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《化学:亚洲杂志》2017,12(10):1043-1047
High‐silica RHO zeolite was directly synthesized using an alkali metal‐crown ether (AMCE) complex as organic structure‐directing agent (OSDA). Derived from the UV‐vis spectra and zeolite patterns, the crown ether‐cesium cation interaction was found to have crucial effect on the enhancement of silica content within the zeolite framework. The synthesized RHO zeolites possess up to four times larger silica/alumina ratio (SAR) values than that in their conventional form, which gives them extraordinarily rigid frameworks even after hydrothermal aging under 800 °C. Compared to commercial zeolites, copper‐exchanged high‐silica RHO zeolites demonstrate considerably high reaction activity in NOX removal, making them promising candidates for diesel exhaust treatment. 相似文献
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Fang-Fang Wang Zhi-Ru Li Di Wu Xiao-Ying Sun Wei Chen Ying Li Chia-Chung Sun 《Chemphyschem》2006,7(5):1136-1141
Optimized structures, with all real frequencies, of superalkali superhalides (Li(3))(+)(SH)(-) (SH=LiF(2), BeF(3), and BF(4)), are obtained, for the first time, at the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ computational levels. These superalkali superhalides possess three characteristics that are significantly different from normal alkali halides. 1) They have a variety of structures, which come from five bonding mode types: edge-face, edge-edge, face-face, face-edge, and staggered face-edge. We find that the bonding mode type closely correlates with the Li(3)-SH bond energy. 2) The valence electrons on the Li(3) ring are pushed out by the (SH)(-) anion, and become excess electrons, conferring alkalide or electride characteristics on these Li(3)-SH species, depending on the bonding mode type. 3) The highest occupied molecular orbital of each Li(3)-SH species is a doubly occupied delocalized sigma bonding orbital on the Li(3) ring, which indicates its aromaticity. It is noticeable that the maximum negative nucleus-independent chemical shift value (about -10 ppm) moves out from the center of the Li(3) ring, owing to repulsion by the SH(-) anion. We find that these superalkali superhalides are not only complicated "supermolecules", but are also a new type of alkalide or electride, with aromaticity. 相似文献
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Dr. Nan Li Botao Wu Chao Yu Tianyu Li Prof. Dr. Wen-Xiong Zhang Prof. Dr. Zhenfeng Xi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8953-8957
Benzene, a common aromatic compound, can be converted into an unstable antiaromatic 8π-electron intermediate through two-electron reduction. However, as an isoelectronic equivalent of benzene, borazine (B3N3Ph6), having weak aromaticity, undergoes a totally different two-electron reduction to afford (B3N3R6)2− homoaromatic compounds. Reported here is the synthesis of homoaromatic (B3N3Ph6)2− by the reduction of B3N3Ph6 with either potassium or rubidium in the presence of 18-crown-6 ether. Theoretical investigations illustrate that two electrons delocalize over the three boron atoms in (B3N3Ph6)2−, which is formed by the geometric and orbital reorganization and exhibits (π,σ)-mixed homoaromaticity. Moreover, (B3N3Ph6)2− can act as a robust 2e reductant for unsaturated compounds, such as anthracene, chalcone, and tanshinones. This 2e reduction is of high efficiency and selectivity, proceeds under mild reaction conditions, and can regenerate neutral borazine. 相似文献
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Nan Li Botao Wu Chao Yu Tianyu Li Wen‐Xiong Zhang Zhenfeng Xi 《Angewandte Chemie (International ed. in English)》2020,59(23):8868-8872
Benzene, a common aromatic compound, can be converted into an unstable antiaromatic 8π‐electron intermediate through two‐electron reduction. However, as an isoelectronic equivalent of benzene, borazine (B3N3Ph6), having weak aromaticity, undergoes a totally different two‐electron reduction to afford (B3N3R6)2? homoaromatic compounds. Reported here is the synthesis of homoaromatic (B3N3Ph6)2? by the reduction of B3N3Ph6 with either potassium or rubidium in the presence of 18‐crown‐6 ether. Theoretical investigations illustrate that two electrons delocalize over the three boron atoms in (B3N3Ph6)2?, which is formed by the geometric and orbital reorganization and exhibits (π,σ)‐mixed homoaromaticity. Moreover, (B3N3Ph6)2? can act as a robust 2e reductant for unsaturated compounds, such as anthracene, chalcone, and tanshinones. This 2e reduction is of high efficiency and selectivity, proceeds under mild reaction conditions, and can regenerate neutral borazine. 相似文献
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Theoretical studies on structures and nonlinear optical properties of alkali doped electrides B12N12–M (M = Li,Na, K)
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The structures and nonlinear optical properties of a novel class of alkali metals doped electrides B12N12–M (M = Li, Na, K) were investigated by ab initio quantum chemistry method. The doping of alkali atoms was found to narrow the energy gap values of B12N12 in the range 3.96–6.70 eV. Furthermore, these alkali metals doped compounds with diffuse excess electron exhibited significantly large first hyperpolarizabilities (β0) as follows: 5571–9157 au for B12N12–Li, 1537–18,889 au for B12N12–Na, and 2803–11,396 au for B12N12–K. Clearly, doping of the alkali atoms could dramatically increase the β0 value of B12N12 (β0 = 0). Furthermore, their transition energies (ΔE) were also calculated. The results showed that these compounds had low ΔE values in the range 1.407–2.363 eV, which was attributed to large β0 values of alkali metals doped B12N12 nanocage. © 2016 Wiley Periodicals, Inc. 相似文献
