共查询到20条相似文献,搜索用时 31 毫秒
1.
Goverdhan Mehta Saikat Sen Siddharth Dey 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(6):o358-o360
In the title compound, C6H12O4·H2O, 1,4/2,5‐cyclohexanetetrol and water molecules are seen to possess twofold symmetry. All four hydroxyl groups of the tetrol participate in extensive intermolecular O—H⋯O hydrogen bonding to form molecular tapes propagating along the a axis. Translationally related tapes along the c axis are held together by four coordinated water molecules. 相似文献
2.
A new method for linear polymerization of maleimides via the Diels–Alder reaction has been developed. This method involves use of a new cross‐linking agent, benzene‐3,4‐dimethylenesuccinimide, which can be generated in situ from its thiophene precursor, benzene‐2,5‐dihydrothiophene‐3,4‐dicarboximide‐S,S‐dioxide. This new cross‐linking agent is reasonably reactive, readily prepared, and stable at room temperature. A controlled molecular weight oligomer has been synthesized and applied to the polymerization to yield a highly thermal stable polyimide. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:648–652, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20249 相似文献
3.
4.
Martin Lutz Jan van Krieken 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(8):o401-o405
The dimeric condensation product of lactic acid, namely (S,S)‐2‐[(2‐hydroxypropanoyl)oxy]propanoic acid, C6H10O5, (I), crystallizes with two independent molecules in the asymmetric unit, which both have an essentially planar backbone. The trimeric condensation product, namely (S,S,S)‐3‐hydroxybut‐3‐en‐2‐yl 2‐[(2‐hydroxypropanoyl)oxy]propanoate, C9H14O7, (II), has one molecule in the asymmetric unit and consists of two essentially planar parts, with the central C—O bond in a gauche conformation. Both molecules of the dimer are involved in intermolecular hydrogen bonds, forming chains with a C(8) graph set. These chains are connected by D(2) hydrogen bonds to form a two‐dimensional layer. The trimer forms hydrogen‐bonded C(10) and C22(6) chains, which together result in a two‐dimensional motif. The Hooft method [Hooft, Straver & Spek (2008). J. Appl. Cryst. 41 , 96–103] was successfully applied to the determination of the absolute structure of (I). 相似文献
5.
Ove Alexander Hgmoen strand Zeshan Iqbal Marcel Sandberg Eili T. Kase Carl Henrik Grbitz Pl Rongved 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(6):647-650
(2S,3S)‐2,6‐Dimethylheptane‐1,3‐diol, C9H20O2, (I), was synthesized from the ketone (R)‐4‐benzyl‐3‐[(2R,3S)‐3‐hydroxy‐2,6‐dimethylheptanoyl]‐1,3‐oxazolidin‐2‐one, C19H27NO4, (II), containing C atoms of known chirality. In both structures, strong hydrogen bonds between the hydroxy groups form tape motifs. The contribution from weaker C—H...O hydrogen bonds is much more evident in the structure of (II), which furthermore contains an example of a direct short Osp3...Csp2 contact that represents a usually unrecognized type of intermolecular interaction. 相似文献
6.
Visualizing the Stoichiometry of Industrial‐Style Co‐Mo‐S Catalysts with Single‐Atom Sensitivity
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yuanyuan Zhu Quentin M. Ramasse Michael Brorson Poul G. Moses Lars P. Hansen Christian F. Kisielowski Stig Helveg 《Angewandte Chemie (International ed. in English)》2014,53(40):10723-10727
The functional properties of transition metal dichalcogenides (TMDs) may be promoted by the inclusion of other elements. Here, we studied the local stoichiometry of single cobalt promoter atoms in an industrial‐style MoS2‐based hydrotreating catalyst. Aberration‐corrected scanning transmission electron microscopy and electron energy loss spectroscopy show that the Co atoms occupy sites at the (?100) S edge terminations of the graphite‐supported MoS2 nanocrystals in the catalyst. Specifically, each Co atom has four neighboring S atoms that are arranged in a reconstructed geometry, which reflects an equilibrium state. The structure agrees with complementary studies of catalysts that were prepared under vastly different conditions and on other supports. In contrast, a small amount of residual Fe in the graphite is found to compete for the S edge sites, so that promotion by Co is strongly sensitive to the purity of the raw materials. The present single‐atom‐sensitive analytical method therefore offers a guide for advancing preparative methods for promoted TMD nanomaterials. 相似文献
7.
