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991.
The miscibility and thermal properties of poly(N‐phenyl‐2‐hydroxytrimethylene amine)/poly(N‐vinyl pyrrolidone) (PHA/PVP) blends were examined by using differential scanning calorimetry (DSC), high‐resolution solid‐state nuclear magnetic resonance (NMR) techniques, and thermogravimetric analysis (TGA). It was found that PHA is miscible with PVP, as shown by the existence of a single composition‐dependent glass transition temperature (Tg) in the whole composition range. The DSC results, together with the 13C crosspolarization (CP)/magic angle spinning (MAS)/high‐power dipolar decoupling (DD) spectra of the blends, revealed that there exist rather strong intermolecular interactions between PHA and PVP. The increase in hydrogen bonding and in Tg of the blends was found to broaden the line width of CH—OH carbon resonance of PHA. The measurement of the relaxation time showed that the PHA/PVP blends are homogeneous at least on the scale of 1–2 nm. The proton spin‐lattice relaxation in both the laboratory frame and the rotating frame were studied as a function of the blend composition, and it was found that blending did not appreciably affect the spectral densities of motion (sub‐Tg relaxation) in the mid‐MHz and mid‐KHz frequency ranges. Thermogravimetric analysis showed that PHA has rather good thermal stability, and the thermal stability of the blend can be further improved with increasing PVP content. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 237–245, 1999 相似文献
992.
Karla-Alejandra Lpez-Gastlum Enrique F. Velzquez-Contreras Juventino J. García Marcos Flores-Alamo Gerardo Aguirre Daniel Chvez-Velasco Jayanthi Narayanan Fernando Rocha-Alonzo 《Molecules (Basel, Switzerland)》2021,26(23)
Two new glycine-Schiff base copper(II) complexes were synthesized. Single crystal X-ray diffraction (SCXRD) allowed us to establish the structure of both complexes in the solid state. The glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-nitroacetophenone showed a mononuclear hydrated structure, in which the Schiff base acted as a tridentate ligand, and the glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-methylacetophenone showed a less common tetranuclear anhydrous metallocyclic structure, in which the Schiff base acted as a tetradentate ligand. In both compounds, copper(II) had a tetracoordinated square planar geometry. The results of vibrational, electronic, and paramagnetic spectroscopies, as well as thermal analysis, were consistent with the crystal structures. Both complexes were evaluated as catalysts in the olefin cyclopropanation by carbene transference, and both led to very high diastereoselectivity (greater than 98%). 相似文献
993.
Manisha Das Dipmalya Basak Prof. Dr. Zdeněk Trávníček Dr. Ján Vančo Prof. Dr. Debashis Ray 《化学:亚洲杂志》2019,14(21):3898-3914
Simultaneous incorporation of both CoII and CoIII ions within a new thioether S‐bearing phenol‐based ligand system, H3L (2,6‐bis‐[{2‐(2‐hydroxyethylthio)ethylimino}methyl]‐4‐methylphenol) formed [Co5] aggregates [CoIICoIII4L2(μ‐OH)2(μ1,3‐O2CCH3)2](ClO4)4?H2O ( 1 ) and [CoIICoIII4L2(μ‐OH)2(μ1,3‐O2CC2H5)2](ClO4)4?H2O ( 2 ). The magnetic studies revealed axial zero‐field splitting (ZFS) parameter, D/hc=?23.6 and ?24.3 cm?1, and E/D=0.03 and 0.00, respectively for 1 and 2 . Dynamic magnetic data confirmed the complexes as SIMs with Ueff/kB=30 K ( 1 ) and 33 K ( 2 ), and τ0=9.1×10?8 s ( 1 ), and 4.3×10?8 s ( 2 ). The larger atomic radius of S compared to N gave rise to less variation in the distortion of tetrahedral geometry around central CoII centers, thus affecting the D and Ueff/kB values. Theoretical studies also support the experimental findings and reveal the origin of the anisotropy parameters. In solutions, both 1 and 2 which produce {CoIII2(μ‐L)} units, display solvent‐dependent catechol oxidation behavior toward 3,5‐di‐tert‐butylcatechol in air. The presence of an adjacent CoIII ion tends to assist the electron transfer from the substrate to the metal ion center, enhancing the catalytic oxidation rate. 相似文献
994.
