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861.
Photochemical Reactions of Cyclopentadienylbis(ethene)rhodium with Phenanthrene, Acenaphthylene, and Triphenylene, and Unusual H Exchange between η2-Coordinated Phenanthrene or Acenaphthylene and η5-Cyclopentadienyl Ligands During UV irradiation of [CpRh(C2H4)2] (Cp = η5-C5H5) in hexane/ether in the presence of phenanthrene one ethene ligand is displaced by coordination of the 9,10 double bond of phenanthrene, and (η5-cyclopentadienyl) (η2-ethene)(η2-9,10-phenanthrene)rhodium ( 1 ) is formed. The analogous reaction in hexane in the presence of acenaphthylene occurs with formation of the complexes (η2-1,2-acenaphthylene)(η5-cyclopentadienyl)(2-ethene)rhodium 2 and bis(η2-1,2-acenaphthylene)(η5-cyclopentadienyl)rhodium 3 in which one and two ethene molecules of [CpRh(C2H4)2], respectively, are substituted by η2-1,2-acenaphthylene. The irradiation of [CpRh(C2H4)2] with triphenylene in hexane yields the compounds [CpRh(η4-1,2,3,4-triphenylene)] ( 4 ), [(CpRh)2(μ-η3: η3-triphenylene)] ( 5 ), and [(CpRh)3(μ3-η2: η2: η2-triphenylene)] ( 6 ). Despite the partially very low yields the new complexes could be unequivocally characterized spectroscopically and in the case of 1 and 3 by X-ray structural analysis. The compounds 1 and 2 in solution reveal a novel dynamic behaviour; via an intramolecular C? H activation, exchange occurs between the protons of the η2-coordinated arene and the Cp ligand. The complex 4 in solution is fluxional, too. 相似文献
862.
In‐Chul Hwang Jung Hee Jang Taek Hyeon Kim Kwang Ha 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(4):o196-o198
The molecule of the title compound, C16H21NO4, is chiral and has three asymmetric centres. The absolute configuration was not determined via diffraction measurements on the crystal, but was established from the known absolute configuration of the starting material. In the crystal structure, the molecules assemble through intermolecular hydrogen bonds into a macrostructure with helical channels. 相似文献
863.
The MP2 and CCSD(T) basis set limit binding energies of various hydrogen-bonded clusters were estimated via basis set extrapolation
employing the correlation consistent aug-cc-pVDZ and modified aug-cc-pVDZ set containing extra polarization functions from
cc-pVTZ set. By adopting the optimal interval for the difference between the cardinal numbers (X) corresponding to two basis sets in the X
−3 type extrapolation scheme the estimated binding energies for (H2O)n and (HF)n (n=3−5) are shown to be close to the reference basis set limit values within the error bounds in many cases, manifesting the
significance of these basis sets in studying the structures and binding of large hydrogen-bonded clusters. 相似文献
864.
Min Su Kim Kwang Gug Yim Soaram Kim Giwoong Nam Jae-Young Leem 《Journal of Sol-Gel Science and Technology》2011,59(2):364-370
Nanocomposites composed of nano-fibrous ZnO thin films and porous silicon (PS) were prepared and examined by atomic force
microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) to investigate their structural
and optical properties. PS, consisting of irregular and random nanosized-pores, was prepared by electrochemical anodization.
The nano-fibrous ZnO thin films were grown on PS by the sol-gel spin-coating method. The texture coefficient (TC
(hkl)) of the nano-fibrous ZnO thin films was calculated to determine the preferred orientation. The nano-fibrous ZnO thin films
were grown with a c-axis preferred orientation. The residual stress in the films was reduced in the case of PS. The observed broad PL emission
peak from 460 to 598 nm was attributed to coupled emission from ZnO to PS. The results show that white light luminescence
with blue, green, and red emission peaks having highly uniform intensities can be obtained from the nanocomposite via a relatively
simple and low-cost sol-gel spin-coating method. 相似文献
865.
Kwang Y. Kim 《Numerical Methods for Partial Differential Equations》2005,21(4):791-809
In this article we construct and analyze a mixed finite volume method for second‐order nonlinear elliptic problems employing H(div; Ω)‐conforming approximations for the vector variable and completely discontinuous approximations for the scalar variable. The main attractive feature of our method is that, although the vector variable is H(div; Ω)‐conforming, one can eliminate it in a local manner to obtain a discontinuous Galerkin method for the scalar variable. Optimal error estimates will be established for both vector and scalar variables. We also present a fully discrete version of this method that is more convenient for computational purposes. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005 相似文献
866.
A condition for the complete destructive interference of partially coherent fields emerging from pinholes in an opaque screen is derived, with the assumption of symmetry in both their geometric positions and coherence properties. We use this condition to theoretically investigate the simultaneous production of phase singularities of the optical field and of the spectral degree of coherence. We find that in cases where the number of point sources is even, a new type of mixed field/correlation singularity is observed. 相似文献
867.
Two proofs of a theta function identity of R.W. Gosper and R. Schroeppel are given. A cubic analogue is presented, and several interesting special cases are noted. 相似文献
868.
Geon Seok Kim Jong Kwan Lee Mi Ju Choi Kwang Hee Lee 《Journal of Polymer Science.Polymer Physics》2008,46(3):223-232
The morphological development and crystallization behavior of a poly(ethylene terephthalate)/poly(hydroxyl ether of bisphenol A) (phenoxy) blend were studied with time‐resolved light scattering, optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering (SAXS). During annealing at 280 °C, liquid–liquid phase separation via spinodal decomposition proceeded in the melt‐extruded specimen. After the formation of a domain structure, the blend slowly underwent phase homogenization by the interchange reactions between the two polymers. Specimens annealed for various times (ts) at 280 °C were subjected to a temperature drop and the effects of liquid‐phase changes on crystallization were then investigated. The shifts in the position of the cold‐crystallization peaks indicated that the crystallization rate is associated with the composition change of the separated phases as well as the change of the sequence distribution in polymer chains during annealing. The morphological parameters at the lamellar level were determined by a correlation function analysis on the SAXS data. The crystal thickness (lc) increased with ts, whereas the amorphous layer thickness (la) showed little dependence on ts. Observation of a constant la value revealed that a large number of noncrystallizable species formed by the interchange reactions between the two polymers were excluded from the lamellar stacks and resided in the interfibrillar regions, interspherulitic regions, or both. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 223–232, 2008 相似文献
869.
870.
Kakarla Raghava Reddy Kwang‐Pill Lee Anantha Iyengar Gopalan Min Seok Kim Ali Md Showkat Young Chang Nho 《Journal of polymer science. Part A, Polymer chemistry》2006,44(10):3355-3364
Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5‐diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe–Pd alloy nanoparticles were embedded into the MWCNT–SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with γ radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of γ radiation. The existence of metallic/alloy particles in the MWCNT–SPAN matrix was further ascertained through characterization by high‐resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe–Pd nanoparticles of various sizes in the MWCNT–SPAN matrices. There were changes in the electronic properties of the MWCNT–SPAN–M composites due to the interaction between the metal nanoparticles and MWCNT–SPAN. Metal‐nanoparticle‐loaded MWCNT–SPAN composites (MWCNT–SPAN–M; M = Fe, Pd, or Fe–Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT–SPAN–M composites was approximately 1.5 S cm?1, which was much higher than that of SPAN (2.46 × 10?4 S cm?1). Metal/alloy‐nanoparticle‐embedded, MWCNT‐based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355–3364, 2006 相似文献