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91.
Theoretical investigations on the insertion reaction mechanisms of three- membered-ring silylenoid H2 Si Li F with GeH 3R(R = F, OH, NH2) have been systematically carried out by combined density functional theory(DFT) and ab initio quantum chemical calculations. The geometries of all stationary points for these reactions were optimized using the B3 LYP method and then the QCISD method was used to calculate the single-point energies. The calculated results indicate that, there are one precursor complex(Q), one transition state(TS), and one intermediate(IM) which connect the reactants and the products along the potential energy surface. The insertion reactions of three-membered-ring silylenoid with Ge H3 R proceed in a concerted manner, forming H2RSi-Ge H3 and Li F. The calculated potential energy barriers of the three reactions are 29.17, 30.90, and 54.07 k J/mol, and the reaction energies for the three reactions are –127.05, –116.91, and –103.31 k J/mol, respectively. The insertion reactions in solvents are similar to those in vacuum. Under the same situation, the insertion reactions should occur easily in the following order: GeH 3-F GeH 3-OH GeH 3-NH2. The elucidations of the mechanism of these insertion reactions provided a new mode of silicon-germanium bond formation. 相似文献
92.
Partial substitution of cations and anions in perovskite-type materials is a powerful way to tune the desired properties. The systematic variation of the cations size, the partial exchange of O2− for N3− and their effect on the size of the optical band gap and the thermal stability was investigated here. The anionic substitution resulted in the formation of the orthorhombic perovskite-type oxynitrides Mg0.25Ca0.65Y0.1Ti(O,N)3, Ca1-xYxZr(O,N)3, and Sr1–xLaxZr(O,N)3. A two-step synthesis protocol was applied: i) (nano-crystalline) oxide precursors were synthesized by a Pechini method followed by ii) ammonolysis in flowing NH3 at T = 773 K (Ti) and T = 1273 K (Zr), respectively. High-temperature synthesis of such oxide precursors by solid–state reaction generally resulted in phase separation of the different A-site cations. Changes of the crystal structures were investigated by Rietveld refinements of the powder XRD data, thermal stability by DSC/TG measurements in oxygen atmosphere, oxygen and nitrogen contents by O/N analysis using hot gas extraction technique, and optical band gaps by photoluminescence spectroscopy. By moving from Mg0.25Ca0.65Y0.1Ti(O,N)3 via Ca1–xYxZr(O,N)3 to Sr1–xLaxZr(O,N)3, the degree of tilting of the octahedral network is reduced, as observed by an increase in the B–X–B angles caused by the simultaneously increasing effective ionic radius of the A-site cation(s). In general, increasing substitution levels on the A-site (Y3+ and La3+) are accompanied by an enhanced replacement of O2− by N3−. In all three systems, this anionic substitution resulted in a reduction of the optical band gap by approximately 1 eV (Ti) and up to 2.1 eV (Zr) compared to the respective oxides. For Mg0.25Ca0.65Y0.1Ti(O,N)3 an optical band gap of 2.2 eV was observed, appropriate for a solar water splitting photocatalyst. The Zr-based oxynitrides required a by a factor of 2 higher nitrogen contents to significantly reduce the optical band gap and the measured values of 2.9 eV–3.2 eV are larger compared to the Ti-based oxynitride. Bulk thermal stability was revealed up to T = 881 K. In general, the thermal stability decreased with increasing substitution levels due to an increasing deviation from the ideal anionic composition as demonstrated by O/N analysis. 相似文献
93.
A new compound, [H2N(CH3)2]2[Zn(btec)].H2O(1, H4 btec = 1,2,4,5-benzenetetracarboxylic acid) has been solvothermally synthesized and structurally characterized by singlecrystal X-ray diffraction. The crystal structure is of monoclinic, space group P21/c with a = 9.5741(3), b = 14.5044(4), c = 13.7329(5) , β = 100.582(4)°, V = 1874.61(10) 3, C14H20N2O9 Zn, Mr = 425.7, Z = 4, Dc = 1.387 g/cm3, μ = 1.349 mm-1, F(000) = 776, R = 0.0560 and w R = 0.1684 for 2834 observed reflections(I 2σ(I)). Compound 1 based on μ4-btec and tetrahedral building unit features a three-dimensional(3D) anionic framework with mixed connected nou topology. The luminescent property and thermogravimetric analysis of compound 1 are investigated. 相似文献
94.
Daniel Xu Andreas Tairych Iain A. Anderson 《Journal of Polymer Science.Polymer Physics》2016,54(4):465-472
Practice makes perfect to some extent. Research has shown that musicians who practice the piano for long periods of time can suffer a range of hand problems from loss of control to diminished speed. Now imagine a rubber keyboard that is springy, soft, and elastic. This is the new type of input device that dielectric elastomers (DE) can create. However their usage in large sensing systems is limited by a scalability challenge. Each DE sensor is married to a pair of connection cables and electronics, adding to the complexity of the background overheads. A new efficient multi‐frequency method is presented that is capable of detecting internal pressure changes from a difference in the DE's capacitance without the need for any additional wires or connections. This effectively segments the DE into smaller sections, achieving information from a single sensor equivalent to multiple sensors. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 465–472 相似文献
95.
96.
