Crystalline Behavior and Structure of a Liquid Crystal Compound, 5‐{[4′‐(((Pentyl)oxy)‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne

Single crystals of two liquid crystal compounds, 5‐{[4′‐(((pentyl)oxy)‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO5) and 5‐{[(4′‐nonyloxy‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO9), have been prepared by solution growth technique. The morphologies and structures of A3EO5 and A3EO9 crystals were investigated by wide angle X‐ray diffraction (WXRD), atom force microscope (AFM) and transmission electron microscope (TEM). In contrast to the same series of compounds which have a longer alkyl tail, 5‐{[(4′‐heptoxy‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO7), 5‐{[(4′‐heptoxy‐4‐biphenylyl)oxy]carbonyl}‐1‐pentyne (A3E′O7) and A3EO9, A3EO5 shows strikingly different crystalline behavior. The former three compounds have only one crystal form, whereas A3EO5 exhibits polymorphism. Specifically, A3EO5 crystals grown from toluene solution show two crystal forms. The first one is crystal I which adopts a monoclinic P112/m space group with unit cell parameters of a?5.79 Å, b?8.34 Å, c?43.92 Å, γ?96°, and the other one is crystal II which adopts a monoclinic P112 space group with unit cell parameters of a?5.55 Å, b?7.38 Å, c?31.75 Å, γ?94°. When using dioxane as the solvent to grow A3EO5 crystal, we can selectively obtain crystal I. A3EO5 melt‐grown crystals also have two crystal forms which derive from crystal I and crystal II, respectively. The different crystalline behavior of the compounds should correlate with their different electron dipole moment resulting from the different length of alkyl tail.     

单分子膜诱导下的矿物晶体生长

介绍了近几年单分子膜诱导下矿物晶体生长的最新进展。讨论了单分子膜诱导下的矿物晶体生长与溶溶中的异同,成膜材料,单分子膜性质和聚集态,矿物晶体的选择性及晶体的表征方法。     

Nucleation: What Happens at the Initial Stage?

Crystallizing growth : The initial structure of crystal nuclei is supersaturation‐dependent. At low degrees of supersaturation, liquid‐like nuclei are formed initially, which undergo a continuous structure transition from liquid‐like to crystal‐like as the size N increases. This gradual structure evolution substantially lowers the nucleation barrier ΔG* and facilitates the nucleation relative to the formation of crystal‐like clusters from the beginning.

     

Kristallstruktur von Hexamincyclotriphosphazen,P3N3(NH2)6

Crystal Structure of Hexamine Cyclotriphosphazene, P₃N₃(NH₂)₆ In the presence of KNH₂ hexamine cyclotriphosphazene semi ammoniate (molar ratio 12:1) in NH₃ gives crystals of solvent free P₃N₃(NH₂)₆ within 5 d at 130°C and p(NH₃) = 110 bar. The structure was solved by X-rax methods: P₃N₃(NH₂)₆: P2₁/c, Z = 4, a = 10.889(6) Å, b = 5.9531(6) Å, c = 13.744(8) Å, β = 97.83(3)°, Z(F_o) = 1 721 with (F_o)² ≥ 3σ(F_o)², Z(var.) = 157, R/R_w = 0,036/0,041 The structure contains columns of molecules P₃N₃(NH₂)₆ all in the same orientation. The six-membered rings within one molecule have boat conformation. The columns are stacked together in a way that one is surrounded by four others shifted by half a lattice constant in direction [010]. Strong hydrogen bridge-bonds N? H…?N connect molecules within the columns and between them.     

Kristallstrukturanalyse von (NH4)2NaInF6

Single Crystal Structure of (NH₄)₂NaInF₆ (NH₄)₂NaInF₆ has been synthesized via a novel route from In₂O₃, NaF and NH₄F and its crystal structure has been determined using single crystal techniques (Fm3 m, a = 8.6675(3) Å, Z = 4, 4 106 reflections, R = 0.007). The crystal structure derives from the elpasolite type of structure, the ammonium ions are not disordered.     

