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991.
Ling-Tian Tang Yu Wei Yi Wang Shao-Wen Hu Xin-Qi Liu Tai-Wei Chu Xiang-Yun Wang 《Journal of Molecular Structure》2004,686(1-3):25-30
The formation of charge-transfer (CT) complexes between N-methyl-6,7-methylenedioxy-tetrahydro-4-isoquinolone (MMDTIQ, the model molecule of alkaloids) and iodine monochloride has been studied with the density functional B3LYP method. The competition for ICl between n-donor(s) and π-donor in the same molecule has been compared for the first time. The results indicate that the electron-donating ability of various donor sites decreases in the following order: amino nitrogen>carbonyl oxygen>etheric oxygen≈aromatic ring. Complexes with a stoichiometry of 1:1 to 1:5 (MMDTIQ–ICl) might form. Among complexes with a given stoichiometry, the one in which the phenyl ring is involved in the binding is always the least stable. According to these results, in order to ensure an alkaloid iodinated, the amount of ICl should be far beyond that of alkaloids and a low polar solvent should be used, which is quite in agreement with our recent experimental results. 相似文献
992.
993.
994.
聚苯乙烯型阴离子交换剂的合成方法 总被引:5,自引:0,他引:5
对聚苯乙烯型阴离子交换剂的各种合成方法作了较为全面的评述。指出使用氯甲醚为原料的氯甲基化法由于毒性问题已经受到限制,分析了其它方法在实现工业化生产并最终取代氯甲基化法方面的可能性。 相似文献
995.
Wenhua Chen Xue Yao Zhenghui Huang Fei Mao Longfei Guan Yun Tang Hualiang Jiang Jian Li Jin Huang Lubin Jiang Jin Zhu 《中国化学快报》2019,30(1):250-254
A series of novel 2,4-diaminopyrimidine-modified compounds was designed and synthesized. Compound 14 showed micromolar dual inhibitory effect on both FP-2 and PfDHFR, and potential inhibition to the proliferation of P. falciparum 3D7 strain and chloroquine-resistant P. falciparum Dd2 strain. 相似文献
996.
A room-temperature ionic liquid (IL), 1-ethyl-3-methyl-imidazolium tetrafluoroborate (1E-3MI-TFB), used for the coating of
a silica capillary enables one to reduce or invert the electroosmotic flow (EOF) in capillary zone electrophoresis. Excellent
separations of amino acids and ary lalkanoic acids were obtained. Such separations could not be obtained in a naked capillary
in the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) or polycationic polymer hexadimethrine bromide
(HDB). The results indicate that 1E-3MI-TFB not only modulates the EOF but also acts as a discriminator. Further experiments
indicate that the interaction between hydrogen at C-2 carbon of IL and acid drugs plays an important role in the separation.
The text was submitted by the authors in English. 相似文献
997.
The catalytic effect of chiral Lewis acids on the hetero-Diels-Alder reaction between aldehydes and Danishefsky's diene (1) has been investigated. A variety of combinations of different ligands and Lewis acids have been examined as catalysts for the hetero-Diels-Alder reaction between benzaldehyde and 1, and it has been found that the readily accessible Ti(IV)-H(8)-BINOL (TiHBOL) complex is a very effective catalyst for the reaction, leading to products with very high enantioselectivity (up to 99% ee) and yield (92%). The hetero-Diels-Alder reaction of other aldehydes with 1 under the catalysis of TiHBOL is a general reaction which proceeds well with very high enantioselectivity and isolated yield for various aldehydes at 0 degrees C to room temperature. Based on the experimental results, the proposed mechanism of the hetero-Diels-Alder reaction and the dihedral angle effects of ligands are discussed. 相似文献
998.
Ab initio total energy calculations have been performed for CO chemisorption on Pd{110}. Local density approximation (LDA) calculations yield chemisorption energies which are significantly higher than experimental values but inclusion of the generalised gradient approximation (GGA) gives better agreement. In general, sites with higher coordination of the adsorbate to surface atoms lead to a larger degree of overbinding with LDA, and give larger corrections with GGA. The reason is discussed using a first-order perturbation approximation. It is concluded that this may be a general failure of LDA for chemisorption energy calculations. This conclusion may be extended to many surface calculations, such as potential energy surfaces for diffusion. 相似文献
999.
Xiao‐Yan Chen Peng Cheng Shi‐Ping Yan Dai‐Zheng Liao Zong‐Hui Jiang 《无机化学与普通化学杂志》2005,631(15):3104-3107
A novel two‐dimensional cobalt complex, [Co(btrm)2(dca)]ClO4 ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R1 = 0.0784, wR2 = 0.2041. The cobalt atom involves a six‐coordinated CoN6 environment, with a distorted octahedral coordination. Two btrm ligands connect the CoII atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated. 相似文献
1000.
Intermolecular potential energy surface and spectra of He-HCl with generalization to other rare gas-hydrogen halide complexes 总被引:3,自引:0,他引:3
A two-dimensional (rigid monomer) intermolecular potential energy surface (PES) of the He-HCl complex has been obtained from ab initio calculations utilizing the symmetry-adapted perturbation theory (SAPT) and an spdfg basis set including midbond functions. The bond length in HCl was chosen to be equal to the expectation value in the ground vibrational state of isolated HCl. The rigid-monomer potential should be a very good approximation to the complete (three-dimensional) potential for H-Cl distances corresponding to the lowest vibrational levels of the monomer since the He-HCl interaction energy was found to be only weakly dependent on the HCl bond length in this region, at least as compared to systems such as Ar-HF. The calculated points were fitted using an analytic function with ab initio computed asymptotic coefficients. As expected, the complex is loosely bound, with the dispersion energy providing the majority of the attraction. Our SAPT PES agrees with the semiempirical PES of Willey et al. [J. Chem. Phys. 96, 898 (1992)], in finding that, atypically for rare gas-hydrogen halide complexes including the lighter halide atoms, the global minimum is on the Cl side (with intermonomer separation 3.35 A and depth of 32.8 cm(-1)), rather than on the H side, where there is only a local minimum (3.85 A, 30.8 cm(-1)). The ordering of the minima was confirmed by single-point calculations in larger basis sets and complete basis set extrapolations, and also using higher levels of theory. We show that the opposite findings in the recent calculations of Zhang and Shi [J. Mol. Struct: THEOCHEM 589, 89 (2002)] are due to the lack of midbond functions in their basis set. Despite the closeness in depth of the two linear minima, the existence of a relatively high barrier between them invalidates the assumption of isotropy, a feature of some literature potentials. The trends concerning the locations of minima within the family of rare gas-hydrogen halide complexes are rationalized in terms of the physical components of the intermolecular forces and related to monomer properties. The accuracy of the SAPT PES was tested by performing calculations of rovibrational levels. The transition frequencies obtained were found to be in excellent agreement (to within 0.02 cm(-1)) with the measurements of Lovejoy and Nesbitt [J. Chem. Phys. 93, 5387 (1990)]. The SAPT PES predicts a dissociation energy for the complex of 7.74 cm(-1) which is probably more accurate than the experimental value of 10.1+/-1.2 cm(-1). Our analysis of the ground-state rovibrational wave function shows that the He-HCl configuration is favored over the He-ClH configuration despite the ordering of minima. This is due to the greater volume of the well in the former case. We have also determined positions and widths of three low-lying resonance states through scattering calculations. These predictions are expected to be more accurate than values derived from experiment. 相似文献