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1.
《Magnetic resonance in chemistry : MRC》2002,40(9):589-594
The 31P chemical shift (CS) tensors of the 1,3,2‐diazaphospholenium cation 1 and the P‐chloro‐1,3,2‐diazaphospholenes 2 and 3 and the 31P and 19F CS tensors of the P‐fluoro‐1,3,2‐diazaphospholene 4 were characterized by solid‐state 31P and 19F NMR studies and quantum chemical model calculations. The computed orientation of the principal axes system of the 31P and 19F CS tensors in the P‐fluoro compound was found to be in good agreement with experimentally derived values obtained from evaluation of P–F dipolar interactions. A comparison of the trends in the chemical shifts of 1 – 4 with further available literature data confirms that the unique high shielding of δ11 in the cation 1 can be related to the effective π‐conjugation in the five‐membered heterocycle, and that a further systematic decrease in δ11 for the P‐halogen derivatives 2 – 4 is attributable to the increased perturbation of the π‐electron distribution by interaction with the halide donor. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
For asymmetric guest molecules in urea, the end‐groups of two adjacent guest molecules may arrange in three different ways: head–head, head–tail and tail–tail. Solid‐state 1H and 13C NMR spectroscopy is used to study the structural properties of 1‐bromodecane in urea. It is found that the end groups of the guest molecules are randomly arranged. The dynamic characteristics of 1‐bromodecane in urea inclusion compounds are probed by variable‐temperature solid‐state 2H NMR spectroscopy (line shapes, spin–spin relaxation: T2, spin‐lattice relaxation: T1Z and T1Q) between 120 K and room temperature. The comparison between the simulation and experimental data shows that the dynamic properties of the guest molecules can be described in a quantitative way using a non‐degenerate three‐site jump process in the low‐temperature phase and a degenerate three‐site jump in the high‐temperature phase, in combination with the small‐angle wobbling motion. The kinetic parameters can be derived from the simulation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
3.
M. Jayakannan S. Annu S. Ramalekshmi 《Journal of Polymer Science.Polymer Physics》2005,43(11):1321-1331
The solid‐state three‐dimensional ordering of polyaniline–dopant complexes was investigated with four structurally different sulfonic acid dopants. The doped materials were produced in three different ways: polyaniline emeraldine base doped with sulfonic acid (aqueous route), in situ polymerization at the organic–water solvent interface (interfacial route), and in situ polymerization in organic and aqueous solvent mixtures (bilayer route). p‐Toluenesulfonic acid (PTSA), 5‐sulfosalicilic acid (SSA), camphorsulfonic acid (CSA), and dodecylbenzene sulfonic acid (DBSA) were employed as dopants. The conductivity of the aqueous‐route samples showed 10 and 100 times higher conductivity than the interfacial and bilayer routes, respectively. WXRD studies suggested that the crystallinity of the doped samples was dependent on both the structure of the dopants and the polymerization techniques. DBSA increases the polyaniline interplanar distance and produced highly crystalline materials via the aqueous and bilayer routes but failed with the interfacial route because of poor solubility in water. CSA, PTSA, and SSA produced highly crystalline samples by the interfacial route but failed with the aqueous (except for CSA) and bilayer routes. SEM analysis revealed that the doped materials of the interfacial route had excellent continuous morphology and uniform submicrometer‐size particle distributions in comparison with those of the aqueous and bilayer routes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1321–1331, 2005 相似文献
4.
Kenta Tanaka Kanako Nakamura Nariyoshi Yoshioka Atsushi Kameyama Tetsutaro Igarashi Tadamitsu Sakurai 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):2859-2865
This study explored the abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds, which absorb long‐wavelength light (>350 nm), to photochemically initiate radical and cationic polymerizations. It was found that the irradiation of the title compounds initiates the radical polymerization of styrene whereas the cationic polymerization of oxetane proceeds in the presence of these photoinitiators to a negligible extent. The behavior of 9‐anthrylmethyloxyl and amidyl radicals in the photopolymerization process of styrene was discussed based on 1H NMR, UV, and fluorescence spectral data. In addition, the photoinitiation ability of the anthrylmethyloxyl end group was also investigated by using its model compound. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2859–2865, 2004 相似文献
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6.