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Herance JR Concepción P Doménech A Bourdelande JL Marquet J García H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6491-6502
Zeolites are suitable microporous hosts for positively charged organic species, but it is believed that they cannot adsorb organic anions. Pure Meisenheimer complex, derived from reduction of 2,4-dinitroaniline with NaBH4, was adsorbed inside faujasite cavities. Evidence for the internal incorporation of this negatively charged reaction intermediate comes from 1) XPS elemental analysis as a function of the depth of penetration into the particle, 2) the remarkable blue shift in lambda(max) of the Meisenheimer complex adsorbed on zeolite (ca. 470 nm) as compared to that in acetonitrile (580 nm) and 3) from the lack of reactivity with size-excluded hydride-acceptor reagents. Evidence is provided in support of an adsorption mechanism in which a neutral ion pair (alkali metal ion + Meisenheimer anion) is the actual species being adsorbed. In fact it appears that there is remarkable increase in the association constant for the ion-pair complex within the zeolite cavities as compared to DMF solution. Although this mechanism of adsorption as an ion-pair complex has precedents in the adsorption of some inorganic salts, what is novel is the notable increase in the stability and persistence of the Meisenheimer anion (a anionic reaction intermediate) as a result of zeolite inclusion. Adsorbed Meisenheimer complex exhibits much lower reactivity towards electron acceptors, oxygen, and water. Cyclic voltammetry of zeolite-modified electrodes reveals for the Meisenheimer complex adsorbed on LiY a reversible redox peak that is not observed in solution and has been interpreted as arising from site isolation and stabilisation of the electrochemically generated species. 相似文献
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Lei Wang Nana Yan Xiaona Liu Xuebin Zhao Meikun Shen Leifeng Liu Peng Tian Peng Guo Zhongmin Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(4):1029-1036
Tailoring the morphology of a specific crystalline material through distinct crystal growth mechanisms (classical and nonclassical) is challenging. Herein, we report the two unique morphologies of a medium-pore (10×8-ring) zeolite, ZSM-57, prepared by employing an identical organic structure-directing agent (OSDA) and different inorganic cations, namely Na+ and K+, denoted as ZSM-57-Na (pentagonal nanoplates) and ZSM-57-K (pentagonal nanoprisms), respectively. The tunable twin domain size and twin boundaries in both samples have been unraveled at the atomic level by electron crystallography. It is of significance to note that the 10-ring pore openings run perpendicular to the pentagonal nanoplates and nanoprisms. Moreover, the distinct crystal growth mechanisms, which result in the different unique morphologies and tunable twin domains, were further determined by electron crystallography combined with other techniques. Nonclassical growth involving the aggregation of amorphous aluminosilicate nanoparticles to the smooth ZSM-57-Na crystal surface dominates the ZSM-57-Na crystallization process. For the ZSM-57-K sample, the classical layer-by-layer growth through the addition of silica molecules to advancing steps on the crystal surface dominates the ZSM-57-K crystallization process. The different morphologies of both samples result in the distinct catalytic lifespan of the methanol conversion and selectivity of lower olefins. 相似文献
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Xin‐Bao Han Zhi‐Ming Zhang Zhi‐Shu Wang Huan Zhang Hui Duan En‐Bo Wang 《ChemInform》2012,43(22):no-no
K2NaH2 [BW12O40]·12H2O, prepared by the conventional aqueous method, is characterized by single crystal XRD and IR spectroscopy. 相似文献
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Maksim Kulichenko Nikita Fedik Prof. Dr. Konstatin V. Bozhenko Prof. Dr. Alexander I. Boldyrev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(20):5311-5315
Growing demands of material science and, in particular, in the field of nonlinear optics (NLO) encourage us to look for stable highly polarizable molecules with excess diffuse electrons. An unusual class of compounds called electrides comply with these requirements. Many attempts have been made, yet only few electrides have been synthesized as solids and none of them as molecular species. In this paper, a new theoretically designed molecular species with electride characteristics is reported. The idea of this molecular electride comes from the formation of electride-like features in the MgO crystal with defect F-centers. The geometry of the investigated molecule can be described as a Mg4O4 cube with one oxygen atom removed. In Mg4O3, two 3s electrons are pushed out from the inner area of the molecule forming a diffuse electride multicentered bond. Our calculations show that this electride-like cluster possesses a noticeably large first hyperpolarizability β=5733 au. At the same time, a complete cube Mg4O4 and Mg4O32+ without electride electron pair have much smaller β: 0 au and 741 au, respectively. This fact indicates the decisive role of the electride electron pair in NLO properties. Additionally, vertical detachment energies of isomers (VDE), excitation energies ΔE, polarizabilities α, and IR spectra were calculated. These properties, including β, are supposed to be observable experimentally and can serve as indirect evidence of the stable molecular electride formation. 相似文献
