemistry》2006,179(11):3286-3294
In order to study the crystal structure of β‐Ca2SiO4, time-of-flight neutron powder diffraction experiments were carried out at temperatures between room temperature (RT) and 600 °C. Rietveld refinement at RT has shown that β‐Ca2SiO4 is monoclinic based on P21/n symmetry and two different types of Ca sites, Ca(1) and Ca(2). All interatomic distances within 3 Å were calculated, with the valences of Ca(1) with seven CaO bonds and Ca(2) with eight were estimated to be 1.87+ and 2+ by the Zachariasen-Brown-Altermatt formula (bond valence sum). Applying charge neutrality the two charge states of Ca in β‐Ca2SiO4 are [Ca(1)SiO4]2− and Ca(2)2+, respectively. Furthermore, the [Ca(1)SiO4]2− unit has the shortest Ca-O distance, and its length kept constant at 2.23 Å at all temperatures. In the short-range structure analysis at RT, the shortest Ca-O bond was also observed in a radial distribution function. These results imply that the [Ca(1)SiO4]2− unit has covalency on the shortest Ca-O in addition to Si-O. 相似文献
9.
Pentacoordinate complex cations of the general formula [(C6F5)2SbL3]3+ stabilized as solid salts in combination with tetraphenylborate (BPh4), tetrafluorobroate (BF4) anions, where L=DMSO, Ph3AsO, PyO, DMF, α-, β- and γ-picoline have been isolated. The newly formed complexes were characterized by elemental analysis, molar conductance measurements, solid-state IR and and NMR. From these results, a five-fold coordination around antimony was required. 相似文献
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Alexey A. Goryunkov Igor V. Kuvychko Donald L. Dick Steven H. Strauss Olga V. Boltalina 《Journal of fluorine chemistry》2003,124(1):61-64
The high temperature reaction of C60 with silver(I) trifluoroacetate followed by 500 °C sublimation and subsequent HPLC purification has led to the isolation of the five trifluoromethyl[60]fullerenes C60(CF3)n (n=2, 4, 6, 8, 10). Four of them have >90% compositional purity. Two of the compounds, C60(CF3)4 and C60(CF3)6, were obtained as C1-symmetry isomers with >90% isomeric purity, and a sample of C60(CF3)2 also contained ca. 15-20% of a Cs-symmetry isomer of C60(CF3)4. The new compounds were characterized by IR and EI mass spectrometry (all five compounds), NMR spectroscopy (C60(CF3)2, C60(CF3)4, and C60(CF3)6), and 2D COSY NMR spectroscopy (C60(CF3)4 and C60(CF3)6). Calculations at the AM1 and DFT levels of theory have led to the prediction of the most likely structures for C60(CF3)2, C1-C60(CF3)4, Cs-C60(CF3)4, and the two most likely structures of C1-C60(CF3)6. 相似文献
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The molecular structure and absorption spectra of monothio- and dithio-naphthalimides were compared to their naphthalimide analogues using AM1, PM3 and ZINDO/S semiempirical quantum chemical methods. The substitution of the 4R-naphthalimide oxygen atoms by sulphur atoms resulted in a red-shift of the absorption spectra by Δλmax60-65 and 100-140 nm, respectively. The thionated naphthalimide derivatives do not show observable fluorescence due to intersystem crossing to the triplet -states localised at the CS groups. The -absorption bands of monothioimides are located at 525-580 nm (ε=60-80) and those for dithioimides at 535-560 nm (ε=140-390) and 628-686 nm (ε=34-68). None of these transitions are solvent sensitive. The -transitions of N-phenylthioimides have also a small contribution from -states due to a partial conjugation between CS group and π-electronic system of the N-phenyl ring. As a result, the bands of aromatic substituted N-phenylthioimides are red-shifted as compared to those of the aliphatic N-methyl-thioimides. 相似文献
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The syntheses of organochalcogen-supported azacalix[3]arenes are described in a one-pot manner in satisfactory yields. A remarkably selective potentiometric response was accomplished for uranyl ions over a variety of other metal ions, including alkali (Na+, K+), alkaline-earth (Mg2+, Ca2+, Ba2+), transition and heavy metal ions (Co2+, Ni2+, Cu2+, Ag+, Fe3+, Zn2+, Cd2+ and Pb2+) using an ion-selective electrode based on compound 3 incorporated into a polymeric (PVC) membrane. 相似文献
15.