Abdel‐Zaher A. Elassar 《Journal of heterocyclic chemistry》2011,48(2):272-278
Rapid synthesis of 3‐cyano‐4,6‐dimethyl‐2‐pyridone 3 , using piprazine as a catalyst was reported. X‐ray data of the 4,6‐dimethyl‐2‐oxo‐1,2‐dihydropyridine‐3‐carbonitrile exhibited its oxo form. Synthesis of isoquinolinecarbonitrile and pyridylpyridazine using compound 3 was investigated. Reactivity of the synthesized pyridone toward different organic reagents was also studied. J. Heterocyclic Chem., (2011). 相似文献
7.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(7):807-815
The supramolecular structural features of organic molecules are very important with regard to their widespread properties in both solids and solutions. Herein, we describe the synthesis of a novel multifunctional 2‐pyridone derivative, namely 6‐(4‐chlorophenyl)‐5‐formyl‐4‐methylsulfanyl‐2‐oxo‐1,2‐dihydropyridine‐3‐carbonitrile, C14H9ClN2O2S, denoted P1 , and its structural features were established through X‐ray crystallography. A Hirshfeld surface analysis followed by a two‐dimensional fingerprint plot analysis was carried out. A frontier molecular orbital investigation and natural bond orbital (NBO) calculations explored the charge‐transfer interactions associated with the molecular system. The optical properties of the 2‐pyridone derivative were elucidated through UV–Vis absorption and emission spectroscopy, indicating a strong blue emissive nature with a colour purity of 82.5%, a short‐lived lifetime and a large Stokes shift. Time‐dependent density functional theory (TD‐DFT) was used to gain some insight into the absorption behaviour and emissive characteristics of P1 . 相似文献
8.
Frank Seela Simone Budow Henning Eickmeier Hans Reuter 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):o54-o57
The title compound, 4‐amino‐1‐(2‐deoxy‐β‐d ‐erythropentofuranosyl)‐5‐(prop‐1‐ynyl)pyrimidin‐2(1H)‐one, C12H15N3O4, shows two conformations in the crystalline state which differ mainly in the glycosylic bond torsion angle and the sugar pucker. Both molecules exhibit an anti glycosylic bond conformation, with torsion angles χ = −135.0 (2) and −156.4 (2)° for molecules 1 and 2, respectively. The sugar moieties show a twisted C2′‐endo sugar pucker (S‐type), with P = 173.3 and 192.5° for molecules 1 and 2, respectively. The crystal structure is characterized by a three‐dimensional network that is stabilized by several intermolecular hydrogen bonds between the two conformers. 相似文献
9.
Edgar Marquez Tania Cordova Gabriel Chuchani 《International journal of quantum chemistry》2012,112(3):724-730
The mechanism of the gas‐phase elimination kinetics of 2‐ethoxypyridine has been studied through the electronic structure calculations using density functional methods: B3LYP/6‐31G(d,p), B3LYP/6‐31++G(d,p), B3PW91/6‐31G(d,p), B3PW91/6‐31++G(d,p), MPW1PW91/6‐31G(d,p), MPW1PW91/6‐31++G(d,p), PBEPBE/6‐31G(d,p), PBEPBE/6‐31++G(d,p), PBE1PBE1/6‐31G(d,p), and PBE1PBE1/6‐31++G(d,p). The elimination reaction of 2‐ethoxypyridine occurs through a six‐centered transition state geometry involving the pyridine nitrogen, the substituted carbon of the aromatic ring, the ethoxy oxygen, two carbons of the ethoxy group, and a hydrogen atom, which migrates from the ethoxy group to the nitrogen to give 2‐pyridone and ethylene. The reaction mechanism appears to occur with the participation of π‐electrons, similar to alkyl vinyl ether elimination reaction, with simultaneous ethylene formation and hydrogen migration to the pyridine nitrogen producing 2‐pyridone. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
10.
