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861.
Time-dependent density-functional theory(TDDFT)has been applied to calculate the electronic structure and second-order nonlinear optical(NLO) properties of some organic molecules.The two-dimensional(2-D)charge transfer charateristics of calculated molecules were studied and compared with corresponding experimental results.All the theoretical results agree well with the measurement.For 2-D molecule with two-fold symmetry,the dominant charge transfer is off-diagonal,while for three-fold symmetry 2-D molecule,the dominant charge transfer is not only between branches and central group but also among branches. 相似文献
862.
Jin‐Yu Sun Zhen Zhao Yong‐Chao Ma Miao‐Li Zhu Xiang‐Dong Zhang 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(1):m4-m6
The crystal structure of the title compound, μ‐2‐hydroxybutanedioato‐1κ2O4,O4′:2κ3O1,O2,O4‐nitrato‐2κO‐tris(1,10‐phenanthroline)‐1κ4N,N′;2κ2N,N′‐dicopper(II) nitrate tetrahydrate, [Cu2(C4H3O5)(NO3)(C12H8N2)3](NO3)·4H2O, contains an unsymmetrical dinuclear copper complex with Cu(phen)2 and Cu(phen)(NO3) moieties (phen is 1,10‐phenanthroline) bridged by a malate (2‐hydroxybutanedioate) ligand, which acts as a double‐bridging and tetradentate ligand. As a result of this double‐bridging action, especially the direct coordination of the O atom of one carboxylate group of malate to the two Cu atoms, the Cu⋯Cu distance is only 4.199 (1) Å and the two phen planes are roughly parallel [the shortest interplanar distance is 3.28 (1) Å], exhibiting an obvious intramolecular π–π stacking interaction. 相似文献
863.
Deshui Ruan Weiping Li Luofu He Qizhu Hu 《Journal of Thermal Analysis and Calorimetry》1995,45(1-2):235-242
The phase diagrams of four binary systems (C10H21NH3)2CoCl4?(C16H33NH3)2CoCl4, (C12H25NH3)2CoCl4?(C16H33NH3)2CoCl4, (C10H21NH3)2ZnCl4?(C16H33NH3)2ZnCl4 and (C12H25NH3)2ZnCl4?(C16H33NH3)2ZnCl4 were investigated by means of DSC. These six compounds and their binary mixtures can retain energies between 74 and 115 J/g during solid-state transformations at temperatures between 70 and 105°C, and they are therefore being considered for potential use in solar energy systems. 相似文献
864.
甲醛与乙醛,甲醚,硝基甲烷相互作用的从头算研究 总被引:1,自引:0,他引:1
用6-31G、全构型优化,研究了甲醛与乙醛、甲醚、硝基甲烷的相互作用。结果表明所有超分子稳定构型都包含2个C—H—O氢键的平面环状结构。H—O距离为0.228~0.264 nm,作用能为—19~—24 kJ/mol,与二聚水的作用能接近。稳定性主要取决于甲基上取代基Y吸电子能力以及环状结构中氢键张力。STO-3G不很适用于研究这类分子的相互作用。 相似文献
865.
基质辅助激光解吸附飞行时间质谱分析缩合单宁的阳离子化问题 总被引:6,自引:0,他引:6
以单价金属离子Cs 和Na 作为离子化试剂,对3种缩合单宁进行基质辅助激光解吸附飞行时间(MALD I-TOF)质谱分析。加入Na 作为阳离子化试剂,能得到较高质量的质谱图。但由于实验通道中几乎不可能完全去除的K 的干扰而会高估棓儿茶酚/表棓儿茶酚单元的组成比例,从而影响对棓儿茶酚/表棓儿茶酚单元存在与否的判断;选择Cs 作为阳离子化试剂可以避免此问题,但在复杂的缩合单宁分析中,同样因为杂质离子Na 和K 的干扰而使得质谱图变得更复杂;未去离子处理直接对缩合单宁进行MALD I-TOF质谱分析与去离子并加入Cs 的处理比去离子并加入Na 能检测到更高聚合度的高聚物,检测到离子峰强度最高的聚合物随离子不同而不同。 相似文献
866.
An amperometric cholesterol biosensor based on immobilization of cholesterol oxidase in a Prussian blue (PB)/polypyrrole (PPy) composite film on the surface of a glassy carbon electrode was fabricated. Hydrogen peroxide produced by the enzymatic reaction was catalytically reduced on the PB film electrode at 0 V with a sensitivity of 39 μA (mol/L)?1. Cholesterol in the concentration range of 10?5 ? 10?4 mol/L was determined with a detection limit of 6 × 10?7 mol/L by amperometric method. Normal coexisting compounds in the bio‐samples such as ascorbic acid and uric acid do not interfere with the determination. The excellent properties of the sensor in sensitivity and selectivity are attributed to the PB/PPy layer modified on the sensor. 相似文献
867.