配液结晶法制备溶菌酶蛋白质晶体的生长机理研究

采用配液结晶法制取了溶菌酶蛋白质晶体, 使用动态光散射测量了溶液中聚集体的颗粒度几率分布; 使用Zeiss显微镜测定了溶菌酶(110)晶面的生长速度. 实验表明: 随着蛋白质和NaCl浓度的增加, 溶液中聚集体的颗粒尺寸也相应增加. 随着反应时间的增加, 溶菌酶分子在溶液中的聚集反应, 逐渐达到平衡; 在蛋白质和NaCl浓度较高时, 溶菌酶晶体的(110)面生长较快, 而在蛋白质和NaCl浓度较低时, 该晶面生长较慢. 基于二维成核生长机理, 从晶体生长动力学理论方程出发, 计算了二维成核的形成能α＝4.01×10^－8 J•cm^－2.     

亚稳碘化汞(β-HgI2M)晶体生长与相变

采用溶液法,以α-HgI_2为原料,在DMSO和H_2O混合溶剂中生长了β-HgI_2~M晶体。通过XRD检测了晶体的结构特征,利用偏光显微镜研究了晶体生长的动态过程及β-HgI_2M→α-HgI_2的相变过程。研究表明,生长的晶体为β-HgI_2~M,空间结构为Cmc2_1;晶体生长界面夹角为65.02°,与β-HgI_2~M单胞中(110)和(110)夹角(65.16°)吻合;β-HgI_2~M→α-HgI_2相变为结构重构的一级相变。     

亚稳碘化汞(β-HgI2M)晶体生长与相变

采用溶液法,以α-HgI₂为原料,在DMSO和H₂O混合溶剂中生长了β-HgI₂^M晶体。通过XRD检测了晶体的结构特征,利用偏光显微镜研究了晶体生长的动态过程及β-HgI₂^M→α-HgI₂的相变过程。研究表明,生长的晶体为β-HgI₂^M,空间结构为Cmc2₁;晶体生长界面夹角为65.02°,与β-HgI₂^M单胞中(110)和(110)夹角(65.16°)吻合;β-HgI₂^M→α-HgI₂相变为结构重构的一级相变。     

Effect of inorganic anions on the morphology and structure of magnesium calcite

Calcium carbonate was precipitated from calcium hydroxide and carbonic acid solutions at 25 degrees C, with and without addition of different magnesium (MgSO(4), Mg(NO(3))(2) and MgCl(2)) and sodium salts (Na(2)SO(4), NaNO(3) and NaCl) of identical anions, in order to study the mode of incorporation of magnesium and inorganic anions and their effect on the morphology of calcite crystals over a range of initial reactant concentrations and limited c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios. The morphology, crystal size distribution, composition, structure, and specific surface area of the precipitated crystals, as well as the mode of cation and anion incorporation into the calcite crystal lattice, were studied by a combination of optical and scanning electron microscopy (SEM), electronic counting, a multiple BET method, thermogravimetry, FT-IR spectroscopy, X-ray diffraction (XRD), and electron paramagnetic resonance (EPR) spectroscopy. In the systems of high initial relative supersaturation, precipitation of an amorphous precursor phase preceded the formation of calcite, whereas in those of lower supersaturation calcite was the first and only polymorphic modification of calcium carbonate that appeared in the system. The magnesium content in calcite increased with the magnesium concentration in solution and was correlated with the type of magnesium salt used. Mg incorporation caused the formation of crystals elongated along the calcite c axis and, in some cases, the appearance of new [011] faces. Polycrystalline aggregates were formed when the c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios in solution were increased. Addition of sulfate ions, alone, caused formation of spherical calcite polycrystalline aggregates.     

Oriented Crystallization on Organic Monolayers to Control Concomitant Polymorphism

Nucleation events and crystal growth can be guided by molecular recognition at interfaces through intermolecular interactions. The short-acting antimicrobial sulfa drug sulfathiazole is known for its concomitant crystallization, which has five known polymorphs, due to conformational flexibility and hydrogen-bond synthon variation. In its development stage of a drug the issue of concomitant crystallization needs to be addressed with respect to patent litigation, including legal actions to protect patents against infringement. A functional self-assembled monolayer (SAM) of organic thiol on a gold surface has been employed as an efficient approach to control concomitant nucleation of such flexible drugs. The crystallization on a SAM surface is mostly kinetically driven and often leads to the nucleation of novel metastable forms. Spectroscopic, thermal analysis and X-ray diffraction studies reveal that a previously unknown, sixth form of the drug nucleates on the designed SAM surface.     

