以谷氨酸二乙酯为头基的Bola型两亲分子在气液界面的组装:手性相互作用与膜结构

研究了双头基两亲分子(Bolaamphiphile)N,N′-1,14-十四烷二酸酰-L-谷氨酸二乙酯(L-HDGE)和它的对映异构体D-HDGE在气液界面的组装;考察了HDGE分子的界面组装结构以及头部基团的手性,膜压和离子液体亚相对组装结构的影响.采用原子力显微镜(AFM)和傅里叶变换红外(FTIR)光谱对组装体的微观结构和组装机理进行了研究.结果表明,HDGE(L-HDGE或D-HDGE)在水亚相上可以组装得到平行排列,宽为50-120nm,高为1-5nm的纳米线.而将L-HDGE与D-HDGE混合组装时,只会得到疏松的薄膜结构.红外光谱表明HDGE分子的异手性相互作用强于同手性作用.在表面压继续上升时,纳米线可以发生一定聚集生成纳米带.亚相为一定浓度的离子液体时,会促进分子的聚集,在膜压的共同影响下,纳米带可以卷曲形成螺旋结构,螺旋的方向取决于头基的分子手性.     

热处理对聚己二酸丁二醋多晶结构和降解行为的影响

通过熔融结晶并结合退火处理方法得到多晶结构的聚己二酸丁二酯(PBA)及具有不同热历史的热力学稳定的a晶型,采用广角X射线衍射仪(WAXD)、原子力显微镜(AFM)和差示扫描量热仪(DSC)研究了PBA的多晶结构、晶体尺寸和结晶形貌,跟踪了退火处理PBA的生物降解行为.结果表明,分子链在相同晶格排列中围绕c轴空间取向的不...     

用硬纸板制作晶系模型

自然界里的固体大多数是晶体,晶体是物质在固态时所特有的结构。晶体的外形是构成晶体的质点(离子、原子或分子)在空间的固定点上有规则地排列的内部结构的反映。根据对称性不同可把晶体划分为七个晶系,其中三斜、单斜和斜方晶系对称性最低,属于低级晶族;正方、三方和六方晶系对称性居中,属于中级晶族;等轴晶系对称性最高,属于高级晶族。     

痂囊腔菌素A的结构

对实验室生物合成方法制得的痂囊腔菌素A做X射线晶体衍射测定,与文献对照,所属品系及空间群相同,晶胞参数接近,但发现北醌母体外的侧基构型有明显差异,主要表现在两个手性碳原子是R-R型而非S-S型,分别以衍射数据和分子力学优化数据为起始结构,进行STO-3G水平上的结构全优化。计算结果表明所制得的痂囊腔菌素A是一种新的光学活性对映体,由此推测痂囊腔菌素A的高光敏活性可能与手性结构特征有关。     

α-甘氨酸晶体的动态磁手性和磁电效应

利用变温直流磁化率测定,在外加磁场强度为±1T,磁场平行于晶体b轴,发现在301-302Kα-甘氨酸有动态磁手性相变.α-甘氨酸晶体的每个晶胞包含四个分子,属于具有中心对称结构的P21/n群,电荷中心对称,不导电.在晶体中,两层之间的N (3)—H(8)…O(1)和N (3)—H(8)…O(2)氢键,沿b轴相互交叉反向配对排列.在303K,用原子力显微镜可观察到α-甘氨酸晶体表面分子层与层间有规则的交叉螺旋排列.结合中子衍射确定相变机制为,在相变温度及外加磁场H=±1T时,α-甘氨酸中的N (3)—H(8),电子自旋反转为(邙).因为N (3)—H(8)…O(1)和N (3)—H(8)…O(2)两反向氢键的强度和键角不同,由动态磁手性和磁电效应,产生电荷中心不对称,导致304K附近的热电相变.     

