共查询到20条相似文献,搜索用时 31 毫秒
1.
Novel thiono and seleno phosphoramidate compounds with the general formula (X)(Y)P(C 6H 5) 2; (X = NMe 2 & Y = S, 1a; X = NEt 2 & Y = S, 2a; X = NMe(CH 2Ph) & Y = S, 3a; X = NH(CH 2Ph) & Y = S, 4a; X = NEt(CH 2Ph) & Y = S, 5a; X = N(C(Me) 3) (CH 2Ph) & Y = S, 6a; X = N(CH 2Ph) 2 & Y = S, 7a; X = NMe 2 & Y = Se, 1b; X = NEt 2 & Y = Se, 2b; X = NMe(CH 2Ph) & Y = Se, 3b; X = NH (CH 2Ph) & Y = Se, 4b; X = NEt(CH 2Ph) & Y = Se, 5b; X = N(C(Me) 3)(CH 2Ph) & Y = Se, 6b and X = N(CH 2Ph) 2 & Y = Se, 7b) were prepared and characterized by 1H, 31P and 13C NMR and IR spectroscopy and elemental analysis. 31P chemical shift of thiono and seleno derivatives didn’t show significant different because of their little difference in
electronegativity sulfur and selenium. Hydrophobic parameter of compounds was determined by measurement of octanol-water partition
coefficient by shake-flask technique. Determination of human erythrocyte acetylcholinesterase (hAChE) activity was carried
out according to the Ellman’s modified kinetic method. IC 50 values of the selected thiono and seleno compounds varied from 3.4 to 0.11 and 9.9 to 5.1 mM, respectively. The seleno compounds
show lower affinities for hAChE relative to the thino compounds. These results demonstrate that hydrophobic and electronic
factors of the organophosphorus compounds play a key role on the inhibitory potency. 相似文献
2.
Abstract o ?, m ? and p ? aminobenzoic acid hydrazide (ABAH) complexes with (NH 4) 2 Fe (So 4) 2 and Fe Cl 3 were prepared with the type [ML 2.2H 2O] X. where X = Cl 3 or SO 4. The prepared complexes were investigated using IR, electronic and Mossbauer spectroscopes. The obtained results indicated that the iron ions are present in octahedrally coordinated Fe 2+, and Fe 3+ states. Also the results reveal that all the complexes contain keto form, except m ? ABAH Fe (II) complex which contains enol form in addition to the keto form. 相似文献
3.
We studied the changes in the electronic structure of SrTi 1-xRu xO 3 across the metal-insulator transition. The parent compound, SrTiO 3, is a well known diamagnetic insulator; whereas the doped compound, SrTi 1-xRu xO 3, becomes a ferromagnetic metal above x
C
= 0.35. The techniques used in the study were photoemission (PES) and O 1
s X-ray absorption (XAS) spectroscopy. The experimental spectra were analyzed in terms of band structure and Hubbard model
calculations. The PES and XAS spectra of SrTi 1-xRu xO 3 show the Ru 4
d bands growing in the band gap of SrTiO 3 . The analysis in terms of the Hubbard model indicates that the Ti 3
d and Ru 4
d bands are mostly decoupled. This suggests that the metal-insulator transition is a percolation transition like that of metals
embedded in a rare gas matrix. Electron correlation effects are present in this system, but they do not seem to play a major
role in the transition.
Received 10 September 2001 相似文献
4.
ABSTRACTAb initio MP2/aug’-cc-pVTZ calculations have been performed on pnicogen-bonded complexes with CO and CS as electron-pair donors to PH 2X, for X?=?F, NC, OH, CN, CCH, and H. CO:PH 2X and OC:PH 2X complexes are stabilised by traditional pnicogen bonds. CS is an electron-pair donor through its in-plane π system to four PH 2X molecules. It forms C ···?P phosphorus-shared bonds with some ion-pair character with PH 2F, PH 2(OH-Z), and PH 2(OH-E), and traditional pnicogen bonds with all PH 2X except PH 2F. C-O and C-S stretching frequencies are blue-shifted for C ···P pnicogen bonds, and red-shifted for O ···P and S ···P bonds. EOM-CCSD spin-spin coupling constants 1pJ(P-C) for OC:PH 2X and 1pJ(P-O) for CO:PH 2X are characteristic of complexes stabilised by traditional pnicogen bonds. Coupling constants 1pJ(P-C) as a function of the P-C distance for SC:PH 2X illustrate the evolution of the C ···P pnicogen bond. They increase as the P-C distance decreases in complexes with traditional bonds, reach a maximum for SC:PH 2OH transition structures as the P-C distance further decreases and the bonds gain phosphorus-shared character, and then change sign and continue to decrease as the P-C distance further decreases and the phosphorus-shared pnicogen bonds gain ion-pair character. They approach the values of 1J(P-C) for the cation (H 2PCS) +. 相似文献
5.