Henning Lühmann Enrique Quiroga‐Gonzlez Lorenz Kienle Viola Duppel Gero Neubüser Wolfgang Bensch 《无机化学与普通化学杂志》2019,645(3):198-206
Solvothermal syntheses of copper‐indium‐sulfides performed with different Cu:In:S ratios afforded crystallization of nanocrystalline Cu‐In‐S phases with compositions close to CuInS2, CuIn3S5, and CuIn7S11. Each sample shows a different and distinguishable morphology. The minority component CuInS2 with wurtzite‐type structure crystallizes as thin plates, which are preferably stacked parallel to black stacks. The component with composition CuIn3S5 forms isolated few nm thin layers being arranged like the petals of a flower growing from a common point. Finally, red CuIn7S11 is obtained as nanobelts with individual diameters of about 20 nm and lengths up to more than 1 μm. According to electron diffraction patterns and X‐ray diffractometry the structures of CuIn3S5 and CuIn7S11 cannot be assigned to known bulk phases of the Cu‐In‐S system, however first structure models are proposed. 相似文献
8.
Maria Gdaniec Elbieta Nowak Maria J. Milewska Tadeusz Pooski 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(11):o661-o662
The molecule of the title compound, C8H11NO2, contains a strained bicyclic system with a significantly twisted imide chromophore. The five‐membered ring fragment containing the imide function is strongly puckered and adopts a half‐chair conformation. The six‐membered ring has a slightly distorted chair conformation. The molecules are joined by strong N—H?O and weak C—H?O hydrogen bonds into infinite chains. 相似文献
9.
Andrzej Gzella Maria D. Rozwadowska 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):981-982
The absolute configuration of the title compound, alternatively called (+)‐(4,5‐dihydro‐2,5‐diphenyloxazol‐4‐yl)methanol, C16H15NO2, has been confirmed as 4S,5S. The hydroxymethyl group and phenyl ring at the asymmetric C atoms exhibit β and α orientations, respectively. The exocyclic C—C bonds at the asymmetric C atoms are mutually anticlinal (?ac). The hydroxyl group and the N atom of the oxazoline ring are involved in an intermolecular hydrogen bond leading to chains of molecules. 相似文献
10.
11.
Shiv Chand Anand Kumar Pandey Rahul Singh Saurabh Kumar Krishna Nand Singh 《化学:亚洲杂志》2019,14(24):4712-4716
An operationally simple Eosin Y catalyzed sulfenylation of hydrazones has been realized to afford a range of thioethers under visible light. The methodology provides high yields of thioethers under ambient conditions employing readily available and inexpensive starting materials. The reaction has broad substrate scope and is compatible with various functional groups. 相似文献
12.
Udo Beckmann Sally Brooker 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(11):o653-o655
The structure of the cocrystallized 1:1 adduct of (S,S)‐4‐amino‐3,5‐bis(1‐hydroxyethyl)‐1,2,4‐triazole and (S,S)‐1,2‐bis(2‐hydroxypropionyl)hydrazine, C6H12N4O2·C6H12N2O4, has tetragonal symmetry. All eight O‐ and N‐bound H atoms are involved in intermolecular hydrogen bonds, resulting in infinite zigzag chains of the triazole molecules, with the hydrazine molecules filling the gaps between the chains and completing a three‐dimensional hydrogen‐bonded array. 相似文献
13.
(S,S)‐2‐Substituted‐4,4‐diphenyl‐3,1‐oxazabicyclo[3.3.0]octanes were synthesized diaster‐eospecifically from aldehydes and (S)‐2‐(hydroxydiphenylmethyl)pyrrolidine, which was obtained from L ‐proline, under acid‐catalyzed conditions in anhydrous toluene. The stereospecificity of the condensation reaction is discussed. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:42–45, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10064 相似文献
14.
Circularly polarized luminescence (CPL), the differential emission of left‐ and right‐handed circularly polarized light from a molecule, is modeled by using time‐dependent density functional theory. Calculations of the CPL spectra for the first electronic excited states of d‐camphorquinone and (S,S)‐trans‐β‐hydrindanone under the Franck–Condon approximation and using various functionals are presented, as well as calculations of absorption, emission, and circular dichroism spectra. The functionals B3LYP, BHLYP, and CAM‐B3LYP are employed, along with the TZVP and aug‐cc‐pVDZ Gaussian‐type basis sets. For the lowest‐energy transitions, all functionals and basis sets perform comparably, with the long‐range‐corrected CAM‐B3LYP better reproducing the excitation energy of camphorquinone but leading to a blue shift with respect to experiment for hydrindanone. The vibrationally resolved spectra of camphorquinone are very well reproduced in terms of peak location, widths, shapes, and intensities. The spectra of hydrindanone are well reproduced in terms of overall envelope shape and width, as well as the lack of prominent vibrational structure in the emission and CPL spectra. Overall the simulated spectra compare well with experiment, and reproduce the band shapes, emission red shifts, and presence or absence of visible vibrational fine structure. 相似文献
15.