Kyosuke Morimoto Thien Phuc Le Sudipta Kumar Manna I. N. Chaithanya Kiran Shinji Tanaka Masato Kitamura 《化学:亚洲杂志》2019,14(19):3221-3221
995.
Anna Vrblov Juraj ernk Larry R. Falvello Milagros Toms 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(4):433-442
Reactions of Co(OH)2 with the Schiff base bis(2‐hydroxy‐3‐methoxybenzylidene)ethylenediamine, denoted H2(o‐van‐en), under different conditions yielded the previously reported complex aqua[bis(3‐methoxy‐2‐oxidobenzylidene)ethylenediamine]cobalt(II), [Co(C18H18N2O4)(H2O)], 1 , under anaerobic conditions and two polymorphs of [μ‐bis(3‐methoxy‐2‐oxidobenzylidene)ethylenediamine]bis{[bis(3‐methoxy‐2‐oxidobenzylidene)ethylenediamine]cobalt(III)} acetonitrile tetrasolvate, [Co2(C18H18N2O4)3]·4CH3CN, i.e. monoclinic 2 and triclinic 3 , in the presence of air. Both novel polymorphs were chemically and spectroscopically characterized. Their crystal structures are built up of centrosymmetric dinuclear [Co2(o‐van‐en)3] complex molecules, in which each CoIII atom is coordinated by one tetradentate dianionic o‐van‐en ligand in an uncommon bent fashion. The pseudo‐octahedral coordination of the CoIII atom is completed by one phenolate O and one amidic N atom of the same arm of the bridging o‐van‐en ligand. In addition, the asymmetric units of both polymorphs contain two acetonitrile solvent molecules. The polymorphs differ in the packing orders of the dinuclear [Co2(o‐van‐en)3] complex molecules, i.e. alternating ABABAB in 2 and AAA in 3 . In addition, differences in the conformations, the positions of the acetonitrile solvent molecules and the pattern of intermolecular interactions were observed. Hirshfeld surface analysis permits a qualitative inspection of the differences in the intermolecular space in the two polymorphs. A knowledge‐based study employing Full Interaction Maps was used to elucidate possible reasons for the polymorphism. 相似文献
996.
Ajeet Kumar Sharma Parul Bansal Gaurav Kumar Nim Prasenjit Kar 《Particle & Particle Systems Characterization》2019,36(12)
This work reports the first synthesis of MAPbBr3 perovskite nanocrystals (PNCs) using amino acids as the ligand with excellent optical properties. A variety of amino acids are used to optimize the luminescence properties. A mechanochemical approach has taken lead over conventional colloidal chemistry during synthesis. All morphological and optical studies are performed to characterize the synthesized perovskite nanoparticles. Later, stability studies are investigated through thermogravimetric analysis, temperature‐dependent photoluminescence, time‐dependent X‐ray diffraction, as well as X‐ray photoelectron spectroscopy. In an application, interestingly, these perovskites show high luminescence upon scratching on flexible conducting plates and on plain paper surface. These results suggest that the amino acid–ligated perovskite nanocrystals can be potential materials for optoelectronic application including light‐emitting diodes and imaging. 相似文献
997.