介孔二氧化硅对映选择性吸附的手性印迹调控

使用手性阴离子表面活性剂作为超分子模板, 采用共结构导向法制备手性介孔二氧化硅(CMS), 并运用圆二色谱(CD)对CMS对映选择性吸附结果进行检测, 比较了有无共结构导向剂(CSDA)在介孔表面的排列对吸附选择性的影响. 结果表明, 当使用构型相反的手性超分子模板剂对原合成CMS材料的介孔内表面进行修饰时, 可诱导结构共导向剂N?三甲氧基硅基丙基?N, N, N?三甲基氯化铵(TMAPS)发生手性相反的排列进而导致完全相反的对映选择性吸附. 实验证明此方法合成的CMS的对映选择性吸附及分离能力主要是由修饰在介孔表面的TMAPS螺旋排列形成的手性印迹所导致. 此手性超分子模板诱导TMAPS手性印迹的策略具有一定的普适性, 可对原合成介孔材料对映选择性吸附进行原位调控, 对于拓展其在立体选择性识别、 不对称催化及药物输送等方面的应用具有一定的指导意义.     

α-甘氨酸晶体的动态磁手性和磁电效应

利用变温直流磁化率测定, 在外加磁场强度为依1 T, 磁场平行于晶体b轴, 发现在301-302 K α-甘氨酸有动态磁手性相变. α-甘氨酸晶体的每个晶胞包含四个分子, 属于具有中心对称结构的P21/n群, 电荷中心对称, 不导电. 在晶体中, 两层之间的N+(3)—H(8)…O(1)和N+(3)—H(8)…O(2)氢键, 沿b轴相互交叉反向配对排列. 在303 K, 用原子力显微镜可观察到α-甘氨酸晶体表面分子层与层间有规则的交叉螺旋排列. 结合中子衍射确定相变机制为, 在相变温度及外加磁场H=±1 T时, α-甘氨酸中的N+(3)—H(8),电子自旋反转为(↑). 因为N+(3)—H(8)…O(1)和N+(3)—H(8)…O(2)两反向氢键的强度和键角不同, 由动态磁手性和磁电效应, 产生电荷中心不对称, 导致304 K附近的热电相变.     

石英晶体微天平用于预测非对映体盐结晶分离手性扁桃酸的分离效率

研究了以石英晶体微天平(QCM)手性识别结果预测手性选择剂对外消旋物的手性识别能力的新方法。经过两步组装方式将手性选择剂L-苯丙氨酸(L-Phe)组装到QCM电极表面。通过检测电极共振频率、接触角和X射线光电子能谱的变化对组装结果进行了表征。应用蒸气扩散分子组装(VDMA)方式检测L-Phe修饰QCM电极对L-扁桃酸(MA)的手性识别能力,其手性识别选择性系数约为8。随后用L-Phe作为拆分剂试验了非对映体盐结晶法拆分手性扁桃酸,并优化了手性拆分条件。结果显示,以L-Phe作为拆分剂进行非对映体盐结晶法拆分手性扁桃酸的结果与QCM手性识别结果高度吻合,表明QCM手性识别可用作辅助筛选和预测非对映体盐结晶手性拆分法的手性拆分剂。     

MAH-β-CD的合成及其在毛细管电泳手性拆分中的应用

合成了顺丁烯二酸酐-β-环糊精(MAH-β-CD),并通过红外光谱、质谱对其结构进行表征。以20 mmol/L乙酸铵为缓冲溶液,MAH-β-CD作为手性选择剂,利用毛细管电泳对氨基酸和手性药物对映体进行拆分研究。考察了缓冲溶液pH、分离电压和手性选择剂浓度等对拆分效果的影响,在优化条件下,成功拆分了3种氨基酸(DL-甲硫氨酸、DL-精氨酸、DL-赖氨酸)和两种手性药物(沙丁胺醇、氯美扎酮)对映体,分离度分别为5.11,5.55,2.99,2.33和1.64。     