A new class of M(II)–Hg(II) (M=Cu(II), Co(II), Ni(II)) mixed-metal coordination polymers, Cu(2-pyrazinecarboxylate)2HgCl2 (4), [Co(2-pyrazinecarboxylate)2(HgCl2)2] · 0.61H2O (5) and [Ni(2-pyrazinecarboxylate)2(HgCl2)2] · 0.77H2O (6), have been prepared by self assembly of metal-containing building blocks, M(2-pyrazinecarboxylate)2 · (H2O)2(M=Cu(II), Co(II), Ni(II)), with HgCl2. Compounds 4–6 were characterized fully by IR, elemental analysis and single crystal X-ray diffraction. Compound 4 crystallized in the monoclinic space group C2/c, with a=17.916(5) Å, b=7.223(2) Å, c=13.335(4) Å, β=128.726(3)°, V=1346.2(6) Å3, Z=4. It contains alternating Hg(II) and Cu(II) metal centers that are cross-linked by 2-pyrazinecarboxylate spacers and chlorine co-ligands to generate a unique three-dimensional Hg(II)–Cu(II) mixed metal framework. Compound 5 crystallized in the triclinic space group P
, with a=6.3879(7) Å, b=6.6626(8) Å, c=13.2286(15) Å, α=96.339(2)°, β=91.590(2)°, γ=113.462(2)°, V=511.71(10) Å3, Z=1. Compound 6 also crystallized in the triclinic space group P
, with a=6.3543(8) Å, b=6.6194(8) Å, c=13.2801(16) Å, α=96.449(2)°, β=92.263(2)°, γ=113.541(2)°, V=506.67(11) Å3, Z=1. Compounds 5 and 6 are isostructural and in the solid state the Hg(II)M(II)Hg(II) units are connected by Hg2Cl2 linkages to produce a novel M(II)–Hg(II) (M=Co(II), Ni(II)) zigzag mixed-metal chain, in which a new type of M–M′–M′–M array was observed. The metal containing building blocks, M(2-pyrazinecarboxylate)2 · (H2O)2 (M=Cu(II), Co(II), Ni(II)), exhibit different connectivities to HgCl2 depending on the metal cation contained within them. 相似文献
868.
Wanlong Xiao Yuhao Mo Jing Guo Zhishan Su Shunxi Dong Xiaoming Feng 《Chemical science》2021,12(8):2940
New types of C2-symmetric chiral macrodiolides are readily obtained via chiral N,N′-dioxide-scandium(iii) complex-promoted asymmetric tandem Friedel–Crafts alkylation/intermolecular macrolactonization of ortho-quinone methides with C3-substituted indoles. This protocol provides an array of enantioenriched macrodiolides with 16, 18 or 20-membered rings in moderate to good yields with high diastereoselectivities and excellent enantioselectivities through adjusting the length of the tether at the C3 position of indoles. Density functional theory calculations indicate that the formation of macrocycles is more favorable than that of 9-membered-ring lactones in terms of kinetics and thermodynamics. The potential utility of these intriguing chiral macrodiolide molecules is demonstrated in the enantiomeric recognition of aminols and chemical recognition of metal ions.An asymmetric tandem Friedel–Crafts alkylation/intermolecular macrolactonization of ortho-quinone methides with C3-substituted indoles was achieved by using a chiral N,N′-dioxide-scandium(iii) complex. 相似文献
869.
The electrooxidation of L -dopa at GC electrode was studied by in situ UV-vis spectroelectrochemistry (SEC) and cyclic voltammetry. The mechanism of electrooxidation and some reaction parameters were obtained. The results showed that the whole electrooxidation reaction of L -dopa at glassy carbon (GC) electrode was an irreversible electrochemical process followed by a chemical reaction in neutral solution (EC mechanism). The spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential E0=228 mV, the apparent electron-transfer number of the electrooxidation reaction αn=0.376 (R=0.99, SD=0.26), the standard electrochemical rate constant k0=(3.93±0.12)×10−4 cm s−1 (SD=1.02×10−2), and the formation equilibrium constant of the following chemical reaction kc=(5.38±0.34)×10−1 s−1 (SD=1.02×10−2) were also obtained. 相似文献
870.
Yun Yan GAO Chang Jiang YOU Jin Ping CHEN Yong Yong LIU Bao Wen ZHANG Yi LI* Technical Institute of Physics Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(12)
The photochemistry of the vitamin D family and their precursors has been the subject of extensive studies for many years1-4. Most of the studies focus on the photoisomer- ization of 7-dehydrocholesterol and that of tachysterol to previtamin D3, which is of commercial importance in the synthesis of vitamin D34, 5. Recently the cis/trans isomerization of vitamin D analogs (Scheme 1) draws attention because of its importance in the synthesis of hydroxylated vitamin D metabolites6. However, o… 相似文献