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81.
The 1H and 87Rb spin-lattice relaxation and spin-spin relaxation times in superionic Rb3H(SeO4)2 single crystals grown by the slow evaporation method were measured over the temperature range 160-450 K. The temperature dependencies of the 1H T1, T1ρ, and T2 are measured. In the ferroelastic phase, T1 differs from T1ρ, which is in turn different from T2, although these three relaxation times converge to similar values near 410 K. This transition seems to occur at temperature which is about 40 K lower than the superionic transition temperature. The observation of liquid-like values of the 1H T1, T1ρ, and T2 in the high temperature is compatible with the phase being superionic, indicating that the destruction and reconstruction of hydrogen bonds does indeed occur at high temperature. In addition, the 87Rb T1 and T2 values at high temperature were similar (on the order of milliseconds), a trend that was also observed for 1H T1 and T2. This behavior is expected for most hopping-type ionic conductors, and could be attributed to interactions between the mobile ions and the neighboring group ions within the crystal. The motion giving rise to this liquid-like behavior is related to the superionic motion. 相似文献
82.
Chun-Kiu Kwok Thomas C. W. Mak 《Journal of inclusion phenomena and macrocyclic chemistry》1988,6(5):461-471
N,Nk86/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-DicyclohexylpiperazineN,Nk86/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-dioxide octahydrate, C16H46N2O10,M
r=426.55, monoclinic, space groupC2/m (No. 12),a=12.961(4),b=11.533(4),c=7.907(1) Å, k86/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">=98.37(2)o,V=1169.3(6) Å3,Z=2. The structure was solved by the direct method and refined toR=0.045 for 1192 observed MoK
k86/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> reflections. TheN,Nk86/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-dioxide molecule occupies a site of symmetry 2/m. The piperazine ring takes the chair form with the two N–O bonds oriented axially in atrans configuration. Hydrogen bonding between the water molecules, as well as between theN-oxide groups and water molecules, gives rise to a puckered layer composed of edge-sharing four-membered, five-membered, six-membered, and eight-membered rings. Adjacent layers are cross-linked by theN,Nk86/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-dicyclohexylpiperazine moieties lying between them, thereby generating a k86/xxlarge8216.gif" alt="lsquo" align="BASELINE" BORDER="0">sandwichk86/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> structure consolidated by covalent and hydrogen bonding.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82062 (8 pages). 相似文献
83.
L. V. Pankratov V. I. Nevodchikov L. N. Zakharov G. K. Fukin S. Ya. Khorshev M. N. Bochkarev Yu. T. Struchkov 《Russian Chemical Bulletin》1994,43(2):295-298
Dehydrogenation of pentafluorophenylgermane in the presence of catalytic amounts of a Wilkinson complex, certain RhI
ortho-benzosemiquinolate complexes, or (Ph3P)4Pt leads to tetrahydrodigermane, C6F5H2GeGeH2C6F5. X-ray analysis has confirmed thetrans-arrangement of the C6F5-cycles at the Ge atoms. The Ge-Ge bond length is 2.394(1) Å. The doublet pattern of the band due to the Ge-H bonds (v 2090 and 2104 cm–1) in the IR spectrum is probably associated with nonequivalence of the hydrogen atoms in the molecule.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 315–318, February, 1994. 相似文献
84.
《Arabian Journal of Chemistry》2022,15(4):103712
Although recent decades have witnessed the synthesis of 1,3,4-thiadiazoles via phosphorus POCl3-promoted cyclization reaction, simultaneous access to 2-amino-1,3,4-thiadiazole and 2-amino-1,3,4-oxadiazole analogs remains unexpected and elusive. Herein, a detailed regiocontrolled synthesis of 2-amino-1,3,4-thiadiazoles in good to high yields with good regioselectivities from readily available thiosemicarbazides using POCl3 was disclosed. Meantime, to establish a comprehensive structure–activity relationship, 2-amino-1,3,4-oxadiazole derivatives as single regioisomers were prepared via EDCI·HCl-triggered cyclization of the thiosemicarbazide intermediates. The in vitro anti-influenza assays proved that the selected compounds with the pyrazine/pyridine ring exhibited certain inhibitory activities against influenza A virus strains A/HK/68 (H3N2) and A/PR/8/34 (H1N1) in MDCK cells. Among them, N-(adamantan-1-yl)-5-(5-(azepan-1-yl)pyrazin-2-yl)-1,3,4-thiadiazol-2-amine (4j) was the most active compound, and exhibited favorable activity with EC50 values of 3.5 μM and 7.5 μM, respectively. In addition, the molecular docking results explained the reason why compound 4j had dual inhibitory activity and revealed the reasonable binding mode of this compound with the M2-S31N and M2-WT ion channels. This compound had the potential to be further developed as an anti-influenza drug. 相似文献
85.
Indirect reduction of 1-phenylethylbromide (I) and 1-(4-isobutylphenyl)ethylchloride (II) in a carbon dioxide atmosphere containing tris(2,2k635k3g15/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-bipyridyl)nickel tetrafluoroborate (BPN) is studied. In the reactions the BPN complex exhibits properties of a one-electron mediator and catalyzes radical generation from aryl halides, which mostly undergo dimerization. Electroreduction of I and II in the presence of k635k3g15/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin and BPN yields biaryls with a low enanthioselectivity (k635k3g15/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0">1.5%), which may indicate generation of a small amount of inclusion complexes and dimerization of intermediate radicals in the hydrophobic cavity of k635k3g15/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin. 相似文献
86.