Albert Jeyakumar Han Goossens Bart Noordover Manoranjan Prusty Matthias Scheibitz Cor Koning 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):5118-5129
Copolyamides based on polyamide‐6,6 (PA‐6,6) were prepared by solid‐state modification (SSM). Para‐ and meta‐xylylenediamine were successfully incorporated into the aliphatic PA‐6,6 backbone at 200 and 230 °C under an inert gas flow. In the initial stage of the SSM below the melting temperature of PA‐6,6, a decrease of the molecular weight was observed due to chain scission, followed by a built up of the molecular weight and incorporation of the comonomer by postcondensation during the next stage. When the solid‐state copolymerization was continued for a sufficiently long time, the starting PA‐6,6 molecular weight was regained. The incorporation of the comonomer into the PA‐6,6 main chain was confirmed by size exclusion chromatography (SEC) with ultraviolet detection, which showed the presence of aromatic moieties in the final high‐molecular weight SSM product. The occurrence of the transamidation reaction was also proven by 1H nuclear magnetic resonance (NMR) spectroscopy. As the transamidation was limited to the amorphous phase, this SSM resulted in a nonrandom overall structure of the PA copolymer as shown by the degree of randomness determined using 13C NMR spectroscopy. The thermal properties of the SSM products were compared with melt‐synthesized copolyamides of similar chemical composition. The higher melting and higher crystallization temperatures of the solid state‐modified copolyamides confirmed their nonrandom, block‐like chemical microstructure, whereas the melt‐synthesized copolyamides were random. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5118–5129 相似文献
11.
Qi Sheng Liu Lian Dong Liu Jing Min Shi 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):m58-m60
In the title centrosymmetric binuclear complex, [Cd2(C17H11N3O)4(H2O)2](ClO4)4, the CdII ion assumes a distorted octahedral geometry. There are π–π stacking interactions between the pyridine and 1,10‐phenanthroline ring systems of adjacent ligands at the same CdII centre. Intermolecular hydrogen bonds between the coordinated aqua ligand and the O atom of a keto group connect adjacent complex cations into extended chains. Hydrogen bonds also exist between the complex cations and the perchlorate anions. Compared with the fluorescence spectrum of the organic ligand, the complex displays strong fluorescent emission and an ipsochromic shift of the emission peaks, which may be attributed to the structural character. 相似文献
12.
Augusto Rivera James Guevara‐Pulido John Sadat‐Bernal Jaime Ríos‐Motta Guillermo Zaragoza 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(9):o435-o437
The title compound, 1,5:3,7‐dimethano‐1,3,5,7‐benzotetrazonine–hydroquinone (2/1), 2C11H14N4·C6H6O2, crystallizes with the hydroquinone molecule located on a center of inversion. In contrast to other hydroquinone–adamanzane adducts, which form extended hydrogen‐bonded networks, in the present case, one hydroquinone molecule is linked to two 1,5:3,7‐dimethano‐1,3,5,7‐benzotetrazonine molecules, forming a 2:1 cluster through O—H...N hydrogen bonds. 相似文献
13.
smund Kaupang Carl Henrik Grbitz Tore Bonge‐Hansen 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(7):778-780
The organic acid–base complex 1,1,3,3‐tetramethylguanidinium 4‐methylbenzenesulfonate, C5H14N3+·C7H7O3S−, was obtained from the corresponding 1,1,3,3‐tetramethylguanidinium 4‐methylbenzenesulfinate complex, C5H14N3+·C7H7O2S−, by solid‐state oxidation in air. Comparison of the two crystal structures reveals similar packing arrangements in the monoclinic space group P21/c, with centrosymmetric 2:2 tetramers being connected by four strong N—H...O=S hydrogen bonds between the imine N atoms of two 1,1,3,3‐tetramethylguanidinium bases and the O atoms of two acid molecules. 相似文献
14.