Optical Properties of Ce-Doped Lithium Niobate Crystals with Various Li/Nb Ratio

Ce-doped lithium niobate （LiNbO3） single crystals were grown from the melts with various Li/Nb molar ratios （0.750, 0.850, 0.946, 1.100, 1.250 and 1.380） by Czochralski method, while doping concentration of Ce was 0.1 mol%. Infrared spectra （IR） and Ultraviolet-visible absorption spectra （UV） of the crystals were measured to investigate the location of Ce ions and defect structure in crystals. The writing time, erasing time, photorefractive sensitivity and dynamic range were measured by two-wave coupling equipment. The results showed that Ce takes the place of Li lattice site, and the LiNbO3 crystal grown from the melt with Li/Nb ratio of 1.250 is stoichiometric crystal, which has the best properties due to the synergistic effect of Ce ion and Li/Nb ratio. Also the influence of various Li/Nb ratios on the defect structure and optical properties of the crystal was reported.     

One-step synthesis of novel flower-like Sn-doped ZnO architectures with enhanced photocatalytic activity

A facile hydrothermal method to synthesize flower-like Sn-doped ZnO (FLSn-ZnO) nanostructures is described. The obtained hierarchical architectures of FLSn-ZnO are found to be assembled with abundant regular-shaped nanosheets and nanoparticles. A possible formation mechanism is proposed on the base of a series of control experiments. The tests show that FLSn-ZnO architectures exhibit higher photocatalytic activity in the degrading Rhodamine B and tetracycline aqueous solution than pure ZnO under UV-light irradiation. And photocurrent response and photoluminescence of ZnO and FLSn-ZnO demonstrates that in photocatalytic performance, the latter is higher.     

Photoinduced Ratchet‐Like Rotational Motion of Branched Molecular Crystals

Photomechanical molecular crystals can undergo a variety of light‐induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH‐driven reprecipitation has been used to grow branched microcrystals of the anthracene derivative 4‐fluoroanthracenecarboxylic acid. When these microcrystals are illuminated with light of λ=405 nm, an intermolecular [4+4] photodimerization reaction drives twisting and bending of the individual branches. These deformations drive a rotation of the overall crystal that can be repeated over multiple exposures to light. The magnitude and direction of this rotation vary because of differences in the crystal shape, but a typical branched crystal undergoes a 50° net rotation after 25 consecutive irradiations for 1 s. The ability of these crystals to undergo ratchet‐like rotation is attributed to their chiral shape.     

Polymer-induced alignment of DL-alanine nanocrystals to crystalline mesostructures

Crystallization of DL-alanine by cooling of a supersaturated solution in the presence of a chiral double-hydrophilic block copolymer poly(ethylene glycol)-block-poly(ethylene imine)-S-isobutyric acid (PEG4700-PEI1200-S-iBAc) yields crystal superstructures with an astonishing morphology. Although analysis by light microscopy reveals these crystals to be apparently well facetted, electron microscopy shows that they consist of three-dimensionally, well-aligned nanocrystals that are scaffolded to a so-called mesocrystal. This mesocrystal is formed by polymer-mediated structuration, and provides evidence for the importance of mesoscopic events in a typical crystallization process.     

Contributions on thermal behaviour and crystal chemistry of anhydrous phosphates. XIX. Tri-chromium(II)-bis-phosphate Cr3(PO4)2 (≙ Cr6(PO4)4) – A transition metal(II)-orthophosphate with new structure type

