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11.
Hai‐Tao Zhou Chang‐Feng Wang Yao Liu Xiao‐Wei Fan Kang Yang Wen‐Juan Wei Yun‐Zhi Tang Yu‐Hui Tan 《化学:亚洲杂志》2019,14(21):3946-3952
Molecular ferroelectrics have displayed a promising future since they are light‐weight, flexible, environmentally friendly and easily synthesized, compared to traditional inorganic ferroelectrics. However, how to precisely design a molecular ferroelectric from a non‐ferroelectric phase transition molecular system is still a great challenge. Here we designed and constructed a molecular ferroelectric by double regulation of the anion and cation in a simple crown ether clathrate, 4 , [K(18‐crown‐6)]+[PF6]?. By replacing K+ and PF6? with H3O+ and [FeCl4]? respectively, we obtained a new molecular ferroelectric [H3O(18‐crown‐6)]+[FeCl4]?, 1 . Compound 1 undergoes a para‐ferroelectric phase transition near 350 K with symmetry change from P21/n to the Pmc21 space group. X‐ray single‐crystal diffraction analysis suggests that the phase transition was mainly triggered by the displacement motion of H3O+ and [FeCl4]? ions and twist motion of 18‐crown‐6 molecule. Strikingly, compound 1 shows high a Curie temperature (350 K), ultra‐strong second harmonic generation signals (nearly 8 times of KDP), remarkable dielectric switching effect and large spontaneous polarization. We believe that this research will pave the way to design and build high‐quality molecular ferroelectrics as well as their application in smart materials. 相似文献
12.
13.
Zhenguang Lin Huayang Chen Junning Zhuang Yang Wu Yujuan Lin 《Journal of inclusion phenomena and macrocyclic chemistry》1998,30(1):13-19
A new clathrate inclusion compound of 2,3:11,12:20,21:29,30-tetrabenzo-1,13,16,19,31,34-hexaoxa-5,6,8,9,23,24,26,27- octaaza-7,25-dithioketone-2,3:4,5:9,10:11,12:22,23:27,28:29,30-cyclo-[36]ene([ 36]eneO6N8), which contains THF, has been prepared and crystallizes in the monoclinic space group P21/n with a = 9.829(5)Å, b = 24.23(1)Å, c = 10.181(9)Å, = 92.93(5)-. Each unit cell contains two [36]ene-O6N8 molecules and four THF molecules. The [36]ene-O6N8 molecule lies on the crystallographic centre of symmetry and a pair of the THF molecules with half-chair conformation are located within rectangular channels formed by the macrocycle molecules. 相似文献
14.
I.?S.?TerekhovaEmail author a?A.?Yu.?Manakov V.?V.?Feklistov Yu.?A.?Dyadin V.?YU.?Komarov D.?Yu.?Naumov 《Journal of inclusion phenomena and macrocyclic chemistry》2005,52(3-4):207-211
X-ray powder diffraction studies were performed of the polyhydrates, formed at positive temperature in swelled grains of carboxylic cation-exchange resins in the form of tetraisoamylammonium (cross-linked tetraisoamylammonium polyacrylates, differing in the degree of cross-linking: 1, 2 and 3%). It was shown that the polyhydrates exist as the crystalline phase under specific conditions, determined earlier by DTA technique. Diffraction patterns of the samples, recorded at the temperature +3 ± 1 °C, indicate that the polyhydrates crystallize in hexagonal symmetry, the unit cell parameters are close to a=12.25 Å, c=12.72 Å and do not depend significantly upon the degree of cross-linking. The suppositions were made concerning the size of hydrate crystallites, formed in the swelled grains of the studied resins.This revised version was published online in July 2005 with a corrected issue number. 相似文献
15.
Equilibrium molecular dynamics (MD) simulations have been performed in both the NVT and NPT ensembles to study the structural and dynamical properties of fully occupied methane clathrate hydrates at 50, 125, and 200 K. Five atomistic potential models were used for water, ranging from fully flexible to rigid polarizable and nonpolarizable. A flexible and a rigid model were utilized for methane. The phonon densities of states were evaluated and the localized rattling modes for the methane molecules were found to couple to the acoustic phonons of the host lattice. The calculated methane density of states was found to be in reasonable agreement with available experimental data. 相似文献
16.
Yu. A. Dyadin F. V. Zhurko I. V. Bondaryuk G. O. Zhurko 《Journal of inclusion phenomena and macrocyclic chemistry》1991,10(1):39-56
Experimental data on the investigation of the water-trimethyleneoxide system,P, t, x phase diagram (up to 6 kbar) are presented. The results are compared with those on water systems with ethyleneoxide, 1,3- and 1,4-dioxane, 1,3-dioxolane and tetrahydrofuran, on the basis of which a summarizedP, t, x diagram is plotted for water-cyclic ether systems. It is shown that in all the systems in which a cubic structure II hydrate forms at 1 bar, it eventually turns to cubic structure I under pressure. The nature of high pressure hydrates is discussed.Dedicated to the memory of D. W. Davidson. 相似文献
17.