高效液相色谱手性固定相的研究 Ⅰ.L-缬氨酸-叔丁酰胺型固定相的制备及对映体拆分

本文报道一种新型手性L-缬氨酸-叔丁酰胺型固定相的制备及用它直接拆分对映体的实验。实验结果表明,这种手性固定相对外消旋氨基酸衍生物有较好的拆分效果。洗脱液中异丙醇的含量对拆分效果有较大影响,异丙醇的含量增加,拆分效果下降。拆分样品的结构对总分离度(R_s)也有一定影响,在四种不同洗脱液系统中,DL-苯丙氨酸衍生物的R_s都比DL-缬氨酸衍生物和DL-亮氨酸衍生物小。流量0.6～2.0mL/min时对总分离度无明显影响。实验结果也证明,四种氨基酸衍生物都是D型的先洗脱。     

Amplification of chirality from molecules into morphology of crystals through molecular recognition

We have found a novel type of morphological chiral tuning on inorganic helical crystals through stereochemical recognition of organic molecules. Helical forms consisting of twisted twins emerged from triclinic crystals under diffusion-limited conditions. The proportion of the right- and left-handed helices was precisely tuned with the addition of a specified amount of chiral molecules, such as d- and l-glutamic acids. The chiral molecules recognized the enantiomeric surface of the triclinic crystal and then changed the growth behavior of the helical morphology. As a result, the microscopic chiral information, at a molecular level, was amplified into the macroscopic helices consisting of inorganic achiral components.     

Isostructurality, polymorphism and mechanical properties of some hexahalogenated benzenes: the nature of halogen...halogen interactions

The nature of intermolecular interactions between halogen atoms, X...X (X = Cl, Br, I), continues to be of topical interest because these interactions may be used as design elements in crystal engineering. Hexahalogenated benzenes (C6Cl(6-n)Br(n), C6Cl(6-n)I(n), C6Br(6-n)I(n)) crystallise in two main packing modes, which take the monoclinic space group P2(1)/n and the triclinic space group P1. The former, which is isostructural to C6Cl6, is more common. For molecules that lack inversion symmetry, adoption of this monoclinic structure would necessarily lead to crystallographic disorder. In C6Cl6, the planar molecules form Cl...Cl contacts and also pi...pi stacking interactions. When crystals of C6Cl6 are compressed mechanically along their needle length, that is, [010], a bending deformation takes place, because of the stronger interactions in the stacking direction. Further compression propagates consecutively in a snakelike motion through the crystal, similar to what has been suggested for the motion of dislocations. The bending of C6Cl6 crystals is related to the weakness of the Cl...Cl interactions compared with the stronger pi...pi stacking interactions. The triclinic packing is less common and is restricted to molecules that have a symmetrical (1,3,5- and 2,4,6-) halogen substitution pattern. This packing type is characterised by specific, polarisation-induced X...X interactions that result in threefold-symmetrical X3 synthons, especially when X = I; this leads to a layered pseudohexagonal structure in which successive planar layers are inversion related and stacked so that bumps in one layer fit into the hollows of the next in a space-filling manner. The triclinic crystals shear on application of a mechanical stress only along the plane of deformation. This shearing arises from the sliding of layers against one another. Nonspecificity of the weak interlayer interactions here is demonstrated by the structure of twinned crystals of these compounds. One of the compounds studied (1,3,5-tribromo-2,4,6-triiodobenzene) is dimorphic, adopting both the monoclinic and triclinic structures, and the reasons for polymorphism are suggested. To summarise, both chemical and geometrical models need to be considered for X...X interactions in hexahalogenated benzenes. The X...X interactions in the monoclinic group are nonspecific, whereas in the triclinic group some X...X interactions are anisotropic, chemically specific and crystal-structure directing.     