《Arabian Journal of Chemistry》2022,15(8):104019
Plant bacteria and viruses have a huge negative impact on food crops in the world. Therefore, it is important to create new and efficient green pesticides. In this paper, a series of myricetin derivatives containing quinazolinone sulfide were introduced. Good antibacterial and antiviral activities of the drug molecules 2-((3-((5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-chromen-3-yl)oxy)propyl)thio)-6-fluoro-3-phenylquinazolin-4(3H)-one (T5) and 2-((4-((5,7-dimethoxy-4-oxo-2-(3,4,5-trimethoxyphenyl)-4H-chromen-3-yl)oxy)butyl)thio)-6-methyl-3-phenylquinazolin-4(3H)-one (T15) respectively were found by biological activity screening. The value of dissociation constant (Kd) of compound T15 to TMV CP was 0.024 ± 0.006 μM, determined by Microscale thermophoresis (MST), which was far less than the value of 8.491 ± 2.027 μM of commercial drug ningnanmycin (NNM). The interaction between compound T15 and TMV CP was further verified by molecular docking. Compound T15 formed strong hydrogen bonds with residues SER:49 and SER:15 (1.92 Å, 2.20 Å, respectively), which were superior to the traditional hydrogen bonds formed by NNM with residue SER:215 (3.64 Å). In addition, the effects of compound T15 on the contents of chlorophyll and peroxidase (POD) in tobacco were studied, and the results indicated that compound T15 could enhance the disease resistance of tobacco plants to a certain extent. 相似文献
87.
《Arabian Journal of Chemistry》2022,15(7):103933
In this study, a fingerprint-activity relationship modeling between chemical fingerprints and antirheumatic activity was established, and multivariate statistical analysis was used to evaluate the quality of Taxilli Herba (TH) from different hosts. Characteristic fingerprints of 20 batches of TH samples were generated by high-performance liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (HPLC-Triple TOF-MS/MS), and the similarity analysis was calculated based on thirteen common characteristic peaks by hierarchical clustering analysis (HCA). Subsequently, nine efficacy markers were discovered by combining fingerprints and antirheumatic activity through grey correlation analysis (GCA) and bivariate correlation analysis (BCA). Meanwhile, the content of 5 constituents in 9 markers was determined by high-performance liquid chromatography coupled with triple quadrupole-linear ion trap tandem mass spectrometry (HPLC-QTRAP-MS/MS). The comprehensive quality of TH was assessed using multivariate statistical analysis, including principal components analysis (PCA) and technique for order preference by similarity to ideal solution (TOPSIS). The results showed that a high dose of TH extract could markedly ameliorate arthritis damage compared to other doses, with flavonoids playing an important role in the antirheumatic activity. The comprehensive quality of samples from Morus alba L. (SS) was superior to those from Liquidambar formosana Hance (FXS). The present study will demonstrate the markers associated with efficacy, and provide an applicable strategy for more comprehensive quality control and evaluation of TH. 相似文献
88.
A. L. Rusanov G. S. Matvelashvili G. V. Kazakova M. L. Keshtov A. K. Mikitaev 《Russian Chemical Bulletin》1996,45(3):633-636
Synthesis of 4,4k64x432/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-bis(4-aminophenoxy)benzophenone was performed starting from chloral. Various polyimides were obtained by reactions of 4,4 k64x432/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-bis(4-aminophenoxy)benzophenone with aromatic tetracarboxylic acid dianhydrides. Some of the polyimides obtained are crystalline compounds.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 673–676, March, 1996. 相似文献
89.
The geometry of the linear molecule HBO, has been investigated within the restricted Hartree-Fock LCAO-MO-SCF approximation. The calculated bond lengths for the near Hartree-Fock calculation were R(H-B)=2.1913 bohr, R(B-O)=2.2284 bohr. Several one electron properties have been calculated for the minimum energy configuration. 相似文献
90.
Ali Taha Viktor Gutmann Wolfgang Linert 《Monatshefte für Chemie / Chemical Monthly》1991,122(5):327-339
Summary The solvatochromic and thermochromic behaviour of a series of mixed Ni(II) complexes with unsubstituted and substituted k872m356u15h5/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-diketones and diamines in the solvents 1,2-dichloroethane (DCE), acetonitrile (An), acetone (AC),n-butanol (n-BuOH), formamide (FA), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine (PY) has been studied and characterized on the basis of electronic spectra. Spectrophotometric methods have been used to evaluate equilibrium constants and their enthalpic and entropic terms for the formation of Ni(k872m356u15h5/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-dik)(diam)L
+ and Ni(k872m356u15h5/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-dik)(diam)L
2
+
. Increasing donor strength of the donor-solvents (L) and (or) increasing electronwithdrawing parameters of the substituents at the k872m356u15h5/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-diketone and the diamine ligands lead to increasing formation constants, paralleled by relative increase in the stability of the five-coordinated species Ni(k872m356u15h5/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-dik)(diam)L
+. The results are discussed in terms of the extended donor-acceptor concept.On leave of absence from the Faculty of Education, Ain Schams University, Roxy, Cairo, Egypt 相似文献