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991.
Nikolaos C. Papandreou Stella Makedonopoulou Ekaterini A. Antoniadou‐Vyza Irene M. Mavridis Stavros J. Hamodrakas 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o730-o732
The title salt, C18H22N5+·Cl?, is a member of a new series of lipophilic 4,6‐diamino spiro‐s‐triazines which are potent inhibitors of dihydrofolate reductase. The protonated triazine ring deviates from planarity, whereas the cyclohexane ring adopts a chair conformation. A rather unusual hydrogen‐bonding scheme exists in the crystal. There is a centrosymmetric arrangement involving two amino groups and two triazine ring N atoms, with graph‐set R(8) and an N?N distance of 3.098 (3) Å, flanked by two additional R(8) systems, involving two amino groups, a triazine ring N atom and a Cl? anion, with N?Cl distances in the range 3.179 (2)–3.278 (2) Å. Furthermore, the Cl? anion, the protonated triazine ring N atom and an amino group form a hydrogen‐bonding system with graph‐set R(6). 相似文献
992.
Zhen‐Feng Zhang Dong‐Chao Wang Jian‐Ge Wang Gui‐Rong Qu 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(9):o524-o527
The molecules of 2,2,2‐trichloro‐N,N′‐diphenylethane‐1,1‐diamine, C14H13Cl3N2, are linked into (040) sheets by a combination of C—H...Cl and C—H...π(arene) hydrogen bonds. In 2,2,2‐trichloro‐N,N′‐bis(4‐methylphenyl)ethane‐1,1‐diamine, C16H17Cl3N2, the molecules are linked into C(7) chains by two independent C—H...Cl hydrogen bonds and one Cl...Cl contact. 相似文献
993.
Vijay M. Krishnamurthy Dr. Brooks R. Bohall Chu‐Young Kim Dr. Demetri T. Moustakas Dr. David W. Christianson Prof. Dr. George M. Whitesides Prof. Dr. 《化学:亚洲杂志》2007,2(1):94-105
This paper describes a calorimetric study of the association of a series of seven fluorinated benzenesulfonamide ligands (C6HnF5?nSO2NH2) with bovine carbonic anhydrase II (BCA). Quantitative structure–activity relationships between the free energy, enthalpy, and entropy of binding and pKa and log P of the ligands allowed the evaluation of the thermodynamic parameters in terms of the two independent effects of fluorination on the ligand: its electrostatic potential and its hydrophobicity. The parameters were partitioned to the three different structural interactions between the ligand and BCA: the ZnII cofactor–sulfonamide bond (≈65 % of the free energy of binding), the hydrogen bonds between the ligand and BCA (≈10 %), and the contacts between the phenyl ring of the ligand and BCA (≈25 %). Calorimetry revealed that all of the ligands studied bind in a 1:1 stoichiometry with BCA; this result was confirmed by 19F NMR spectroscopy and X‐ray crystallography (for complexes with human carbonic anhydrase II). 相似文献
994.
Wen Lu Qin‐Yu Zhu Yong Zhang Xiao‐Min Lin Jie Dai 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):m496-m498
The title salt, bis[2,3‐bis(aminocarbonyl)‐8,9‐bis(methylsulfanyl)tetrathiafulvalenium] di‐μ‐bromido‐bis[bromidocopper(II)], (C10H10N2O2S6)2[Cu2Br4], contains 2,3‐bis(aminocarbonyl)‐8,9‐bis(methylsulfanyl)tetrathiafulvalenium radical cations, [DMT‐TTF(CONH2)2]·+, and [Cu2Br4]2− anions. The cations are associated across centres of inversion in a head‐to‐tail fashion via short face‐to‐face S...S stacking (TTF moiety). These dimers are further assembled into a one‐dimensional chain structure via interdimer double S...S contacts involving the methylsulfanyl groups. The one‐dimensional chains give rise to a two‐dimensional structure through intermolecular double N—H...O hydrogen bonds involving the amide group. The [Cu2Br4]2− anions, which straddle centres of inversion, are located between the cation layers. Electron paramagnetic resonance measurements show a radical signal, indicating that the two TTF·+ radicals are not completely coupled in the dimer. 相似文献
995.
A novel near infrared (NIR) modeling method—Laplacian regularized least squares regression (LapRLSR) was presented, which can take the advantage of many unlabeled spectra to promote the prediction performance of the model even if there are only few calibration samples. Using LapRLSR modeling, NIR spectral analysis was applied to the online monitoring of the concentration of salvia acid B in the column separation of Salvianolate. The results demonstrated that LapRLSR outperformed partial least squares (PLS) significantly, and NIR online analysis was applicable. 相似文献
996.