4-氨基-2,6-二甲基嘧啶的合成结构和光谱性质研究

合成并制备了氨基嘧啶衍生物C₆H₉N₃的单晶体。用X-射线单晶衍射法测定了晶体结构。测定了分子的红外光谱(400-400Ocm^-1)和紫外可见吸收光谱(190-800nm),探讨了溶剂极性的改变对分子光谱性质的影响。     

Crystal and molecular structures of ionophore-siderophore host-guest supramolecular assemblies relevant to molecular recognition

Ionophore-siderophore host-guest assemblies composed of 18-crown-6 and ferrioxamine B, benzo-18-crown-6 and ferrioxamine B, and cis-syn-cis-dicyclohexano-18-crown-6 and ferrioxamine B were successfully crystallized, and their structures were determined by single-crystal X-ray diffraction. All three crystal lattices also include solvated Mg(II) and perchlorate ions. The ionophore-siderophore host-guest assembly is noncovalently held together by a hydrogen bonding interaction between the pendant protonated amine in the second coordination sphere of ferrioxamine B and the hydrogen bond acceptor oxygen atoms in the crown ether. The crystals of 18-crown-6:ferrioxamine B host-guest assembly are monoclinic, with space group P2(1)/c, and four molecules per unit cell with dimensions a = 19.8327(11) A, b = 20.4111(11) A, c = 15.1698(8) A, and beta = 96.435(1) degrees. The crystals of benzo-18-crown-6:ferrioxamine B host-guest assembly are triclinic, with space group P(-)1, and two molecules per unit cell with dimensions a = 11.1747(10) A, b = 16.0580(15) A, c = 18.4175(17) A, alpha = 80.469(3) degrees, beta = 81.481(3) degrees and gamma = 70.212(2) degrees. The crystals of cis-syn-cis-dicyclohexano-18-crown-6:ferrioxamine B host-guest assembly are monoclinic, with space group P2(1)/c, and four molecules per unit cell with dimensions a = 20.1473(13) A, b = 21.5778(15) A, c = 14.8013(10) A, and beta = 94.586(2) degrees. The crystal structures of all three host-guest assemblies contain a racemic mixture of Lambda-N-cis, cis and Delta-N-cis, cis coordination isomers of ferrioxamine B. The crystal structures indicate that the steric rigidity of the benzo-18-crown-6 and cis-syn-cis-dicyclohexano-18-crown-6 cavity has a pronounced effect on the conformation of the crown ring and ultimately on the hydrogen bonding interactions between the crown ethers and ferrioxamine B. The structural parameters and the conformational features of the ferrioxamine B guests compare very well with each other and with those of the ferrioxamine B structure obtained in the absence of a host. Structural features relevant to siderophore molecular recognition are discussed.     

Inherent structures of crystalline tetracene

We have systematically sampled the potential energy surface of crystalline tetracene to identify its local minima. These minima represent all possible stable configurations and constitute the "inherent structures" of the system. The crystal is described in terms of rigid molecules with Coulombic and atom-atom interactions. Hundreds of distinct minima are identified, mostly belonging to the space groups P (triclinic) and P2(1)/c (monoclinic), with a variety of structural arrangements. The deepest minimum corresponds to the high temperature-low pressure polymorph. This is the only polymorph with a completely described X-ray structure, which is satisfactorily described by the calculations. The next deep minimum is likely to correspond to the low temperature-high pressure polymorph, which has been experimentally identified but not yet fully described.     

新型(十)-樟脑酮亚胺的Pd(II)、Co(II)配合物的晶体结构研究

(+)-樟脑与6-甲基-2-氨甲基吡啶缩合得到一种新的手性双齿配体-1,7,7-三甲基-双环[2.2.1]-2-(6'-甲基-2'-氨甲基)吡啶亚胺(1), 与二价钯生成配合物2, 晶体属P21空间群, 晶胞参数为a=10.641(2), b=10.706(2), c=11.011(2)埃; β=115.63(1)°;V=1131.15(40)埃^3; Z=2, 二价钴与1生成配合物3, 晶体属PI空间群, 晶胞参数为a=7.429(2), b=7.971(3), c=16.304(5)埃; a=80.19(3), β=77.10(2), γ=83.21(2)°; V=924.25(56)埃^3; Z=2。根据晶体数据讨论了分子的结构特征, 并对配合物的红外、紫外和核磁共振谱的变化作了解释。     

