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91.
Mehrdad Pourayoubi Atekeh Tarahhomi Fatemeh Karimi Ahmadabad Karla Fejfarová Arie van der Lee Michal Dušek 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(4):o164-o169
In N,N′‐di‐tert‐butyl‐N′′,N′′‐dimethylphosphoric triamide, C10H26N3OP, (I), and N,N′,N′′,N′′′‐tetra‐tert‐butoxybis(phosphonic diamide), C16H40N4O3P2, (II), the extended structures are mediated by P(O)...(H—N)2 interactions. The asymmetric unit of (I) consists of six independent molecules which aggregate through P(O)...(H—N)2 hydrogen bonds, giving R21(6) loops and forming two independent chains parallel to the a axis. Of the 12 independent tert‐butyl groups, five are disordered over two different positions with occupancies ranging from to . In the structure of (II), the asymmetric unit contains one molecule. P(O)...(H—N)2 hydrogen bonds give S(6) and R22(8) rings, and the molecules form extended chains parallel to the c axis. The structures of (I) and (II), along with similar structures having (N)P(O)(NH)2 and (NH)2P(O)(O)P(O)(NH)2 skeletons extracted from the Cambridge Structural Database, are used to compare hydrogen‐bond patterns in these families of phosphoramidates. The strengths of P(O)[...H—N]x (x = 1, 2 or 3) hydrogen bonds are also analysed, using these compounds and previously reported structures with (N)2P(O)(NH) and P(O)(NH)3 fragments. 相似文献
92.
M.E. Mora-Ramos C.A. Duque E. Kasapoglu H. Sari I. Sökmen 《Journal of luminescence》2012,132(4):901-913
In this work we are studying the intense laser effects on the electron-related linear and nonlinear optical properties in GaAs–Ga1?xAlxAs quantum wells under applied electric and magnetic fields. The calculated quantities include linear optical absorption coefficient and relative change of the refractive index, as well as their corresponding third-order nonlinear corrections. The nonlinear optical rectification and the second and third harmonic generation coefficients are also reported. The DC applied electric field is oriented along the hererostructure growth direction whereas the magnetic field is taken in-plane. The calculations make use of the density matrix formalism to express the different orders of the dielectric susceptibility. Additionally, the model includes the effective mass and parabolic band approximations. The intense laser effects upon the system enter through the Floquet method that modifies the confinement potential associated to the heterostructure. The results correspond to several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation. They suggest that the nonlinear optical absorption and optical rectification are nonmonotone functions of the dimensions of the heterostructure and of the external perturbations considered in this work. 相似文献
93.
The dissociation constants of carminic acid (7-D-glucopyronosyl-3,5,6,8-tetra- hydroxy-1-methyl-9,10-dioxo-anthracene-2-carboxylic acid) (CA), together with the stability constants of its Cu(II), Zn(II), Ni(II), Co(II) and Hg(II) complexes, were studied potentiometrically in aqueous medium at 25.0?(1)?°C, and at the ionic background of 0.1?mol?dm?3 of NaCl, and determined with the SUPERQUAD computer program. It has been observed that carminic acid has five dissociation constants, and for H5L their values are 3.39?(7), 5.78?(7), 8.35?(7), 10.27?(7), and 11.51?(7). This ligand behaves as a bi-dentate ligand, and the carboxyl and the ortho hydroxy groups of the ligand coordinate to the metal ions. Various metal complexes were produced in solution under the experimental conditions, for each metal ion used, including hydrolyzed species. The species distribution curves of the complexes formed in the solution were calculated and reviewed. The stability of the complexes was found to follow the order: Cu(II) > Zn(II) > Ni(II) > Co(II) > Hg(II). 相似文献
94.
Fifth-order nonlinear visible-infrared spectroscopy is used to probe coherent and incoherent vibrational energy relaxation dynamics of highly excited vibrational modes indirectly populated via ultrafast photoinduced back-electron transfer in a trinuclear cyano-bridged mixed-valence complex. The flow of excess energy deposited into four C≡N stretching (ν(CN)) modes of the molecule is monitored by performing an IR pump-probe experiment as a function of the photochemical reaction (τ(vis)). Our results provide experimental evidence that the nuclear motions of the molecule are both coherently and incoherently coupled to the electronic charge transfer process. We observe that intramolecular vibrational relaxation dynamics among the highly excited ν(CN) modes change significantly en route to equilibrium. The experiment also measures a 7 cm(-1) shift in the frequency of a ~57 cm(-1) oscillation reflecting a modulation of the coupling between the probed high-frequency ν(CN) modes for τ(vis) < 500 fs. 相似文献
95.