F. Bottino P. Finocchiaro J. Lipkowski A. Mamo S. Pappalardo K. Suwinska 《Journal of inclusion phenomena and macrocyclic chemistry》1991,11(1):41-48
The crystal and molecular structure of the title compound, C51H57N3O6S3·CH2Cl2 has been determined by single crystal X-ray analysis and refined to anR-value of 0.069 for 1032 reflections. The crystal is trigonal, space groupR3, witha = 21.255(7),c = 11.317(4), andZ = 3. One molecule of dichloromethane used as solvent is enclathrated in the crystal lattice. 相似文献
18.
A. Yu. Manakov J. Lipkowski K. Suwinska M. Kitamura 《Journal of inclusion phenomena and macrocyclic chemistry》1996,26(1-3):1-20
Single crystal X-ray structures of clathrates of -[Ni(NCS)2(4-methylpyridine)4] with furan, tetrahydrofuran, benzene + ethanol, methylene chloride, and methylcellosolve as guests molecules are reported. The location of the guest molecule in the partially decomposed clathrate with methylene chloride was defined by X-ray diffraction and compared with the fully occupied one. The host lattices of all clathrates studied are tetragonal (I41/a) and do not differ significantly from typical -phase clathrates of [M(NCS)2(4-methylpyridine)4] (M = divalent metal cation). Arrangements of guest molecules represent different types of packing: one type of guest molecule occupies both possible types of positions, two different guest molecules occupy different positions, with only one type of positions occupied by one type of guest molecule. Possible stoichiometries of clathrates with -type lattices are discussed.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August 1995. 相似文献
19.
Dietrich Mootz Reinhard Seidel 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(1-2):139-157
The tetramethylammonium hydroxide-water system has been studied by low-temperature differential thermal analysis and X-ray powder diffraction. The melting diagram was constructed for concentrations between 66.7 and 100 mol% H2O. It shows the existence and stability ranges of as many as eight crystalline hydrate phases:- and-Me4NOH·2H2O (phase transition at –85°C, decomposition atca. 105°C), Me4NOH·4 H2O (melting point 44°C, incongruent), and-Me4NOH·5 H2O (phase transition at 42°C, melting point 68°C, congruent),- and-Me4NOH·7.5 H2O (phase transition at 6°C, melting point 16°C, incongruent), and Me4NOH·10 H2O (melting point –20°C, incongruent). The structures of all these phases, except the already known one of-Me4NOH·5 H2O, were determined from single-crystal MoK diffractometer data. The decahydrate and the high-temperature forms of the 7.5-hydrate and the pentahydrate are genuinepolyhedral clathrate hydrates, the first ones reported of a strong base. Their mostly novel three-dimensional anionic host structures, formed by the hydrogen-bonded OH– ions and H2O molecules, arefour-connected throughout, in spite of their proton deficiency which is apparently leveled by disorder. Disorder also affects the enclosed cationic Me4N+ guest species. Like the low-temperature form of the pentahydrate, that of the 7.5-hydrate has a clathrate-related, but not fully polyhedral structure, some of the oxygen atoms being three-connected only. The tetrahydrate presents the rare case of both a hydrogen bond of the type OH–...OH2 and a (deprotonated) water-channel structure. This is fully ordered and apart from that can be derived from the polyhedral one of the-pentahydrate just by removing the appropriate number of water molecules from certain positions. The structures of- and-Me4NOH·2 H2O contain identical one-dimensionalspiro chains [HO–(HOH)/42] with the hydroxide protonnot participating in the hydrogen bonding. The Me4N+ ion is ordered in the and disordered in the phase.Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82076 (66 pages).Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena. 相似文献
20.
Yu. A. Dyadin F. V. Zhurko T. V. Mikina R. K. Udachin 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(1):37-49
P,T,X phase diagrams of the CH2Cl2-H2O, the CHCl3-H2O and the CCl4-H2) systems have been studied by DTA in the pressure range 10–3 to 5.0 kbar. Under pressure the cubic structure II (CS-II) hydrates forming in all the systems are replaced by hydrates with the composition M·7.3 H2O whose stoichiometry and positive dT/dP values of melting lead us to believe that they are CS-I hydrates.In the CH2Cl2 and CHCl3 systems the nonvariant point coordinates of the hydrate transformationQ
2
h
(l1h17h7l2, where l1 and l2 are liquid phases abundant in water and hydrate former, respectively, h17 and h7 are hydrates with hydrate numbers 17 and 7, respectively) areP = 0.6 kbar, T = –1.5°C andP =2.65 kbar,T = –10.5°C, respectively. In the CCl4 system the 4-phaseQ
3
h
point (l1h17h7s, where s is crystalline CCl4) has coordinatesP = 0.75 kbar and T = 0.4°C.The main obstacle of the present study, the very slow achievement of equilibrium, has been eliminated by adding small amounts (0.25% by mass) of surfactants followed by ultrasonic mixing. We have shown that this accelerates the achievement of equilibrium without changing its position. 相似文献