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Zheng Zhou Lin Fu Yunbin Hu Xiao‐Ye Wang Zheng Wei Akimutsu Narita Klaus Müllen Marina A. Petrukhina 《Angewandte Chemie (International ed. in English)》2020,59(37):15923-15927
Chemical reduction of a benzo‐fused double [7]helicene ( 1 ) with two alkali metals, K and Rb, provided access to three different reduced states of 1 . The doubly‐reduced helicene 1 2? has been characterized by single‐crystal X‐ray diffraction as a solvent‐separated ion triplet with two potassium counterions. The triply‐ and tetra‐reduced helicenes, 1 3? and 1 4?, have been crystallized together in an equimolar ratio and both form the contact‐ion complexes with two Rb+ ions each, leaving three remaining Rb+ ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of 1 , the central axis of helicene becomes more compressed upon electron addition (1.42 Å in 1 4? vs. 2.09 Å in 1 ). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in 1 to 20.7° in 1 4?. Theoretical calculations provided the pattern of negative charge build‐up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X‐ray crystallographic and NMR spectroscopic data. 相似文献
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石墨烯(graphene)是近年被发现和合成的一种新型二维平面纳米碳质材料。由于其新奇的物理和化学性质,石墨烯已经成为了备受瞩目的科学新星,是纳米材料领域的一大研究热点。在石墨烯的研究中,基于石墨烯的无机纳米复合材料是石墨烯迈向实际应用的一个重要方向。本文在简要介绍石墨烯的结构、性质和制备方法的基础上,重点就近年来以石墨烯为基体的无机物(主要包括金属和半导体)纳米复合材料的合成和应用作一述评,并对石墨烯基无机纳米复合材料的研究和发展方向作了展望。 相似文献
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Suélio Marques Marcos A. Castro Renato B. Pontes Salviano A. Leão Tertius L. Fonseca 《International journal of quantum chemistry》2020,120(3):e26093
This work reports the results of the vibrational corrections and frequency dependence to the first hyperpolarizabilities of the alkali- and alkaline-earth-doped boron nitride nanotubes. The electronic contributions were computed by means of the density functional theory with the M06-2X functional, and the vibrational corrections were calculated using the perturbation theoretical method and the field-induced coordinates methodology. The results for the electronic contribution show that such materials exhibit large first hyperpolarizabilities and electride characteristic. We also show that the distribution of the excess electron, which originates from the doping atoms, plays an important role in the large electronic hyperpolarizabilities (βel). Moreover, our findings strongly indicate that the effect of vibrations on the hyperpolarizabilities can be quite important and can even be much larger than the electronic counterpart. 相似文献
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Mengyu Qi Chuankai Tang Dr. Zhongjun Zhou Prof. Fang Ma Prof. Dr. Yirong Mo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6234-6239
Converting CO2 into high-value chemicals has been regarded as an important solution for a sustainable low-carbon economy. In this work, we have theoretically designed an innovative strategy for the absorption and activation of CO2 by the electride N3Li, that is, 1,3,5(2,6)-tripyridinacyclohexaphane (N3) intercalated by lithium. DFT computations showed that the interaction of CO2 with N3Li leads to the catalytic complex N3Li(η2-O2C), which can initiate the radical-controlled reduction of another CO2 to form organic acids through radical reactions in the gas phase. The CO2 reduction consists of four steps: (1) The formation of N3Li(η2-O2C) through the combination of N3Li and CO2, (2) hydrogen abstraction from RH (R=H, CH3, and C2H5) by N3Li(η2-O2C) to form the radical R. and N3Li(η2-O2C)H, (3) the combination of CO2 and the radical R. to form RCOO., and (4) intermolecular hydrogen transfer from the intermediate N3Li(η2-O2C)H to RCOO.. In the whole reaction process, the CO2 moiety in the complex N3Li(η2-O2C) maintains a certain radical character at the carbon atom of CO2 and plays a self-catalyzing role. This work represents the first example of electride-sponsored radical-controlled CO2 reduction, and thus provides an alternative strategy for CO2 conversion. 相似文献
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M. Olczak-Kobza 《Journal of Thermal Analysis and Calorimetry》1992,38(6):1487-1495
The thermal properties of the anthranilates of the alkali metals Li, Na, K, Rb and Cs were studied. Thermal, chemical and X-ray analyses and infrared spectroscopy were used to determine the reactions of decomposition of these compounds. The thermal properties of the anthranilates of the alkali metals were compared with those of other metals.This work was done within Project 01.17: New Methods in Analytical Chemistry and Their Application in the National Economy. 相似文献