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排序方式: 共有297条查询结果,搜索用时 9 毫秒
101.
Novel optically active hypervalent iodine(V) reagents with planar chiral crown ether backbones were synthesized using the intramolecular Huisgen reaction as a key step and l-methyl lactate as the source of chirality. The relative configurations of these reagents and stabilities of planar chiralities were determined by DFT calculations. These planar chiral reagents were applied to the hydroxylative dearomatization/[4 + 2]-dimerization reactions of phenols to afford bisthymol and biscarvacrol, a natural product, with moderate enantioselectivities. 相似文献
102.
Louis H. A. Prins Armand de Vries Mino R. Caira Douglas W. Oliver Sandra van Dyk Sarel F. Malan 《Journal of chemical crystallography》2008,38(9):705-709
Abstract Polycyclic hydrocarbon compounds exhibit a wide variety of biological activities, ranging from antiviral to Parkinson’s disease.
Several structures such as the adamantanes have reached clinical status and are used therapeutically to treat, amongst others,
neurodegenerative disorders such as Alzheimer’s. Polycyclics have also been utilised as carrier molecules to facilitate entry
of drugs into the brain. The synthesis, molecular and crystal structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.02,10.03,14.04,9.09,13.012,15]tetradecane, are reported. NMR spectroscopy was applied for structure elucidation of the novel compound and a rearrangement
mechanism is proposed for its formation. This compound crystallises in the orthorhombic system, space group Pbca (no. 61). The unit cell parameters are: a = 12.3763 (7), b = 11.6597 (6), c = 15.0539 (8) ?,
V = 2172.3 (2) ?3
, and Z = 8 molecules in the unit cell. The reported structure was confirmed by X-ray analysis, which showed that the title molecules
associate into centrosymmetric dimers via N–H···O hydrogen bonding.
Index Abstract The synthesis and structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.02,10.03,14.04,9.09,13.012,15]tetradecane, are reported in this article.
相似文献
103.
Tsunashima R Matsumoto T Hoshino N Niiho W Kimura M Kondo K Suyama Y Nishioka Y Kawamata J Noro S Nakamura T Akutagawa T Ishiguro K 《Dalton transactions (Cambridge, England : 2003)》2012,41(33):10060-10064
A new salt-[Ni(II)(DMSO)(5)(TTFPy)](2)[α-SiW(12)O(40)] (1)-based on polyoxometalates was prepared by coordinating a cationic electron donor of pyridyltetrathiafulvalene (TTFPy) with Ni(II). Although the TTFPy molecule did not form a salt with the anionic α-[SiW(VI)(12)O(40)](4-) because of the weak charge-transfer (CT) interaction, the coordination of Ni with the pyridyl moiety permitted salt formation driven by electrostatic interaction, giving a single crystal of 1. Crystallographic analysis, UV-vis and IR spectroscopy and electrochemical characterization revealed that the fully oxidized α-[SiW(VI)(12)O(40)](4-) was crystallized with the neutral TTFPy moiety from the acetonitrile solution because of the low electron-withdrawing ability of α-[SiW(VI)(12)O(40)](4-), forming a brown-orange crystal. The crystal colour quickly turned to black by immersing in methanol, due to CT from TTF moiety to α-[SiW(VI)(12)O(40)](4-), which was caused by the solvent effect. Increase in the solvent acceptor number from 18.9 for acetonitrile to 41.3 for methanol resulted in the enhancement of the electron withdrawing ability of α-[SiW(VI)(12)O(40)](4-) by 0.317 V in methanol. 相似文献
104.
Mino Yang 《Journal of Molecular Spectroscopy》2006,239(1):108-114
Intensity pattern of the vibronic transitions of a molecular dimer consisting of two molecules interacting through the Coulombic coupling is theoretically studied using a reduced density-matrix approach. The monomeric molecules are assumed to be electronic two-state systems. A single vibration mode with a high frequency and a continuous distribution of low-frequency phonons represented by the Ohmic spectral density are coupled to the electronic transition of the respective molecules. The spin-Boson model is employed to include the effect of electron-vibration and electron-phonon couplings. The intermolecular Coulombic coupling is assumed to be weak (inducing the Förster type of energy transfer process). It is found that, in addition to the well-known excitonic shifts, the intensity of the vibronic side bands reduces with the intermolecular coupling strength in the J-aggregate type of dimer while it increases in the H-aggregate type. When the vibronic bands are blurred by the broadening resulting from the coupling of the electrons to the continuous distribution of the phonons, the absorption line shape shows a wide range of variation depending on the strength of the intermolecular coupling. 相似文献
105.
106.
E. M. Yeatman Mino Green E. J. C. Dawnay M. A. Fardad F. Horowitz 《Journal of Sol-Gel Science and Technology》1994,2(1-3):711-715
This paper describes progress towards a silica-on-silicon integrated optics technology based on sol-gel. In particular, the aim of this work is to use porous sol-gel films as a host for semiconductor microcrystallites, in order to achieve optical Kerr effect devices. Control of crystallite size is important to maximize the nonlinear effect, and also has a strong influence on band-gap, and thus the wavelength of operation. We are examining the control of pore size distribution, via sol-gel process parameters, as a means of setting crystallite size, and for this reason have developed a technique for the measurement of micropore distributions in films. Results of this technique are presented; these give the first detailed measurements of pores below 10 Å in diameter. The fabrication and measurement of initial doped films is described, giving strong evidence for quantum confinement. 相似文献
107.
Yoshiharu Ishikawa Norihisa Kato Shigeyuki Suematsu Tokihiro Kuroyanagi 《Nuclear Physics A》1982,380(3)
In the experiments on 74Ge(d, pγ)75Ge, a 52.5±0.1 keV γ-ray was found in 75Ge with a half-life of 216±5 ns. From the analysis of the γ-ray spectra the conversion coefficient of the 52.5 keV γ-ray was determined. Then, a new level of
is confirmed to exist at 192.5 keV. The reduced transition probabilities of the 52.5 keV transition are deduced to be (6.9+5.6 −2.1) × 10−5 for B(M1) and 31+3 −2 for B(E2) in Weisskopf units. 相似文献
108.
Poly[lithium methacrylate-co-oligo(oxyethylene)methacrylate] film was prepared as a polymeric solid electrolyte which showed lithium ionic conductivity of 2×10?7(S/cm). This film contained no organic plasticizer nor low molecular weight lithium salts and shown to be a single-ion conductor in solid state. Li+ ionic conductivity was deeply influenced by the glass transition temperature and lithium methacrylate content of this film. A rechargeable battery composed of metallic lithium/this film/graphite showed better characteristics than any previously reported systems using polymeric solid electrolytes. 相似文献
109.
Mino R. Caira Luigi R. Nassimbeni Janet L. Scott Fumio Toda 《Journal of chemical crystallography》1994,24(8):495-501
The crystal structures and thermal analyses of the host compound, N,N,N,N-tetraisopropylfumaride, witho-cresol,m-cresol and water are reported and compared to that of thep-cresol complex previously reported in an attempt to elucidate the reasons for host selectivity. 相似文献
110.
N,N-Diisopropylcarbamoylisatin showed polymorphism and was crystallized into two different space groups, chiral P212121 and racemic P21/c from the solvent; the polymorphism could be controlled by crystallization from the melt using the difference of melting points. 相似文献