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981.
Zun‐Ting Zhang Yan‐Chang Wang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):o51-o53
In the lattice of the title compound (systematic name: 5,6,7‐trihydroxy‐4′‐methoxyisoflavone monohydrate), C16H12O6·H2O, the isoflavone molecules are linked into chains through R43(17) motifs composed via O—H⋯O and C—H⋯O hydrogen bonds. Centrosymmetric R42(14) motifs assemble the chains into sheets. Hydrogen‐bonding and aromatic π–π stacking interactions lead to the formation of a three‐dimensional network structure. 相似文献
982.
The enthalpies of mixing of glycine, l-α-alanine, l-γ-aminobutyric acid, l-α-valine, l-α-serine and l-α-threonine with cyclohexanone in aqueous solutions and their respective enthalpies of dilution have been measured by calorimetry at 298.15 K. Experimental enthalpies of dilution and mixing have been correlated with the virial expansion equation that was obtained with the McMillan-Mayer theory. The enthalpic interaction parameters hxy, hxxy and hxyy of the amino acids studied with cyclohexanone in aqueous solutions have been evaluated, and the heterotactic enthalpic pair interaction coefficients (hxy) are discussed in terms of solute-solute interactions. 相似文献
983.
An approach was reported to synthesize silica hybridized ruthenium bipyridyl complex through amidation reaction by covalent attachment of bis(bipyridyl)-4,4'-dicarboxy-2,2'-bipyridyl-ruthenium to (3-aminopropyl)-triethoxysilane. The hybrid complex then was gelatinized through acid catalytic hydrolysis method and a sol-gel modified indium tin oxide electrode was prepared via spin coating technique. As prepared indium tin oxide electrode possesses good stability therein with excellent electrochemiluminescence behavior. 相似文献
984.
Self-assembling DNA tiling lattices represent a versatile system for nanoscale construction. Self-assembled DNA arrays provide an excellent template for spatially positioning other molecules with increased relative precision and programmability. Here we report an experiment using a linear array of DNA triple crossover tiles to controllably template the self-assembly of single-layer or double-layer linear arrays of streptavidin molecules and streptavidin-conjugated nanogold particles through biotin-streptavidin interaction. The organization of streptavidin and its conjugated gold nanoparticles into periodic arrays was visualized by atomic force microscopy and scanning electron microscopy. 相似文献
985.
Ewig CS Berry R Dinur U Hill JR Hwang MJ Li H Liang C Maple J Peng Z Stockfisch TP Thacher TS Yan L Ni X Hagler AT 《Journal of computational chemistry》2001,22(15):1782-1800
A class II valence force field covering a broad range of organic molecules has been derived employing ab initio quantum mechanical "observables." The procedure includes selecting representative molecules and molecular structures, and systematically sampling their energy surfaces as described by energies and energy first and second derivatives with respect to molecular deformations. In this article the procedure for fitting the force field parameters to these energies and energy derivatives is briefly reviewed. The application of the methodology to the derivation of a class II quantum mechanical force field (QMFF) for 32 organic functional groups is then described. A training set of 400 molecules spanning the 32 functional groups was used to parameterize the force field. The molecular families comprising the functional groups and, within each family, the torsional angles used to sample different conformers, are described. The number of stationary points (equilibria and transition states) for these molecules is given for each functional group. This set contains 1324 stationary structures, with 718 minimum energy structures and 606 transition states. The quality of the fit to the quantum data is gauged based on the deviations between the ab initio and force field energies and energy derivatives. The accuracy with which the QMFF reproduces the ab initio molecular bond lengths, bond angles, torsional angles, vibrational frequencies, and conformational energies is then given for each functional group. Consistently good accuracy is found for these computed properties for the various types of molecules. This demonstrates that the methodology is broadly applicable for the derivation of force field parameters across widely differing types of molecular structures. Copyright 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1782-1800, 2001 相似文献
986.
987.
The preparation, X-ray crystal structure, and magnetic properties of alternating 1,1- and 1,3-azido-bridged copper(II) complex [Cu(4,4'-dmbpy)(N3)2]n (1, 4,4'-dmbpy = 4,4'-dimethylbipyridine) have been reported. It crystallizes in triclinic system, space group P1, a = 7.9903(1) A, b = 9.3545(9) A, c = 10.754(2) A, alpha = 113.485(1) degrees, beta = 101.399(1) degrees, gamma = 101.897(1) degrees, Z = 2. The magnetic properties of 1 have been investigated in the temperature range 1.5-300 K. Alternating antiferromagnetic (-J = 191.0 cm(-1)) interaction through a 1,3-N3- bridge and ferromagnetic (J = 297.1 cm(-1)) interaction through a 1,1-N3- bridge are obtained for 1 by analyzing the magnetic susceptibility data with the Hamiltonian H = -Jsigma(S2iS2i-1--alphaS2iS2i+1). It's derivatives ([Mn(4,4'-dmbpy)(N3)2]n (2), [Ni(4,4'-dmbpy)(N3)2]n (3), and [Fe(4,4'-dmbpy)(N3)2]n (4) and the heterometallic derivatives [NiMn(4,4'-dmbpy)2(N3)4]n (5) and [CuMn(4,4'-dmbpy)2(N3)4]n (6) have also been synthesized and characterized by electronic and IR spectra. The X-ray powder diffraction and the magnetic properties of 6 have also been discussed. 相似文献
988.
IntroductionItiswellknownthatmetallocenesactivatedwithmethylaluminoxane (MAO)arehighlyactivehomogeneousZiegler Nattacatalyststhatproducepolyolefinwithcon trolledstereoregularityandnarrowmolecularweightdistri bution ,1 4 however,themolecularweightofthepolym… 相似文献
989.
Charge-discharge Behavior of Surface-coated LiMn2O3.95F0.05 Cathode Materials at High Temperature 总被引:1,自引:0,他引:1
ZhaoYongCHEN YanRongLI ZuoLongYU 《中国化学快报》2003,14(12):1296-1298
With inorganic salts such as LiNO3, Li2CO3, surface-coated LiMn2O3.95F0.05 were prepared by melt-impregnation method. When these surface-coated LiMn2O3.95F0.05 were used as cathode materials, their charge-discharge characters were carefully compared. As a result, they exhibited good charge-discharge properties at 50℃ high temperature. Especially, LiNO3 surface-coated LiMn2O3.9F50.05 retained nearly 80% initial reversible capacity after 130 cycles at 50℃. 相似文献
990.
人参挥发油的提取和分析 总被引:7,自引:0,他引:7
应用GC-MS-DS联机分析人参挥发油是当前较好的方法,但人参挥发油的提取方法和GC-MS条件的选择明显影响人参挥发油这一复杂天然混合物的分离和鉴定。本工作严格控制提取条件,提高了挥发油收率,达0.95%;选择最佳GC-MS条件,鉴定出76种化合物,该法稳定重现性好。 相似文献