We have analyzed the electronic structure and superconducting properties of layered crystals based on BEDT-TTF salts (hereafter
denoted as ET), in which intramolecular interaction among electrons is important. For the case of realistic κ-packing of ET-molecules in a plane of ET 2 dimers we have calculated the electron density of states. Using the calculated electronic structure, we have analyzed the
symmetry of the anisotropic superconducting pairing. The critical value of the effective attraction between electrons for
formation of a bound pair in an empty lattice has been estimated. The relation between the nodes of the d-type order parameter on the anisotropic Fermi surface and superconducting properties of the condensate is discussed in the
Bardeen-Cooper-Schrieffer (BCS) model. The results are in agreement with the known band parameters of the normal phase and
measurements of the magnetic field penetration depth, heat capacity as a function of temperature in the low-temperature range,
and NMR in κ-ET 2X superconducting salts.
Zh. éksp. Teor. Fiz. 113, 715–733 (February 1998) 相似文献
6.
The five isolated-pentagon-rule (IPR) satisfying isomers of C 78, labeled 1-5, or according to symmetry as D 3, C 2v, C'
2v
, D 3h, and D'
3h
, are computed. The cage geometries are optimized at the ab initio HF level with the standard 3-21G basis set (HF/3-21G). The separation energetics is then computed using the B3LYP density-functional
treatment in the standard 6-31G* basis set (B3LYP/6-31G*//HF/3-21G). Harmonic vibrational frequencies are calculated by the
SAM1 semiempirical method. The computed energies, structural and vibrational data are employed in the construction of isomeric
partition functions and evaluation of the relative Gibbs free energies. The results are converted into relative concentrations
for a wide temperature interval. The C'
2v
structure is the most populated throughout while the D 3h species is negligible at all temperatures. The agreement between theory and experiment is reasonable, though some aspects
are still to be clarified.
Received 28 November 2000 相似文献
7.
Single crystals of U(Ni 1-xPd x) 2Si 2 with x = 0.05, 0.09 and 0.135 have been grown. Magnetization and electrical resistivity measurements were performed in a wide range
of temperatures and magnetic fields in order to study stability of magnetic phases in the solid solutions between UNi 2Si 2 and UPd 2Si 2 with a special emphasis on the type of ground state. In UPd 2Si 2 the simple AFI-type antiferromagnetic structure of U moments is observed at low temperatures. UNi 2Si 2 adopts the uncompensated AF structure (UAF) with the + + - stacking of U moments along the c-axis and consequently this compound exhibits a spontaneous magnetization corresponding to 1/3 of the U moment. The substitution
of Pd for Ni leads to a rapid decay of the spontaneous magnetization. The evolution of magnetization and electrical resistivity
behavior with Pd doping is tentatively attributed to the coexistence of the AF-I and UAF phases in the ground state of U(Ni 0.91Pd 0.09) 2Si 2 and U(Ni 0.865Pd 0.135) 2Si 2. In this scenario, the volume fraction of the AF-I phase rapidly grows with Pd doping on account of the UAF. At lowest temperatures
an irreversible transition to the UAF phase is observed when a sufficiently high magnetic field is applied along the c-axis.
Received 28 March 2002 / Received in final form 8 August 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: sech@mag.mff.cuni.cz 相似文献
8.
We have investigated the quantum J
1
-
J
2
-
J
3
model on the honeycomb lattice with exact diagonalizations and linear spin-wave calculations for selected values of J
2
/
J
1
, J
3
/
J
1
and antiferromagnetic ( J
1
> 0) or ferromagnetic ( J
1
< 0) nearest neighbor interactions. We found a variety of quantum effects: “order by disorder" selection of a Néel ordered ground-state,
good candidates for non-classical ground-states with dimer long range order or spin-liquid like. The purely antiferromagnetic
Heisenberg model is confirmed to be Néel ordered. Comparing these results with those observed on the square and triangular
lattices, we enumerate some conjectures on the nature of the quantum phases in the isotropic models.
Received 17 November 2000 and Received in final form 21 January 2001 相似文献
9.
Abstract Laser-induced fluorescence excitation spectra of the methoxy radical have been obtained under sufficiently high resolution in a supersonic jet expansion. The rotational structure associated with its origin band has been identified in the midst of strong overlapping rotational transitions due to the hydroxyl radical in the 31490–31700 cm ?1 spectral region. Rotationally-resolved A 2A 1 - X 2E spectra of the 0 0 0 band of methoxy have been explicitly assigned using the nomenclature for prolate symmetric top transitions in doublet states. 相似文献
11.
