共查询到20条相似文献,搜索用时 15 毫秒
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Britt Friis-Jensen Sten Rettrup C. R. Sarma 《International journal of quantum chemistry》1997,64(4):421-426
The classes of the symmetric group 𝒮N are identified by partitions of N. In this work an indexing scheme is presented which provides a dense enumeration of the classes of 𝒮N. The method is based on a graphical representation of partitions of N, which also enables the determination of the class corresponding to a given number. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64 : 421–426, 1997 相似文献
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Hideyuki Tabata Natsuki Kubo Tsunehisa Okuno 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(12):o492-o495
The title compound, C28H20N2O2, forms two conformational polymorphs, (I) and (II), where the molecular structures are similar except for the orientation of the two hydroxy groups. In (I), which was obtained by slow evaporation from chloroform, the two hydroxy groups have an anti conformation. The molecules form a sheet structure within the ac plane, where the hydroxy groups form zigzag hydrogen bonds. In (II), which was obtained by slow evaporation from acetonitrile, the two hydroxy groups have a syn conformation. The molecules form a double‐sheet structure within the ab plane, where the hydroxy groups form 4‐helix hydrogen bonds. 相似文献
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Giuseppe Bruno Archimede Rotondo Lidia De Luca Silvio Sammartano Francesco Nicol 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(4):o287-o289
In the title compound, C6H18N22+·C4H4O42−·C4H6O4, the components lie on centres of symmetry in space group , such that the asymmetric unit contains three half‐molecules. Despite the different mode (with respect to other dicarboxylic acids) adopted by the intermolecular self‐interaction of succinic acid derivatives, the overall structure of the title compound consists of anionic layers that are typical of the packing structures exhibited by other dicarboxylic acid analogues. 相似文献
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A new CuII–azide complex, {(C4H12N2)[Cu5(N3)12]·4H2O}n, has been synthesized by the reaction of piperazine, Cu(OAc)2·2H2O (OAc is acetate) and NaN3. In the structure, μ2‐1,1‐ and μ3‐1,1,1‐azide anions bridge five CuII cations to form a linear pentanuclear cluster unit, which is further linked by μ2‐1,1‐ and μ2‐1,3‐azide anions to form a two‐dimensional condensed [Cu5(N3)12]n layer. The diprotonated piperazine and the solvent water molecules are hydrogen bonded to the coordination layers to form a three‐dimensional supramolecular network. 相似文献
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Qing‐An Qiao Zheng‐Ting Cai Da‐Cheng Feng Yuan‐Sheng Jiang 《International journal of quantum chemistry》2005,101(1):33-39
The mechanism of one‐carbon unit transfer between 1‐methyl‐5‐amino‐4‐carboxamide imidazole (M‐AICA) and N1‐methyl‐N1‐acryloyl‐formamide (the model molecule of 10‐f‐H4F) is investigated by the Hartree–Fock and DFT methods, respectively, at the 6‐31G* basis level. There are two different channels for the proton transfer, resulting in two reaction pathways with different properties. The results indicate that both channels can complete the reaction, but path a is slightly favored due to its lower active energy barrier. Furthermore, the influence of 4‐carboxamindde in M‐AICA is also discussed. This group can stabilize the reactant and intermediates, and reduce the active energy barrier through the intermolecular hydrogen bond. The intermolecular hydrogen bond results in an enlarged conjugation system and makes the transition states more stable. Our results are in agreement with experiments. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
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Alexander S. Lyakhov Dmitry O. Ivashkevich Sergei V. Voitekhovich Pavel N. Gaponik 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):m563-m564
The title compound, [CuCl2(C5H11N5)], is the first structurally characterized molecular chelate complex involving an α‐aminoalkyltetrazole. There are two complex molecules in the asymmetric unit. The ligand molecules are bidentate. Both Cu atoms reveal rather distorted square‐planar coordinations. The complex molecules are linked together by van der Waals interactions only. 相似文献
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Pernille Harris Pauli Kofod Yong Sheng Song Erik Larsen 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(2):m58-m60
In the title compound, [Co(C6H15N3)(C7H15N2S)]S2O6·H2O, the Co—C bond distance is 1.9930 (13) Å, which is shorter than for related compounds with the linear 1,6‐diamino‐3‐thiahexan‐4‐ide anion in place of the macrocyclic 1‐thia‐4,7‐diazacyclodecan‐8‐ide anion. The coordinated carbanion produces an elongation of 0.102 (7) Å of the Co—N bond to the 1,4,7‐triazacyclononane N atom in the trans position. This relatively small trans influence is presumably a result of the triamine ligand forming strong bonds to the CoIII atom. 相似文献