Patrizia Rossi Paola Paoli Laura Chelazzi Luca Conti Andrea Bencini 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(2):87-96
Metoprolol {systematic name: (RS)‐1‐isopropylamino‐3‐[4‐(2‐methoxyethyl)phenoxy]propan‐2‐ol}, C15H25NO3, is a cardioselective β1‐adrenergic blocking agent that shares part of its molecular skeleton with a large number of other β‐blockers. Results from its solid‐state characterization by single‐crystal and variable‐temperature powder X‐ray diffraction and differential scanning calorimetry are presented. Its molecular and crystal arrangements have been further investigated by molecular modelling, by a Cambridge Structural Database (CSD) survey and by Hirshfeld surface analysis. In the crystal, the side arm bearing the isopropyl group, which is common to other β‐blockers, adopts an all‐trans conformation, which is the most stable arrangement from modelling data. The crystal packing of metoprolol is dominated by an O—H…N/N…H—O pair of hydrogen bonds (as also confirmed by a Hirshfeld surface analysis), which gives rise to chains containing alternating R and S metoprolol molecules extending along the b axis, supplemented by a weaker O…H—N/N—H…O pair of interactions. In addition, within the same stack of molecules, a C—H…O contact, partially oriented along the b and c axes, links homochiral molecules. Amongst the solid‐state structures of molecules structurally related to metoprolol deposited in the CSD, the β‐blocker drug betaxolol shows the closest analogy in terms of three‐dimensional arrangement and interactions. Notwithstanding their close similarity, the crystal lattices of the two drugs respond differently on increasing temperature: metoprolol expands anisotropically, while for betaxolol, an isotropic thermal expansion is observed. 相似文献
15.
Alvaro S. de Sousa Zanele Hlam Manuel A. Fernandes Helder M. Marques 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(4):o229-o232
The crystal structure of the title compound, C8H17NO2, consists of (R,R) and (S,S) enantiomeric pairs packed in adjacent double layers which are characterized by centrosymmetric hydrogen‐bonded dimers, generated via N—H...O and O—H...O interactions, respectively. Intermolecular interactions, related to acceptor and donor molecule chirality, link the achiral double layers into tubular columns, which consist of a staggered hydrophilic inner core surrounded by a hydrophobic cycloalkyl outer surface and extend in the [011] direction. 相似文献
16.
Collective Synthesis of 4‐Hydroxy‐2‐pyridone Alkaloids and Their Antiproliferation Activities
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Feiqing Ding Min Li Leow Dr. Jimei Ma Ronny William Hongze Liao Prof. Dr. Xue‐Wei Liu 《化学:亚洲杂志》2014,9(9):2548-2554
A collective synthesis of 4‐hydroxy‐2‐pyridone alkaloids—specifically, pretenellin B, prebassianin B, farinosone A, militarione D, pyridovericin, and torrubiellone C—has been achieved. Key steps include using a strategic convergent method to synthesize the densely substituted pyridone key intermediate by Suzuki–Miyaura cross‐coupling reaction, a divergent synthesis approach of target molecules by aldol condensation of pyridone intermediate with homologous aldehydes, and an iterative synthesis of homologous aldehydes with all‐trans‐polyene backbones. Interestingly, among the six tumor cell lines investigated, torrubiellone C was found to induce potent and apoptotic inhibitory activities on Jurkat T cells with IC50 values of 7.05 μM . Hence, this approach could potentially contribute to the synthesis of bioactive small‐molecule libraries as well as drug discovery. 相似文献
17.
Daisuke Sawai Kazuyo Takahashi Toshiyuki Imamura Koh Nakamura Tetsuo Kanamoto Suong‐Hyu Hyon 《Journal of Polymer Science.Polymer Physics》2002,40(1):95-104
Melt‐crystallized, low molecular weight poly(L ‐lactic acid) (PLLA) consisting of α crystals was uniaxially drawn by solid‐state extrusion at an extrusion temperature (Text) of 130–170 °C. A series of extrusion‐drawn samples were prepared at an optimum Text value of 170 °C, slightly below the melting temperature (Tm) of α crystals (~180 °C). The drawn products were characterized by deformation flow profiles, differential scanning calorimetry (DSC) melting thermograms, wide‐angle X‐ray scattering (WAXD), and small‐angle X‐ray scattering as a function of the extrusion draw ratio (EDR). The deformation mode in the solid‐state extrusion of semicrystalline PLLA was more variable and complex than that in the extensional deformation expected in tensile drawing, which generally gave a mixture of α and β crystals. The deformation profile was extensional at a low EDR and transformed to a parabolic shear pattern at a higher EDR. At a given EDR, the central portion of an extrudate showed extensional deformation and the shear component became progressively more significant, moving from the center to the surface region. The WAXD intensities of the (0010)α and (003)β reflections on the meridian as well as the DSC melting thermograms showed that the crystal transformation from the initial α form to the oriented β form proceeded rapidly with increasing EDR at an EDR greater than 4. Furthermore, WAXD showed that the crystal transformation proceeded slightly more rapidly at the sheath region than at the core region. This fact, combined with the deformation profiles (shear at the sheath and extensional at the core), indicated that the crystal transformation was promoted by shear deformation under a high pressure rather than by extensional deformation. Thus, a highly oriented rod consisting of only β crystals was obtained by solid‐state extrusion of melt‐crystallized, low molecular weight PLLA slightly below Tm. The structure and properties of the α‐ and β‐form crystals were also studied. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 95–104, 2002 相似文献
18.