Abstract Fourier transform infrared (4000-200 cm 1) and Raman (3500-50 cm ?1) spectra are reported for metal(II) halide 3,5-lutidine (3,5-dimethylpyridine) complexes of the following stoichiometries: M(3,5L) 4X 2 M=Co or Ni, X=C1 or Br; M=Mn or Cu, X=Br; M=Cd, X=I; M(3,5L) 3X 2 M=Fe, X=C1; M=Cu, X=Br; Hg(3,5L) X 2 X=C1 or Br. Vibrational assignments are given for all the observed bands. Some structure- spectra correlations are found. For a given series of isomorphous complexes the sum of the difference between the liquid and ligand values of the vibrational modes of 3,5-lutidine is found to increase in the order of the second ionization potentials of the metals. The frequency shifts are also found to depend on the halogen. 相似文献
12.
We propose a Ginzburg-Landau phenomenological model for the dependence of the critical temperature on microscopic strain in
tetragonal high- T
c
cuprates. Such a model is in agreement with the experimental results for LSCO under epitaxial strain, as well as with the
hydrostatic pressure dependence of T
c
in most cuprates. In particular, a nonmonotonic dependence of T
c
on hydrostatic pressure, as well as on in-plane or apical microstrain, is derived. From a microscopic point of view, such
results can be understood as due to the proximity to an electronic topological transition (ETT). In the case of LSCO, we argue
that such an ETT can be driven by a strain-induced modification of the band structure, at constant hole content, at variance
with a doping-induced ETT, as is usually assumed.
Received 1st October 2001 and Received in final form 5 December 2001 相似文献
13.
By using the published accurate new virial coefficients B 11~B 14 for the hard disk fluids [C. Zhang and B.M. Pettitt, Mol. Phys., 2014, 112, 1427], we here propose a new updated version of Tian-Gui-Mulero equation of state [J.X. Tian, Y.X. Gui and A. Mulero, Phys. Chem. Chem. Phys ., 2010, 12, 13597]. Compared with other proposals, the new version stands strongly to be the only which can reproduce the known virial coefficients B 2~B 13 at the same time that can describe the relation of the compressibility factor versus the packing fraction for the hard disk fluids with high accuracy. 相似文献
14.
ABSTRACTHydrogen storage reactions on Ni ? C 59X(X = B, N) heterofullerene are investigated by using the state-of-the-art density functional theory calculations. The Ni atom prefers to bind at the bridge site between two hexagonal rings, and can bind up to five hydrogen molecules with average adsorption energies of (?0.94, ?0.48, ?0.33, ?0.25 and ?0.20 eV) per hydrogen molecule for Ni ? C 59B, while (?1.20, ?0.60, ?0.41, ?0.28 and ?0.23 eV) per hydrogen molecule for Ni ? C 59N. With no metal clustering, the system gravimetric capacities are expected to be as large as 10.87 and 10.85 wt % for 5H 2NiC 59B?and 5H 2NiC 59N, respectively. While the desorption activation barriers of the complexes 1H 2 + C 59X?(X = B, N)?are outside the Department of Energy domain (?0.2 to ?0.6 eV), the desorption activation barriers of the complexes nH 2 + C 59X(X = B, N)( n = 2 ? 5) are inside this domain. The hydrogen storage of the irreversible 1H 2 + NiC 59X?(X = B, N) and reversible 2H 2 + NiC 59X?(X = B, N) interactions is characterised in terms of density of states and projected densities of states, pairwise and non-pairwise additivity, infrared, Raman, electrophilicity and molecular electrostatic potentials. 相似文献
15.
ABSTRACTThe complexes of H 2X (X?=?O, S, Se) with hypervalent halogens YF 3 and YF 5 (Y?=?Cl, Br, I) have been studied. The σ-hole on the Y atom participates in a halogen bond with the lone pair on the chalcogen atom. In addition, some secondary interactions coexist with the halogen bond in most complexes. The interaction energy correlates with the nature of both X and Y atoms. In most cases, the complex is more stable for the heavier Y atom and the lighter X atom. Of course, there are some exceptions in H 2X···YF 3. YF 3 forms a more stable complex with H 2X than does YF 5. These complexes are dominated by electrostatic interaction and the halogen bond involving H 2S and H 2Se exhibits some covalent character.Halogen bond plays an important role in chemical reactions and multivalent halogens can regulate chemical reactions by participating in a halogen bond. Thus we compare the effect of the chalcogen electron donor on the strength and nature of halogen bonding involving multivalent halogens. 相似文献
16.