Deep blue-violet single crystals of hitherto unknown chromous orthophosphate have been obtained reducing CrPO₄ by elemental Cr at temperatures above 1050°C in evacuated silica ampoules (NH₄I or I₂ as mineraliser). The complex structure of Cr₃(PO₄)₂ (P2₁2₁2₁, Z = 8, a = 8.4849(10) Å, b = 10.3317(10) Å, c = 14.206(2) Å) contains six crystallographically independent Cr²⁺ per unit cell. Five of them are coordinated by four oxygen atoms which form a distorted (roof shaped) square plane as first coordination sphere at interatomic distances 1.96 Å ? d(Cr? O) ? 2.15 Å. Their coordination is completed by additional oxygen atoms (2 or 3) at distances 2.32 Å ? d(Cr? O) ? 3.21 Å. The sixth Cr²⁺ shows six-fold octahedral coordination with strong radial distortion (d(Cr? O): 1.97, 2.04, 2.15, 2.28, 2.29, 2.53 Å). The four different [PO₄] groups exhibit only minor deviations from ideal tetrahedral geometry (1.51 Å ? d(P? O) ? 1.57 Å, 104.3° ? ∠(O? P? O) ? 114.4°). An unusually low magnetic moment μ_exp = 4.28(2) μ_B (θ_P = ?54.8(5) K) has been observed for Cr²⁺.     

Hierarchical CaCO3 Chromatography: A Stationary Phase Based on Biominerals

In biomineralization, acidic macromolecules play important roles for the growth control of crystals through a specific interaction. Inspired by this interaction, we report on an application of the hierarchical structures in CaCO₃ biominerals to a stationary phase of chromatography. The separation and purification of acidic small organic molecules are achieved by thin‐layer chromatography and flash chromatography using the powder of biominerals as the stationary phase. The unit nanocrystals and their oriented assembly, the hierarchical structure, are suitable for the adsorption site of the target organic molecules and the flow path of the elution solvents, respectively. The separation mode is ascribed to the specific adsorption of the acidic molecules on the crystal face and the coordination of the functional groups to the calcium ions. The results imply that a new family of stationary phase of chromatography can be developed by the fine tuning of hierarchical structures in CaCO₃ materials.     

Growth of Shape‐ and Size‐Selective Zinc Oxide Nanorods by a Microwave‐Assisted Chemical Bath Deposition Method: Effect on Photocatalysis Properties

Herein, we demonstrate the shape‐ and size‐selective growth of ZnO nanostructures on indium tin oxide‐coated glass substrates by using a microwave‐assisted chemical bath deposition method. By systematically controlling the deposition parameters, it is possible to produce shape‐ and size‐selective nanostructures with high alignment and uniformity. Specifically, the pH of the bath can be used to control the shape of rods from bundled structures to tapered and flat tips. Furthermore, the deposition temperature can be used to control the size of the ZnO array from 770 to 125 nm. The prepared rods were active catalysts in the degradation of methylene blue under UV radiation, and exhibited size‐dependent activity.     

大颗粒磷钼酸铵:制备与结晶动力学(英文)

通过缓慢滴加焦磷酸钾的硝酸溶液到钼酸铵溶液中制得了大颗粒磷钼酸铵(AMP)。研究了AMP的成核速率(G)与晶体生长速率。与晶体生长速率相比成核速率的反应级数更高。最初,大颗粒磷钼酸铵的结晶过程处于相变反应控制的动力学区域,此时溶液的过饱和生成速率比过饱和消除速率高。晶体线生长速率与溶液的过饱和度先增加后降低。在滴加中期,过饱和消除速率增长到与其生成速率相当。在滴加后期,晶体成核速率快速增高,而晶体的线生长速率下降。晶体的成核速率成为过饱和消除的唯一控制步骤。因此,AMP成核大部分是在首先接触到滴加液的局部溶液中完成的。     

Controllable Zeolite AST Crystallization: Between Classical and Reversed Crystal Growth

Crystal growth mechanisms govern a wide range of properties of crystalline materials. Reversed crystal growth is one of the nonclassical mechanisms observed in many materials. However, the reversed crystallization starting from amorphous aggregates and the key factors driving this growth remain elusive. Here, we describe a characteristic model of reversed crystal growth representing the inner structure and crystallinity development of aggregates studied by microscopy and nano X-ray computed tomography. By adjusting the synthesis conditions, the fundamental function of the structure-directing agent, which determines the crystallization pathway, was revealed. As a result, the crystal growth mode can be “switched” from the classical route at a low ratio of SDA/framework elements to reversed growth at a high ratio. Our findings provide further insights into crystal growth control, which is crucial for improving synthesis protocols and designing various forms of crystalline materials.