开发高效的催化剂用于催化还原CO2转化为甲酸和它的盐类已经成为研究的热点,是因为将CO2转化为C1产物不仅可以解决CO2的含量升高带来的环境问题,还可以解决化石能源燃烧日趋严重的问题。贵金属配合物催化CO2转化为甲酸和甲酸盐类是目前这类反应最有效的方式,尤其是Ru、Ir和Rh等贵金属。我们之前的研究结果表明Ir(Ⅲ), Ru(Ⅱ)类配合物催化还原CO2转化为甲酸盐的活性是由配合物Ru―H键的成键性质决定的。它们能高活性的催化CO2是由于它们都含有同一种特点的Ru―H键,是由Ru的sd2杂化轨道和H的1s轨道杂化而成的,而且这一特点可以被活性氢的对位配体显著影响。鉴于硼基配体具有强的对位效应,我们基于高活性的均相催化剂Ru(PNP)(CO)H2 (PNP = 2, 6-二(二叔丁基磷甲基)-吡啶)设计了Ru-PNP-HBcat和Ru-PNP-HBpin,并计算了二者催化还原CO2的活性。Bcat和Bpin配体是实验上常用的硼基配体。我们的计算结果表明Ru-PNP-HBcat和Ru-PNP-HBpin有比Ru-PNP-H2更长的Ru―H键、亲核性更强的活性氢,其Ru―H键中的Ru原子的d轨道杂化成分的贡献也比Ru-PNP-H2的更少。相应地Ru-PNP-HBcat和Ru-PNP-HBpin活化CO2的能垒比Ru-PNP-H2低。而且Ru-PNP-H2、Ru-PNP-HBcat和Ru-PNP-HBpin催化CO2转化为甲酸盐的能垒分别为76.2、67.8、54.4 kJ∙mol-1,表明Ru-PNP-HBpin具有最高的催化活性。因此,钌配合物催化还原CO2的活性可由硼基配体强的对位效应和Ru―H键的成键性质来调控。 相似文献
998.
1901年Ullmann报道了一个形成sp2C-C键的偶联反应,1903年报道了苯胺的N-芳基化反应,1905年又报道了苯酚的O-芳基化的缩合反应。这些经典的反应进入催化领域且范围又有扩展,但由于反应条件苛刻等缺点,也限制了反应的应用。20世纪末,在多位科学家的努力下,发现具有一定结构的化合物--配体,对于铜催化的Ullmann缩合反应(或交叉偶联反应)具有配体加速催化反应(LAC)的效果,于是引发了对这一反应的研究热潮。本文对于各种配体的选用,特别是草酰二胺类,对于无机碱,特别是有机离子性碱的选用以及铜源、配体的负载化、溶剂的考量和绿色化等方面进行了较为详细的讨论。鉴于在2004年已有单篇论文提出了Ullmann反应的复兴,Beletskaya则提出了精辟的问题:这就是复兴吗?在金属催化的交叉偶联反应中,铜催化是否已成为钯催化的有力竞争者?Beletskaya在历数了铜催化的优点之后,也深刻地列出了铜催化的五大不足之处。经过了十余年众多化学家的成功发展,本文对此给出了明确的回答。 相似文献
999.
WANG Shihui LI Haiyan WANG Yue GAO Yang YU Shanshan ZHAO Qianqian JIN Xiangqun LU Haibin 《高等学校化学研究》2018,34(2):221-228
In this paper, we synthesized a series of proteolysis targeting chimeras(PROTACs) using VHL E3 ligase ligands for BRD4 protein degradation. One of the most promising compound 19g exhibited robust potency of BRD4 inhibition with IC50 value of (18.6±1.3) nmol/L, respectively. Furthermore, compound 19g potently inhibited cell proliferation in BRD4-sensitive cell lines RS4;11 with IC50 value of (34.2±4.3) nmol/L and capable of inducing degradation of BRD4 protein at 0.4—0.6 µmol/L in the RS4;11 leukemia cells. These data show that compound 19g is a highly potent and efficacious BRD4 degrader. 相似文献
1000.
A three-dimentinal metal organic framework[Co2(L)Cl(DMF)2(H2O)](DMF)3(H2O)3 based on the nanometresized ligand 4,4',4"-[1,3,5-benzenetriyltris(carbonylimino)]trisbenzoic acid was synthesized, and characterized by means of single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetry analysis and magnetism. This obtained structure can be considered to be constructed from 2D layer, which displays the topology of hbc based on Co2(COO)3 secondary building unit, and further to be linked into a 3D supramolecular architecture by N-H…O hydrogen bonds. The magnetism of the complex was carried out, which shows ferromagnetic exchange interactions. 相似文献