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Serkan Soylu Murat Ta Hanife Saraolu Hümeyra Bat Nezihe alkan Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o702-o704
In the title compounds, C18H20N2O2, (I), and C14H11N3O4·0.5H2O, (II), respectively, the oxime groups have an E configuration. In (I), the molecules exist as polymers bound by intermolecular C—H⋯O and O—H⋯N hydrogen bonds around inversion centres. In (II), intermolecular OW—H⋯N, OW—H⋯O and O—H⋯OW interactions stabilize the molecular packing. 相似文献
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Padmanabhan Sudhakar Govindarajan Sundararajan 《Journal of polymer science. Part A, Polymer chemistry》2006,44(13):4006-4014
The ring‐opening reaction of (S)‐N‐tosyl‐2‐phenylaziridine by benzylamine in ethanol at 80 °C resulted in the formation of the (S,S)‐bis(N‐tosyl‐2‐amino‐2‐phenylethyl)benzylamine ligand in a 60% yield. The corresponding titanium complex, 1‐TiCl2, was prepared by the reaction of the dilithiated parent ligand with TiCl4. This precatalyst, in combination with methylaluminoxane, was capable of polymerizing 1‐hexene with good activities, resulting in the formation of good yields of low‐dispersity, high‐molecular‐weight polymers at low temperatures but higher yields of lower molecular weight polymers at higher temperatures. 1H and 13C NMR spectra of the polymers suggested high isotacticity and predominant chain termination via β‐hydride elimination. The enantiomerically pure catalysts, (R,R)‐1‐TiCl2 and (S,S)‐1‐TiCl2, showed nearly identical polymerization results at various polymerization temperatures. However, when the catalyst was prepared from a racemic ligand, the obtained polymers had lower molecular weights with a bimodal distribution. This observation suggested diastereomeric aggregation of the racemic catalyst, which was well supported by the NMR studies, and a modified Arrhenius plot (the natural logarithm of the number‐average molecular weight vs the reciprocal of the temperature) also showed sigmoidal behavior, indicating the existence of two or more active species. Analogous zirconium precatalysts showed similar results in the polymerization of 1‐hexene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4006–4014, 2006 相似文献
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The title reaction, which is spin‐forbidden for N2(X1∑) + NO(X2Π) production, has been studied from 960 to 1130 K in a high‐temperature photochemistry reactor. No reaction could be observed, indicating k < 1 × 10?15 cm3 molecule?1 s?1. It is concluded that there is no significant contribution from the spin‐allowed exothermic path leading to N2(X1∑) + NO(a4Π). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 387–389, 2001 相似文献
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Ammasai Karthikeyan Robert Swinton Darious Packianathan Thomas Muthiah Franc Perdih 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(11):985-990
Two novel cocrystals of the N(7)—H tautomeric form of N6‐benzoyladenine (BA), namely N6‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (3HPA) (1/1), C12H9N5O·C6H5NO3, (I), and N6‐benzoyladenine–DL‐tartaric acid (TA) (1/1), C12H9N5O·C4H6O6, (II), are reported. In both cocrystals, the N6‐benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring‐motif heterosynthon [graph set R22(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph set R22(4)]. Both crystal structures are further stabilized by π–π stacking interactions. 相似文献
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Enrique Espinosa Michel Meyer David Berard Roger Guilard 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):m119-m121
The crystal structure of the title copper(II) complex, [Cu(C18H36N8O4)]SO4·4.5H2O, formed with the tetraamide cyclam derivative 2‐(4,8,11‐triscarbamoylmethyl‐1,4,8,11‐tetraazacyclotetradec‐1‐yl)acetamide (TETAM), is described. The macrocycle lies on an inversion centre occupied by the hexacoordinated Cu atom. The four macrocyclic tertiary amines form the equatorial plane of an axially Jahn–Teller elongated octahedron. Two O atoms belonging to two diagonally opposite amide groups occupy the apical positions, giving rise to a trans‐III stereochemistry, while both the remaining pendant side arms extend outwards from the macrocyclic cavity and are engaged in hydrogen bonds with sulfate anions and co‐crystallized water molecules. 相似文献
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Jun Luo Xin‐Rong Zhang Li‐Li Cui Wei‐Quan Dai Bao‐Shu Liu 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(12):m614-m616
The two new title complexes, [Mn(C5H3N6)2(H2O)2] and [Zn(C5H3N6)2(H2O)2], are isomorphous. In both compounds, the metal atom is located on an inversion center and is coordinated by four N atoms from two 5‐(pyrazin‐2‐yl)‐1H‐tetrazolate anions in the basal plane and by two O atoms of water ligands in the apical positions to form a distorted octahedral geometry. Intermolecular hydrogen‐bond interactions between the uncoordinated N atoms of the tetrazolate anions and the H atoms of the water molecules lead to the formation of a three‐dimensional network. 相似文献