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7α,15α-Dibromo-8,16-diphenyl-6,7,14,15-tetrahydro-6α,14α-epithiocycloocta[1,2-b:5,6-b′]diquinoline deuterochloroform solvate
Isa Y. H. Chan,Roger Bishop,Donald C. Craig,Mohan M. Bhadbhade
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809032978
Abstract: In the racemic title compound, C34H22Br2N2S·CDCl3, pairs of diquinoline host molecules form centrosymmetric brick-like dimers utilizing three different aryl edge-to-face interactions (EF1–3). The dimeric (EF)6 (i.e. 2 × EF1–3) building blocks pack with the deuterochloroform guest molecules positioned near each of their corners. The Cl atoms of the latter are disordered over two sets of sites in a 0.53 (2):0.47 (2) ratio.
Synthesis and Crystal Structure Determination of 4’,9’,4”,9”-Tetra-t-Butyl- 1’,6’,1”,6”-Tetramethoxy-2,5-Dithia[3.3] Metabiphenylophane  [PDF]
Tetsuji Moriguchi, Tatsuya Egami, Daisuke Yakeya, Venkataprasad Jalli, Kenji Yoza, Akihiko Tsuge
Crystal Structure Theory and Applications (CSTA) , 2016, DOI: 10.4236/csta.2016.53005
Abstract: The title compound 4’,9’,4”,9”-tetra-tert-butyl-1’,6’,1”,6”-tetramethoxy-2,5-dithia[3.3] metabiphenylophane was synthesized as a calixarene like large-sized metacyclophane from the corresponding 3,3’-bis(chloromethyl)-5,5’-bis(1,1-dimethylethyl)-2,2’-dimethoxy-1,1’-biphenyl and 3,3’-bis (mercaptomethyl)-5,5’-bis(1,1-dimethylethyl)-2,2’-dimethoxy-1,1’-biphenyl via an intermolecular condensation reaction. The compound was characterized using 1H NMR spectroscopy and mass spectrometry. Its exact conformational structure was determined via single crystal X-ray diffraction analysis. The compound has quite strained 1,2-alternate like structure because of its two high dihedral angled and rigid biphenyl parts in the crystal. The crystal includes the two isomers as two different 1,2-alternate like conformers, and the ratio of the two isomers is 78:22.
Synthesis and Molecular Structure of 4′,9′,4″,9″-Tetra-tert-butyl-1′,6′,1″,6″-tetramethoxy-2,5-dioxa[3.3]metabiphenylophane  [PDF]
Tetsuji Moriguchi,Tatsuya Egami,Akihiko Tsuge
Journal of Crystallography , 2014, DOI: 10.1155/2014/695701
Abstract: A large calixarene-like metacyclophane, 4′,9′,4″,9″-tetra-tert-butyl-1′,6′,1″,6″-tetramethoxy-2,5-dioxa[3.3]metabiphenylophane, was synthesized by an intermolecular condensation reaction of its corresponding bischloromethyl-biphenyl and bishydroxymethyl-biphenyl precursors. After molecular characterization by 1H NMR spectroscopy and mass spectrometry, the compound generated single crystals by recrystallization from a dichloromethane/hexane mixture, facilitating an exact conformational determination via X-ray diffraction analysis. The crystal was found to belong to the monoclinic space group with cell parameters a = 19.908(2)??, b = 9.7193(11)??, c = 23.350(3)??, β = 109.594(1)°, and ?g/cm3 at 90?K. The compound adopted quite strained 1,2-alternate-like conformations because its biphenyl parts displayed large dihedral angles and rigidity. The crystal did not incorporate any solvent molecule but its molecular cavity and crystal space were effectively filled by the substituents. 1. Introduction Calixarenes are cyclic compounds consisting of aromatic rings and methylene bridge chains. In search for novel supramolecular hosts, numerous efforts have been deployed to decorate the upper or lower rim of calixarenes with various functional groups [1–3]. However, the nature of their cyclic skeleton clearly plays a central role in their remarkable performance as host molecules. Members of the metacyclophane family [4–8], calixarenes, are readily obtained by base-assisted condensation of tert-butylphenol and formaldehyde into methylene-based bridges exclusively. In addition, several calixarene analogues such as []metacyclophanes containing oxygen [9, 10] or nitrogen [11, 12] instead of methylene groups in their bridges have been prepared. Cyclic compounds such as calix[4]arenes and large metacyclophanes present