Naceri Salah. E. Izerrouken M. Sari A. Ryelandt S. Menchi O. Ghamnia M. 《Journal of Radioanalytical and Nuclear Chemistry》2020,323(2):817-824
Journal of Radioanalytical and Nuclear Chemistry - Cold-worked zircaloy-4 was irradiated by 165 keV Ar ion at room temperature. The aim of the study is to understand the correlation... 相似文献
96.
Latin hypercube sampling is often used to estimate the distribution function of a complicated function of many random variables. In so doing, it is typically necessary to choose a permutation matrix which minimizes the correlation among the cells in the hypercube layout. This problem can be formulated as a generalized, multi-dimensional assignment problem. For the two-dimensional case, we provide a polynomial algorithm. For higher dimensions, we offer effective heuristic and bounding procedures.Supported in part by a grant from the National Institute of Standards and Technology (60NANB9D-0974).Supported in part by grants from the Office of Naval Research (N00014-90-J-1324) and the Air Force Office of Scientific Research (F49 620-90-C-0022).Research partially performed while visiting the Department of Mathematics, Brunel University, Uxbridge, England. 相似文献
97.
Ayegül Gk Bekir Sari Muzaffer Talu 《Journal of Polymer Science.Polymer Physics》2004,42(18):3359-3367
This article deals with the chemical synthesis and characterization of poly(2‐fluoroaniline) (P2FAn) and polyfuran (PFu) homopolymers and PFu/P2FAn and P2FAn/PFu composites. P2FAn and PFu homopolymers were synthesized using ammonium persulfate and antimony (III) chloride as catalyst, respectively. These homopolymers and composites were studied in the doped state using Fourier transform infrared spectroscopy and ultraviolet–visible absorption spectroscopy, thermogravimetric analysis, scanning electron microscopy, four‐probe conductivity technique, and Gouy Scale measurements. PFu/P2FAn and P2FAn/PFu composites were found to possess different thermal, conductivity, electronic, and morphological properties from each other when synthesis order of guest and host polymers was varied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3359–3367, 2004 相似文献
98.
M. Aksu S. Durmu M. Sari K. C. Emregül I. Svoboda H. Fuess O. Atakol 《Journal of Thermal Analysis and Calorimetry》2007,90(2):541-547
N,N′-bis(salicylidene)-1,3-propanediamine (LH2), N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH2), N,N′-bis(salicylidene)-2-hydroxy-1,3-propanediamine (LOH3), N,N′-bis(2-hydroxyacetophenylidene)-1,3-propanediamine (LACH2) and N,N′-bis(2-hydroxyacetophenone)-2,2′-dimethyl-1,3-propanediamine (LACDMH2) were synthesized and reduced to their phenol-amine form in alcoholic media using NaBH4 (LHH2, LDMHH2, LOHHH2, LACHH2 and LACDMHH2). Heterodinuclear complexes were synthesized using Ni(II), Zn(II) and Cd(II) salts, according to the template method in DMF
media.
The complex structures were analyzed using elemental analysis, IR spectroscopy, and thermogravimetry. Suitable crystals of
only one complex were obtained and its structure determined using X-ray diffraction, NiLACH·CdBr2·DMF2, space group orthorhombic, Pbca, a=20.249, b=14.881, c=20.565 ? and Z=8. The heterodinuclear complexes were seen to be of [Ni·ligand·MX2·DMF2] structure (ligand=LH2−, LDMH2−, LOHH2−, LACH2−, LACDMH2−, M=ZnII, CdII, X=Br−, I−). Thermogravimetric analysis showed irreversible bond breakage of the coordinatively bonded DMF molecules followed by decomposition
at this temperature. 相似文献
99.
Miloslav Ku
era Eduard Hladký Karla Majerov 《Journal of polymer science. Part A, Polymer chemistry》1967,5(8):1881-1887
The polymerization of dioxolane initiated by the ~Si⊕HSO ion pair is greatly influenced by water which changes the overall polymerization rate. Particularly great changes are brought about at certain higher conversions (whose values are also a function of an initial concentration of water). The polymerization practically stops at these conversions and the system appears to be close to a monomer—polymer equilibrium. It is shown that the equation Voverall = f([H2O]), which describes the dependence of the overall rate of polymerization on the concentration of water and which was originally derived for the polymerization of trioxane, holds also for the polymerization of dioxolane. The decrease of water concentration during the polymerization was measured and the observed equilibrium was shown to be a kinetic phenomenon. 相似文献
100.