Akira Furukawa Yukio Imanishi Masao Tanihara 《Journal of polymer science. Part A, Polymer chemistry》2003,41(21):3227-3242
We designed a new type of styrenyl compound applicable to conventional photopolymerization systems, aiming at the production of polymers with improved mechanical properties, resistance to chemicals, and elevated glass‐transition temperatures (Tg's). A series of styrenyl monomers bearing 2,5‐dithio‐1,3,4‐thiadiazole groups were prepared, and their reactivity was studied in solid‐state photopolymerization initiated by 2‐(4′‐methoxystyryl)‐4,6‐bis(trichloromethyl)‐1,3,5‐triazine. These monomers exhibited much higher polymerization rates than usual, and the final conversion nearly reached completion, despite the relatively high Tg of the solid‐state photopolymerization system. Even at temperatures below Tg, the polymerization proceeded without a ceiling phenomenon. These features were explained by intermolecular interactions between the monomers that induced monomer alignments effective for solid‐state polymerization, large excess free volumes arising from rotation around the methylthio groups, and intramatrix radical migration leading to encounters with the remaining monomers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3227–3242, 2003 相似文献
19.
《Magnetic resonance in chemistry : MRC》2003,41(12):1026-1029
Solid‐state cross‐polarization magic angle spinning 13C, 77Se and 15N NMR spectra were recorded for 1,3‐imidazolidine‐2‐selenone, its N‐substituted derivatives and some related compounds. The spinning sideband manifold intensities were used to obtain principal values of 13C and 77Se chemical shift tensors. Large selenium chemical shift anisotropies were observed for these selenones. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
20.
Md. Ashraf Ali Shuji Noguchi Miteki Watanabe Yasunori Iwao Shigeru Itai 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(10):743-747
7‐Ethyl‐10‐hydroxycamptothecin [systematic name: (4S)‐4,11‐diethyl‐4,9‐dihydroxy‐1H‐pyrano[3′,4′:6,7]indolizino[1,2‐b]quinoline‐3,14(4H,12H)‐dione, SN‐38] is an antitumour drug which exerts activity through the inhibition of topoisomerase I. The crystal structure of SN‐38 as the monohydrate, C22H20N2O5·H2O, reveals that it is a monoclinic crystal, with one SN‐38 molecule and one water molecule in the asymmetric unit. When the crystal is heated to 473 K, approximately 30% of SN‐38 is hydrolyzed at its lactone ring, resulting in the formation of the inactive carboxylate form. The molecular arrangement around the water molecule and the lactone ring of SN‐38 in the crystal structure suggests that SN‐38 is hydrolyzed by the water molecule at (x, y, z) nucleophilically attacking the carbonyl C atom of the lactone ring at (x − 1, y, z − 1). Hydrogen bonding around the water molecules and the lactone ring appears to promote this hydrolysis reaction: two carbonyl O atoms, which are hydrogen bonded as hydrogen‐bond acceptors to the water molecule at (x, y, z), might enhance the nucleophilicity of this water molecule, while the water molecule at (−x, y + , −z), which is hydrogen bonded as a hydrogen‐bond donor to the carbonyl O atom at (x − 1, y, z − 1), might enhance the electrophilicity of the carbonyl C atom. 相似文献