用巯基乙酸做稳定剂制备了水溶性CdSe纳米颗粒, 用十六烷基三甲基溴化铵(HTAB)、发光性(4-甲氧基均二苯乙烯基)二甲基乙基溴化铵 (MODAB)及末端含有双键的(4-甲基丙烯酰氧基均二苯乙烯基)二甲基乙基溴化铵(MSDAB)对该CdSe纳米颗粒进行了混合组装.通过改变三种有机分子的比例可以调控所得组装体的溶解性、聚合性及其发光性质.实验结果表明,当HTAB:MODAB:MSDAB=1:5.98~5.90:0.02~0.10(摩尔比)时,所得组装体具有较好的聚合性、溶解性和荧光性质. 相似文献
997.
Dong Han Kim Arthur A. Santilli Richard A. Fieber 《Journal of heterocyclic chemistry》1972,9(6):1347-1354
Syntheses of 11-acety1-2-phenylpyrimido[5,4-c][1,5]benzoxazepin-5(11H)one ( 16a ) and analogs ( 16b,c, 22 ) were described. The reaction of 4-chloro-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester ( 7 ) with 2-aminophenol afforded 4-(2-hydroxyanilino)-2-phenyl-5-pyrimidine-carboxylic acid ethyl ester ( 8a ). The latter was also prepared by catalytic reduction of 4-(2-nitrophenoxy)-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester ( 9 ), which was obtained from 7 and 2-nitrophenol. Involvement of 4-(2-aminophenoxy)-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester ( 12a ) in this reduction as an intermediate was demonstrated by an independent synthesis of 12a and its subsequent rearrangement to 8a. Hydrolysis of 8a or 12a gave 4-(2-hydroxyanilino)-2-phenyl-5-pyrimidinecarboxylic acid ( 15a ). Reaction of 15a with acetic anhydride afforded 16a , the first member of a novel ring system, the pyrimido[5,4- c ][1,5]-benzoxazepin. Additional examples ( 16b,c ) were prepared similarly. The corresponding 11-ethyl derivative ( 22 ) was prepared in similar fashion, starting with 7 and 2-ethylaminophenol. A possible reaction mechanism for the formation of 16a-c from 15a-c and acetic anhydride was discussed. 相似文献
998.
Electrostatic layer-by-layer assembled carbon nanotube multilayer film and its electrocatalytic activity for O2 reduction 总被引:1,自引:0,他引:1
Zhang M Yan Y Gong K Mao L Guo Z Chen Y 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8781-8785
Multilayer films of shortened multiwalled carbon nanotubes (MWNTs) are homogeneously and stably assembled on glassy carbon electrodes with the layer-by-layer (LBL) method, based on electrostatic interaction of positively charged poly(diallyldimethylammonium chloride) and negatively charged and shortened MWNTs. The film assembly and electrochemical property as well as the electrocatalytic activity toward O2 reduction of the MWNT multilayer film are studied. Scanning electron microscopy, the quartz crystal microbalance technique, ultraviolet-visible-near-infrared spectroscopy, and cyclic voltammetry are used for characterization of film assembly. Experimental results revealed that film growth is uniform, almost with the same coverage of the MWNTs in each layer, and that the assembled MWNTs are mainly in the form of small bundles or single tubes on the electrodes. Electrochemical studies indicate that the LBL assembled MWNT films possess a remarkable electrocatalytic activity toward O2 reduction in alkaline media. This property, combined with the well-dispersed, porous and conductive features of the MWNT film illustrated with the LBL method, suggests the potential application of the MWNT film for constructing an efficient alkaline air electrode for energy conversions. 相似文献
999.
Four 2-(α-hydroxyalkyl)-2-oxazolines and a 2-(α-hydroxy-α,α-diphenyl)-2-benzooxazole were synthesized from β-amimoalcohols and α-hydroxy carboxylic acids under microwave irradiation in the absence of a solvent. 相似文献
1000.
Eduardo Corts Corts Rafael Sosa Mendoza Maximiliano Santibez Gutirrez Olivia Garca‐Mellado De Corts 《Journal of heterocyclic chemistry》2004,41(2):273-276
The preparation and spectral properties often novel methyl 5‐[(o‐, m‐, and p‐substituted)‐phenylthio]‐2‐benzimidazolecarbamates with possible pharmacological activity as antihelmintics is described; by condensation and cyclization between 5‐methylthioures sulfate chloroformic acid methyl ester and 3,4‐diaminophenyl‐substituted‐phenylthio ether dissolved in ethanol. The structures of all final products were corroborated by ir; 1H‐nmr, 13C‐nmr and ms. 相似文献