We have studied structural and magnetic properties in
small iron oxide clusters,
Fe nO m ( n = 1-5), by means of the
first-principles calculation based on the density functional
theory. We have used not only the usual spin polarized scheme,
but also the scheme for noncollinear magnetism to carry out
efficient optimization in magnetic structure. The result of
FeO m ( m
= 1-4) is in good agreement
with the previous work. We found the stable adduct clusters in
FeO 5 and FeO 6. The
bridge site of oxygen atom is more favorable in energy than any
other site for the clusters of Fe nO
( n
=
2-5). As increasing the number of oxygen atoms, the
alignment of Fe magnetic moments changes from ferromagnetic
configuration to antiferromagnetic one at
Fe nO n ( n
=
2-4). Received 10 September 2002 Published online 3 July
2003 相似文献
17.
The fine-structure and g tensors of the luminescent triplet state of the molybdate anion in single-crystals of CaWO 4:MoO 4, CdMoO 4 and PbMoO 4, all with the scheelite structure, are reported. In all three hosts the MoO24- ion is distorted on excitation. The directions of the principal axes of the fine-structure and g tensors support the idea that the effect results from the combined action of a Jahn-Teller instability and the crystal field. The hyperfine coupling of the 95Mo and 97Mo nuclei points towards excitation to an orbital with a large contribution of Mo 4d 3z2-2r. 相似文献
18.
Deficiency effects in the A site upon the structural, magnetic and electrical properties in the lacunar perovskite manganite
oxides Pr 0.7Sr 0.3-x
xMnO 3 ( 0 ?
x
? 0.3) and Pr 0.7-x
xSr 0.3MnO 3 ( 0 ?
x
? 0.23) have been investigated. This study focuses on the different parameters which govern the magnetic and electrical properties
in such samples. The powder X-ray diffraction patterns for all samples could be indexed either with a rhombohedral perovskite
structure and R
c space group for x
? 0.2 in strontium deficient samples and for x
? 0.1 for praseodymium deficient ones. For other values of x the samples could be indexed in the orthorhombic structure with Pbnm space group. Magnetic and electrical investigations
show that praseodymium and strontium vacancies do not have similar effects on the lacunar compounds. Magnetization measurements
versus temperature show that all our samples exhibit a magnetic transition when the temperature decreases. All the praseodymium
deficient samples exhibit a paramagnetic-ferromagnetic transition when the temperature decreases while the strontium deficient
ones exhibit this transition only for low x values. The magnetic transition temperature shifts to lower values as the strontium deficiency increases (from 265 K for
x
= 0 to 90 K for x
= 0.3) and to higher values with the praseodymium deficiency increase (from 265 K for x
= 0 to 315 for x
= 0.23). Resistivity measurements as a function of temperature show a semiconducting-metallic transition for all x values in the praseodymium lacunar samples and only for low x values ( 0 ?
x
? 0.1) in the strontium lacunar ones when the temperature decreases.
Received 12 April 2000 and Received in final form 8 January 2001 相似文献
19.
Using a new experimental setup we have measured UV ( h
ν = 6.4 eV) photoelectron spectra of cold silicon cluster anions Si
n
-
in a very broad size range. For sizes up to n
= 46 the spectra exhibit rich structures. For larger sizes only smooth spectra have been obtained. No trace of a bandgap has been
found even for clusters with more than 1000 atoms.
Received 30 November 2000 相似文献
20.
In an effort to discover potential cytotoxic agents, a series of novel (Z)-5-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-3-((1-substituted phenyl-1H-1,2,3-triazol-4-yl)methyl)thiazolidine-2,4-dione derivatives (8a–n) were designed and synthesized in various steps with acceptable reaction procedures with quantitative yields and characterized by 1H NMR, 13C NMR, IR, HRMS and ESI–MS spectra. These newly synthesized novel derivatives were screened for their in vitro cell viability/cytotoxic studies against human breast cancer cell line (MCF-7) with various concentrations of 0.625 µM, 1.25 µM, 2.5 µM, 5 µM and 10 µM, respectively. The biological interpretation assay outcome was demonstrated in terms of cell viability percentage reduction and IC50 values against standard reference drug cisplatin. Based on these results, most of the derivatives exhibited promising cytotoxic activity. Among them, particularly compounds 8j (R1?=?OMe and R3?=?NO2) and 8e (R3?=?CF3) demonstrate remarkable cytotoxic activity with IC50 values 0.426 µM?±?0.455 and 0.608 µM?±?0.408, which are even better than the standard drug cisplatin 0.636 µM?±?0.458 and compounds 8m (R2?=?OMe and R3?=?OMe) and 8c (R3?=?OMe) exhibited closely equivalent IC50 values to the standard drug with IC50 values 0.95 µM?±?0.32 and 0.976 µM?±?0.313 and rest of the compounds exhibits moderate cytotoxic activity. Moreover, molecular modeling studies and ADME calculations of the novel synthesized derivatives are in adequate consent with the pharmacological screening results. 相似文献
|