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41.
Equilibrium geometries of 16 possible isomers for C74(BN)2 were studied by INDO series of methods, to indicate that the most stable three geometries are those where boron and nitrogen atoms substitute carbon atoms located at the same hexagon near the longest axis of C78 (C2v) to form B-N-B-N unit. Electronic spectra of C74(BN)2 were investigated with INDO/CIS method. The reason for the red shift of UV absorptions for C74(BN)2 compared with those of C78 (C2v) was discussed. IR spectra for 9,8,28,29-C74(BN)2 and 28,29,30,31-C74(BN)2 were calculated on the basis of AM1 geometries. 相似文献
42.
A new anthraquinone glycoside, rubiayannone‐A ( 1 ), and a new coumarin, rubilatin‐A ( 2 ), together with twenty‐two known compounds were isolated and characterized from the roots of Rubia ustulata. A new anthraquinone, 2‐carbomethoxyanthraquinone ( 3 ), and rubiayannone‐A, 2‐formylanthraquinone were obtained from the roots of R. yunnanensis. The structures of those compounds were elucidated by spectroscopic methods. The antiplatelet aggregation activity of the isolated compounds 1, 4~6 were also discussed. 相似文献
43.
IntroductionDAisoneofessentialparticipantsintheneuro transmissionprocessinmammaliancentralnervoussys tem .AlossofDA containingneuronsmayresultinsomeseriousdiseasesuchasParkinsonism .1Sinceitsdiscov eryinthe 195 0s ,DAhasbeenofinteresttoneuroscien tistsandchem… 相似文献
44.
The structure elucidation of a new zinc phosphate [Co(II)(en)(3)][Zn(4)(H(2)PO(4))(3)(HPO(4))(2)(PO(4))(2 H(2)O)(2)] (1) reveals that the racemic cobalt complex templates the zinc phosphate framework in such a way that the local C(2) point symmetry of the structural motif of the inorganic framework conforms with that of the cobalt complex pairing with it, in essence transferring its chirality to the inorganic host. An analysis of hydrogen bonding between the guest molecules and the inorganic host framework reveals that hydrogen bonding is responsible for the stereospecific structural arrangement. Upon examining previously reported chiral metal-complex-templated structures of metal phosphates, it is revealed that such hydrogen bonding is the common origin for inducing chirality transfer in metal-phosphate frameworks templated with chiral metal complexes. Crystal data of 1: orthorhombic, Pbcn (no. 60), a=10.4787(8) A, b=20.0091(14) A, c=14.9594(10) A, and Z=2. 相似文献
45.
Herein, we demonstrate that silica films with perpendicular macroporous channels and accessible ordered mesopores can be conveniently prepared. The hierarchical macroporous–mesoporous silica films are synthesized by using zinc oxide nanorod array as macroporous template and CTAB surfactant as mesoporous template. In basic surfactant-containing solution, ordered mesoporous silica shells homogeneously grow on the zinc oxide nanorod array. The growth of the mesostructures do not require any chemical modification for the zinc oxide nanorod, which opens a new way for preparing hierarchical silica films with perpendicular mesochannels. The prepared hierarchical macroporous–mesoporous silica films possess a uniform thickness of 2 mm, large perpendicular macropores with a length of 1.8 mm and a width of 80 nm, and accessible ordered mesopores. Separation experiment demonstrates that this macroporous–mesoporous film can effectively separate biomolecules with different sizes. 相似文献
46.
Jing?Zhou Yuqi?Liu Liming?Tang Xinchen?Teng Ning?Tang Zhongxian?HuangEmail author 《中国科学B辑(英文版)》2003,46(1):64-74
Two mutants of the zinc finger protein, ZNF191 (243–368) I323W and R327W, are successfully obtained by site-directed mutagenesis.
The fluorescence spectrum is used to study the interaction between these two mutants and the oligonucleotides. The influence
of the mutation on the interaction has been studied using ethidium bromide (EB) as the fluorescence probe. The binding constants
of the I323W-DNA and R327W-DNA have been calculated and the possible binding models have been discussed. 相似文献
47.
Anand VG Venkatraman S Rath H Chandrashekar TK Teng W Ruhlandt-Senge K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(10):2282-2290
Modified octaphyrins with 34pi electrons have been synthesized and characterized following a simple synthetic methodology. An acid-catalyzed alpha,alpha coupling of tetrapyrranes containing furan, thiophene and selenophene rings resulted in the formation of the respective octaphyrins in relatively good yield. Solution studies by (1)H NMR and 2D NMR methods and single crystal Xray structural characterization reveal an almost flat structure with two heterocyclic rings inverted. Specifically, in 14 two selenophene rings (one on each biselenophene unit) are inverted while in 15 two furan rings (one on each bifuran unit) are inverted when the meso substituent are mesityl groups. On changing the mesityl substituent to m-xylyl group as in 19, the location of ring inversion shifts to pyrrole rings (one on each bipyrrole unit) indicating the dependence of structure on the meso substituents. UV/Vis studies, both in freebase and protonated forms reveal typical porphyrinic character and the aromatic nature of the octaphyrins. The Deltadelta values evaluated by (1)H NMR spectroscopy also support their aromatic nature. The protonated forms of octaphyrins bind TFA anion in a 1:2 ratio. The TFA anions are located one above and below the plane of the octaphyrin macrocycle and they are held by weak electrostatic NH-O interactions similar to that observed for protonated rubyrins. However, in the present case, there is an additional non-electrostatic CH-O interaction involving beta-CH of the inverted heterocyclic ring and the carbonyl oxygen of the TFA. Furthermore, inter molecular interactions between the Cbond;H of the meso-mesityl group and the fluorine of CF(3) group of bound TFA leads to the formation of one-dimensional supramolecular arrays with interplanar distance of 13 A between two octaphyrins. 相似文献
48.
A new type of bismaleimide resin (EPBMI), containing epoxy unit and phosphorus in the main chain, was synthesized. The structure of the new resin was confirmed by infrared spectroscopy (IR), 1H NMR and 13C NMR spectroscopies. In addition, the compositions of the new synthesized bismaleimide with two reactants, 4,4′-diaminodiphenylsulfone (DDS) and 4,4′-diaminodiphenylether (DDE), was used to compare its reactivity and thermal properties with conventional bismaleimide (EBMI). Reactivity was measured by differential scanning calorimetry. Thermogravimetric analysis revealed that the polymers, obtained through the reactions between bismaleimides and diamine agents, also demonstrated excellent thermal properties and high char yield. 相似文献
49.
The Bu(3)Sn radical-induced reaction of o-iodobenzylvinylsilanes and o-iodoallylsilanes leads to cyclic products in yields of 40-60%. These regioselective cyclizations occur with high preference for a 5-exo and a 7-endo mode with a 6-exo mode being absent. An example for ring closure via a 7-exo mode is described. 相似文献
50.
Chin-Pao Cheng Yi Kuo Chuan-Pu Chou Chun-Hu Cheng Tun Ping Teng 《Applied Physics A: Materials Science & Processing》2014,116(4):1553-1559
In this paper, we studied the effect of micro-size WO3 precipitates on the electrochromic characteristics based on aging test. The electrochromic mechanism can be effectively investigated by a solid-state TaN/WO3/ITO capacitor. The experimental results reveal that WO3 electrochromic devices with optimized aging time of 4 days exhibit a higher optical contrast and longer retention time, which is mainly attributed to the formation of micro-size WO3 precipitates during aging process. The performance improvement using micro-size WO3 precipitates has the potential in future large-area window or energy efficient display applications. 相似文献