various conformations derived from the orientations of the aromatic parts [13]. In addition, the crystal structures of several cyclophanes have been reported using an alternative synthetic pathway [14] and cesium ion template effect [15–19]. Although large metacyclophanes comprising ether bridges and biphenyl units have been synthesized and their host-guest properties were reported [20, 21], their structures in the crystals were not determined. In this study, we report the synthesis of “oxametabiphenilophanes,” a new class of metacyclophanes that incorporate oxygen atoms in bridges and two biphenyl parts thus giving rigidity to the molecules (Scheme 1). A precursor mixture of bischloromethyl-biphenyl and bishidroxymethyl-biphenyl reacted under alkaline
Luis Ángel Garza Rodríguez,Sylvain Bernès,Perla Elizondo Martínez,Blanca Nájera Martínez
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810006033
Abstract: The title molecule, C23H15N3, is a terpyridine derivative resulting from the Friedl nder annulation between 2,6-diacetylpyridine and N,N′-bis(2-aminobenzyl)ethylenediamine. The asymmetric unit contains one half-molecule, the complete molecule being generated by a mirror plane (one N atom and one C atom lie on the plane). The molecule, although aromatic, is deformed from planarity as a result of crystal packing forces: molecules are stacked along the short c axis, with a short separation of 3.605 (1) between the mean planes. The bent molecular shape is reflected in the dihedral angle of 16.10 (5)° between the essentially planar quinoline groups. In addition to π...π interactions, the crystal structure features weak inter-stack C—H...N contacts involving atoms of the central pyridine rings which lie in a common crystallographic m plane.
Xingxun Zhu,Ming Hu
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810028874
Abstract: In the title compound, C16H14Br2S2 [systematic name: 12,52-dibromo-2,7-dithia-1,5(1,4)-dibenzenaoctaphane], the centroids of the two benzene rings are separated by 3.313 (5) . The crystal packing exhibits weak intermolecular S...S contacts of 3.538 (2) .
New lower bounds of classical Ramsey numbers R(6,12), R(6,14) and R(6,15)

科学通报(英文版) , 1998,
科学通报 , 1998,
Abstract: 确定Ramsey数是组合数学和图论中非常著名的难题,经过好几代数学家的努力,再加上计算机的帮助,迄今为止计算出来的型如R(k,l)的不平凡的经典Ramsey数总共只有9个1].关于Ramsey数R(6,l),在R(6,3)=182]之后,进展极其缓慢.在文献1]中,记录了迄今已知的最好的下界:R(6,4)≥35,R(6,5)≥58和R(6,6)≥102.当l≥7时至今尚未有人探索得到较好的结果,人们仅能利用递推公式3]R(k,l1)≥s且R(k,l2)≥tR(k,l1 l2-1)≥s t-1.  根据上述已知结果和熟知的平凡的R(6,2)=6,得到一些平凡的下界:l7891011R(6,…
经典Ramsey数R(6,12),R(6,14)和R(6,15)的新下界  [PDF]
科学通报 , 1998,
5,6,7,5′-Tetramethoxy-3′,4′-methylenedioxyflavone monohydrate  [cached]
Hou-Jin Li,Da-Lang Zhou,Ting-Juan Xu,Chi-Keung Lam
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812015139
Abstract: The title compound [systematic name: 5,6,7-trimethoxy-2-(7-methoxy-1,3-dihydro-2-benzofuran-5-yl)-4H-chromen-4-one monohydrate], C20H18O8·H2O, was isolated from the popular Chinese medicinal plant Entada phaseoloides. In the crystal, inversion-related molecules are joined by pairs of weak C—H...O hydrogen bonds. The dimers are further interconnected by a bridging water molecule via weak C—H...Owater and pairs of (O—H)water...O hydrogen bonds into a linear tape running parallel to the b axis.
Akira Ohta,Kazuki Hattori,Takeshi Kawase,Takashi Kobayashi
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812033119
Abstract: Molecules of the title compound, C18H16O6, are almost planar [maximum deviation = 0.096 (4) ] and reside on crystallographic centres of inversion. They adopt a conformation in which the Cmethyl—O bonds are directed along the molecular short axis [C—C—O—C torsion angles of 175.3 (3) and 178.2 (3)°]. In the crystal, molecules adopt a slipped-parallel arrangement with π–π stacking interactions along the a axis with an interplanar distance of 3.392 (4) . Weak C—H...O interactions link the molecules into sheets parallel to (10-2).
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