F. Sbai M. Dakir A. Auhmani H. El Jamili M. Akssira A. Benharref A. Kenz M. Pierrot 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(8):o518-o520
The stereochemistries of the title compounds, both C16H24Cl2O, have been established by X‐ray diffraction. In both structures, the seven‐membered ring adopts the same conformation, whereas the six‐membered ring shows an envelope conformation in the epoxydodecane structure and a boat conformation in the dodecan‐9‐one structure. 相似文献
16.
The cyclic [2R,S(R)]‐bornane‐10,2‐sulfinamide (−)‐ 2b , an analogue of Oppolzer`s camphor‐derived sultam (−)‐ 2a , was synthesized by reduction of the known N‐alkylidenesulfinamide (+)‐ 1b with NaBH4. The uncatalyzed [4+2] cycloaddition of cyclopentadiene to the methyl ester (−)‐ 3b of the N‐fumaroylsulfinamide, obtained from (−)‐ 2b , proceeds with lower endo and π‐facial selectivity as compared to dienophiles (−)‐ 3a , c . In contrast to these latter, the diastereoselectivity is reversed either in apolar CCl4 or in the presence of TiCl4. This inversion is explained by a competitive C(α)‐si addition on the reactive anti‐s‐trans conformer. 相似文献
17.
Jonghee Lee Jeong‐Ik Lee Moo‐Jin Park Young Kwan Jung Nam Sung Cho Hoon Je Cho Do‐Hoon Hwang Sang‐Kyu Lee Jong‐Hwa Park Jiwon Hong Hye Yong Chu Hong‐Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1236-1246
A novel series of poly(10‐hexyl‐phenothiazine‐S,S‐dioxide‐3,7‐diyl) and poly(9,9′‐dioctyl‐fluorene‐2,7‐diyl‐alt‐10‐hexyl‐3,7‐phenothiazine‐S,S‐dioxide) (PFPTZ‐SS) compounds were synthesized through Ni(0)‐mediated Yamamoto polymerization and Pd(II)‐catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ‐SS compounds were highly fluorescent with bright blue emissions in the solid state. Light‐emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish‐blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine‐S,S‐dioxide property, triggered by the introduction of an electron‐deficient SO2 unit into the electron‐rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ‐SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236–1246, 2007 相似文献
18.
Stereoselective Total Synthesis of (3S,5S)‐1,7‐Bis(4‐hydroxyphenyl)heptane‐3,5‐diol, (3S,5S)‐Alpinikatin,and Its Diastereoisomers
下载免费PDF全文
![点击此处可从《Helvetica chimica acta》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kunuru Venkatesham Sudina Purushotham Reddy Baggu Chinnababu Katragadda Suresh Babu 《Helvetica chimica acta》2015,98(9):1307-1314
Stereoselective synthesis of the diarylheptanoids, (3S,5S)‐1,7‐bis(4‐hydroxyphenyl)heptane‐3,5‐diol ( 1 ), (3S,5S)‐alpinikatin ( 3 ), and their diastereoisomers ( 2 and 4 , resp.), was achieved from readily available 4‐hydroxybenzaldehyde. The synthetic sequences involve Browns's allylation and Et2Zn mediated diastereoselective alkynylation reaction as key steps. 相似文献
19.
Jarno Kansikas Kaija Sipil 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1383-1385
In the synthesis of 1‐phenyl‐2‐phenylthio‐2‐(tetrahydropyran‐2‐ylthio)ethanol, C19H22O2S2, four diastereoisomers are formed. Two non‐centrosymmetric enantiomeric forms which crystallize in space groups P212121 and Pna21 are presented. The former has an intramolecular hydrogen bond between the hydroxyl group and the O atom of the tetrahydropyran ring. In the latter isomer, the hydroxyl group forms an intermolecular hydrogen bond to the O atom of the tetrahydropyranyl group of a neighbouring molecule, joining the molecules into chains in the c‐axis direction; the O?O distances are 2.962 (4) and 2.764 (3) Å, respectively. The tetrahydropyran rings are in chair conformations in both isomers and the S side chain has an equatorial orientation in the former, but an axial orientation in the latter molecule. 相似文献
20.
T. Nakahodo E. Horn E. R. T. Tiekink 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1316-1318
The Cu atom in [Cu(C7H4NOS)(C7H5NOS)(C18H15P)2] is tetrahedrally coordinated by a P2S2 donor set. One S atom is derived from neutral benzoxazole‐2‐thione and the other from the deprotonated form of the ligand. The two sulfur ligands are connected via an N—H?N interaction, leading to the formation of an eight‐membered ring. 相似文献