Absolute helical arrangement of sulfonamide in the crystal

[reaction: see text] 1,2-Bis(N-benzenesulfonyl-N-methylamino)benzene (2), which has no fixed asymmetric element, was crystallized from ethyl acetate as chiral crystals belonging to space group P4(1)2(1)2 (No. 92) or P4(3)2(1)2 (No. 96). The array of molecules built by the CH-pi interaction along the c-axis forms an enantiomeric helical superstructure in each individual crystal. The absolute configurations of the chiral crystals of 2 were determined by X-ray crystal structure analysis using the Flack parameter method. The solid-state CD spectra of the chiral crystals in KBr were mirror images. The equilibrium between the two enantiomers in solution is fast during crystallization at ambient temperature, and the energy barrier (DeltaG()) is estimated to be 11.7 +/- 0.3 kcal/mol (233 K).     

二种新型有侧向取代基液晶化合物结构及性质

用X射线单晶衍射方法测定了液晶化合物2,5-双(4-乙基苯甲酰氯基)苯乙烯(Ⅰ)和2,5-双(4-甲氧基苯甲酰氧基)苯甲醛(Ⅱ)的单晶结构和分子结构. 化合物Ⅰ属三斜晶系, 空间群P(1), 晶胞参数: a=0.9356(6) nm, b=0.9842(6) nm, c=1.3357(8) nm, α=108.68(5)°, β=105.67(5)°, γ=96.36(5)°, Z=2; 化合物Ⅱ属单斜晶系, 空间群P_n, 晶胞参数: a=0.9109(2) nm, b=0.9187(3) nm, c=2.3166(8) nm, β=93.93(2)°, Z=4. 在化合物Ⅰ和Ⅱ晶体中, 分子均呈伸展构象, 分子中的三个苯环平面取向相互成一定的夹角. 分子在晶胞中治其伸展方向相互平行堆积, 相邻分子的侧链基团(乙烯基, 甲醛基)以较短的分子间距0.47-0.56 nm相向排列. 化合物Ⅰ晶胞中分子堆积密度比化合物Ⅱ松散. 晶体结构分析结果合理地解释了化合物Ⅰ的高聚合性.     

Crystal and molecular structure of 3-hydroxy-5-phenylisoxazole (α form)

The crystal structure of the α form of 3-hydroxy-5-phenylisoxazole has been determined from three-dimensional X-ray data. The crystals are monoclinic, space group P2₁/n with four molecules in the unit cell. The cell dimensions are: a = 10.41(2); b = 3.89(1); c = 19.14(4) Å; β = 96.1° (3). The structure was refined by the block-diagonal least-squares method to a final R value of 0.080 for 1111 observed reflections. The molecular dimensions are in good overall agreement with those in β form, while the packing is markedly different. Conjugation and planarity in the molecule are discussed.     

Structural studies of metabolic products of dopamine. III. Crystal and molecular structure of (--)-adrenaline.

The crystal structure of (--)-adrenaline has been determined by X-ray methods, using 831 observed reflections collected by counter methods. The crystals are monoclinic, space group P2-1 with a=7.873(2), b=6.790(2), c=8.638(2) A and beta=98.01(2) degrees. Least-squares refinements yielded a conventional R-factor of 0.053. Standard deviations in bond lengths are 0.005-0.006 A and in bond lengths aree 0.005-0.006 A and in bond angles 0.4 degrees. The adrenaline molecules were found to exist as zwitterions in the crystals. The conformation of the adrenaline molecule corresponds closely to that usually encountered among the salts of the sympathomimetic amines. The crystals consist of molecular double layers parallel to (100). The molecules within a layer are linked through hydrogen bonds of the types N--H...O and O--H...O, whereas the layers are connected by van der Waals interactions.