在DMF/H2O/CH3OH的混合体系中,反应温度为170℃,Mn SO4·4H2O盐溶液在p H=5和7的条件下,加热72小时,最终得到了结构不同的硫酸锰骨架[Mn2(SO4)3]·(H3O)2(1)和[Mn3(SO4)2(OH)2(H2O)2](2)。化合物结构通过单晶X-射线和红外光谱所表征,相应的晶胞参数:化合物1,立方晶系,空间群:P213,a=10.2009(12),V=1061.49(37)3,Goo F=1.158,Flack parameter 0.02(2),R1=0.0186(I2sigma);化合物2,四方晶系,空间群:Pbcm,a=7.3214(15),b=9.984(2),c=13.291(3),V=971.5(4)3,Goo F=1.063,R1=0.0227(I2sigma);单晶X射线分析显示化合物1是一个三维单手性硫酸锰骨架,化合物2是一个非手性羟基硫酸锰骨架。实验结果说明,p H值对硫酸锰骨架的改变起重要作用。 相似文献
97.
Specific Design of Titanium(IV) Phenolato Chelates Yields Stable and Accessible,Effective and Selective Anticancer Agents 下载免费PDF全文
Sigalit Meker Dr. Ori Braitbard Dr. Matthew D. Hall Prof. Jacob Hochman Prof. Edit Y. Tshuva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9986-9995
Octahedral titanium(IV) complexes of phenolato hexadentate ligands were developed and showed very high stability for days in water solutions. In vitro cytotoxicity studies showed that, whereas tetrakis(phenolato) systems are generally of low activity presumably due to inaccessibility, smaller bis(phenolato)bis(alkoxo) complexes feature high anticancer activity and accessibility even without formulations, also toward a cisplatin‐resistant cell line. An all‐aliphatic control complex was unstable and inactive. A leading phenolato complex also revealed: 1) high durability in fully aqueous solutions; accordingly, negligible loss of activity after preincubation for three days in medium or in serum; 2) maximal cellular accumulation and induction of apoptosis following 24–48 h of administration; 3) reduced impact on noncancerous fibroblast cells; 4) in vivo efficacy toward lymphoma cells in murine model; 5) high activity in NCI‐60 panel, with average GI50 of 4.6±2 μm . This newly developed family of TiIV complexes is thus of great potential for anticancer therapy. 相似文献
98.
Single crystals of a new silicate carbonate, K2Ca[Si2O5](CO3), have been synthesized in a multi-components hydrothermal solution with a pH value close to neutral and a high concentration of a carbonate mineralizer. The new compound has an axial structure (s.g. P6322) with unit cell parameters a = 5.04789 (15), c = 17.8668 (6) Å. Pseudosymmetry of the structure corresponds to s.g. P63/mmc which is broken only by one oxygen position. The structure consists of two layered fragments: one of the type of the mineral kalsilite (KAlSiO4) and the other of the high-temperature soda-like α-Na2CO3, Ca substituting for Na. The electro-neutral layer K2[Si2O5] (denoted K) as well as the layer Ca(CO3) (denoted S) may separately correspond to individual structures. In K2Ca[Si2O5](CO3) the S-K layers are connected together via Ca-O interactions between Ca atoms from the carbonate layer and apical O atoms from the silicate one, and also via K-O interlayer interactions. A hypothetical acentric structure, sp.gr. P-62c, is predicted on the basis of the order-disorder theory. It presents another symmetrical option for the arrangement of K-layers relative to S-layers. The K,Ca-silicate-carbonate powder produces a moderate SHG signal that is two times larger that of the α-quartz powder standard and close to other silicates with acentric structures and low electronic polarizability. 相似文献
99.
Li Zhang Dr. Julie Jung Dr. Peng Zhang Mei Guo Dr. Lang Zhao Prof. Dr. Jinkui Tang Prof. Dr. Boris Le Guennic 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1392-1398
Elaborate chemical design is of utmost importance in order to slow down the relaxation dynamics in single‐molecule magnets (SMMs) and hence improve their potential applications. Much interest was devoted to the study of distinct relaxation processes related to the different crystal fields of crystallographically independent lanthanide ions. However, the assignment of the relaxation processes to specific metal sites remains a challenging task. To address this challenge, a new asymmetric Dy2 SMM displaying a well‐separated two‐step relaxation process with the anisotropic centers in fine‐tuned local environments was elaborately designed. For the first time a one‐to‐one relationship between the metal sites and the relaxation processes was evidenced. This work sheds light on complex multiple relaxation and may direct the rational design of lanthanide SMMs with enhanced magnetic properties. 相似文献
100.
Dr. Jingjun Hao Prof. Arnold L. Rheingold Marzieh Kavand Dr. Kipp J. van Schooten Prof. Christoph Boehme Dr. Marçal Capdevila‐Cortada Prof. Juan J. Novoa Eva Wöss Prof. Günther Knör Prof. Joel S. Miller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12312-12315
The reaction of 2,3,5,6‐tetracyanopyridine (TCNPy) and Cr(C6H6)2 forms diamagnetic σ‐[TCNPy]22? possessing a 1.572(3) Å intrafragment sp3–sp3 bond. This is in contrast to the structurally related 1,2,4,5‐tetracyanobenzene and 1,2,4,5‐tetracyanopyrazine that form π‐dimer dianions possessing long, multicenter bonds. 相似文献