Stefania Mele 《Journal of fluorine chemistry》2004,125(2):261-269
The mixtures of sodium and ammonium salts of three homologous perfluoropolyether carboxylic acids having Cl-terminated perfluoroalkyl group (Cl-PFPE) and differing in the average molecular weight (MW) were examined. The surfactants, namely n2, n3 and n4, have two, three and four PFPE units, respectively. Each surfactant was studied alone and in mixture with the other surfactants with the same counterion. NMR chemical shifts were measured for each surfactant and for the mixtures in different concentrations. For a given mixture the micelle composition, Xi, can be determined from the observation of the chemical shifts of the micellar components. It was found that Cl-PFPE surfactant mixtures form in water mixed micelles which contain the surfactants in equilibrium with monomeric species. The analysis of NMR chemical shift variations allowed evaluating the partition of the various surfactants in the mixed aggregates as a function of the total concentration. Composition of mixed micelles resembles ideal mixing predictions particularly at high surfactant concentrations. 相似文献
16.
Y. Lu Y. Morioka T. Matsui T. Tanaka H. Yoshii R. I. Hall K. Ito T. Hayaishi 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,35(2):125-129
The mass spectra of Xe
n
+
clusters (n=2–13) were recorded using a supersonic beam and an ion time-of-flight mass analyser. The yield of Xe
2
+
, Xe
3
+
and Xe
4
+
cluster ions was measured with a resolution of 0.1 Å (1 meV) in the 1024–1113 Å (11.1–12.1 eV) region. Autoionizing Rydberg series of Xe2 converging to theC
23/2u
state of Xe
2
+
were observed in the spectrum of Xe
2
+
. The photoionization yield of Xe
3
+
and Xe
4
+
ions each displayed similar broad features that contained no fine structure corresponding to vibrational states. The broad features were assigned to autoionizing Rydberg series by analogy with the dimer ion spectrum. 相似文献
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J. Hirokawa M. Ichihashi S. Nonose T. Kondow 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,31(3):187-189
Collision of Ar cluster ions, Ar
n
+
(n=3–16), with He and Ne atoms was investigated by use of mass spectroscopic techniques. The cross sections for the production of Ar
n
+
(nn) were measured as functions of the size of the parent cluster ion and the collision energy (0.1–10 eV in the center-of-mass frame). These results were analyzed in the scheme of hard-sphere spectator collision with RRK theory. It was concluded that the reaction proceeds via collisional excitation of the parent cluster ion and following sequential loss of the constituent Ar atoms.This paper was originally submitted in connection with the 2nd. Int. Conference on Atomic and Nuclear Clusters held in Santorini from 28. June-2. July 1993 and is published here as a regular article after an independent refereeing procedure according to the standards of Z. Phys. D 相似文献
20.
K. Kirihara H. Hyodo Z. Wang K. Kawaguchi T. Sasaki K. Soga 《Journal of solid state chemistry》2006,179(9):2799-2804
We measured electrical conductance of single crystalline boron nanobelts having α-tetragonal crystalline structure. The doping experiment of Mg was carried out by vapor diffusion method. The pure boron nanobelt is a p-type semiconductor and its electrical conductivity was estimated to be on the order of 10-3 (Ω cm)−1 at room temperature. The carrier mobility of pure boron nanobelt was measured to be on the order of 10−3 (cm2 Vs−1) at room temperature and has an activation energy of ∼0.19 eV. The Mg-doped boron nanobelts have the same α-tetragonal crystalline structure as the pristine nanobelts. After Mg vapor diffusion, the nanobelts were still semiconductor, while the electrical conductance increased by a factor of 100-500. Transition to metal or superconductor by doping was not observed. 相似文献