Nano-objects - sculpting and shape in molecular material design (The Pierre Gilles de Gennes ILCS prize lecture)

ABSTRACT

Early liquid crystal compounds often had relatively simple molecular structures, but with the invention of electro-optical devices, the design of materials became increasingly important. Property-structure correlations have promoted computer-aided rational design to the point where it is becoming a necessity in the selection of compounds for preparation. For simple molecular architectures, allowable electrostatic interactions in the face of steric repulsion were used in a phenomenological way to generate new mesophases, such as the hexatic phase, and to engineer materials with desirable physical properties. Materials chemists, in the creation of substances of greater complexity, have built upon these forms of research. Interestingly, the larger the system often the more simply it becomes as the molecular bulk and shape begin to dominate over the surface interactions. Nano-objects of unique shapes, such as ‘Janus’ grains, created in the process of design can kindle the formation of new mesophases, such as the twist-bend and splay phases generated through the crowding of molecular particles, and minimisation of the free volume. This article explores the development of the shapes of molecular grains and the mesophases they spawn.     

C3N6H6(H3BO3)2的合成及晶体结构

以三聚氰胺和硼酸为原料在水溶液中反应合成出了一种新的BCN化合物先驱体C3N6H6(H3BO3)2。XRD表征结果表明三聚氰胺和硼酸的最佳配比为1∶3(物质的量比)。用单晶X-射线衍射分析法测定了该化合物的晶体结构。该化合物属单斜晶系,空间群为P21/C,晶胞参数为a=0.3597(7)nm,b=2.0105(4)nm,c=1.4112(3)nm,α=90,°β=92.07(3),°γ=90,°V=1.0199(3)nm3,Z=4,D c=1.627g.cm-3,μ(MoKα)=0.144mm-1,F(000)=520。晶体结构经全矩阵最小二乘法修正,最终可靠因子R1=0.0519,wR2=0.1361。该化合物是由C3N6H6分子和H3BO3分子通过氢键加合组装形成的三维超分子结构化合物。     

超分子化合物[Ni(C_6H_4O_2N)_2·(H_2O)_4]_n的水热合成及晶体结构

用皮考林酸和六水合氯化镍反应制备了一种三维氢键超分子配合物,经X射线衍射分析确定了单晶结构.该晶体属单斜晶系,P21/m空间群,晶胞参数为:a=0.976 0(2)nm,b=0.522 54(10)nm,c=1.450 1(3)nm,Mr=374.98,α=90.08(3)°,β=90.08(3)°,γ=90°,V=0.739 63(3)nm3,Z=2,ρ=1.684 g/cm3,F(000)=388,μ=1.357 mm-1,R=0.039 0,wR=0.090 8.共收集2 656个衍射数据,其中1 569个为独立衍射点(Rint=0.033 2),可观测点数1 382个(I>2σ(I)).结果表明,在组成该超分子体系的基本结构单元[N i(C6H4O2N)2.(H2O)4]中,N i(Ⅱ)离子形成六配位的稍拉长的八面体构型,配合物单元之间通过氢键相互连接,形成了无限延伸的具有网状结构的三维超分子体系.     

Ab initio investigation of the Young's modulus of polyamide‐6

The Young's modulus of the α form of polyamide‐6 has been calculated using the supermolecule model. The crystalline polymer was represented by a single‐chain molecule, divided into a head, body, and tail part. The body of the model contains an even number of polyamide‐6 units (4–16 units) and is representative for a polyamide‐6 chain. The periodicity of the system was not explicitly taken into account, but in a few tests the effect of a linear constraint has been evaluated. An n‐butyl and n‐pentyl group have been used as head and tail, respectively. In a number of additional calculations the length of the head and tail has been varied. For all supermolecule models the equilibrium and elongated structures have been optimized using ab initio Hartree–Fock calculations with a 6‐31G** basis set. From the energy values of the optimized structure a Young's modulus of 334 GPa has been extrapolated for both the unconstrained and linearly constrained models. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Study on the inclusion compound of β-cyclodextrin with (η5-cyclopentadienyl)tricarbonylmanganese(0)

The supramolecular inclusion compound of β-cyclodextrin (β-CD, host) with (η5-cyclopentadienyl)tricarbonylmanganese [MnCp(CO)3, guest] was obtained in a crystalline state. The host-guest compound is thermally stable and do not liberate the guest on heating at 100$ in vacuum. It was characteried by elemental analysis,1H NMR, differential scanning thermal (DSC) analysis and TLC. Continueous variation plot by NMR method shows that β-CD formed 1:1 inclusion compound with MnCp(CO)3. On the basis of 1H NMR spectra and the model building with Corey Pauling Koltum (CPK) models, the most probable inclusion mode is proposed.     

蒽基修饰的新型铂基大环化合物的合成

以3,5-二溴苯甲醚为起始原料,通过Suzuki偶联反应制得3,5-二吡啶苯甲醚(3); 3经三溴化硼脱保护得到3,5-二吡啶苯酚(4); 4进一步发生亲核取代反应得到化合物5;化合物6与5组装得到新型铂基超分子大环,其结构经¹H NMR和³¹P NMR表征。     

Alkaline hydrolysis of ethylene phosphate: an ab initio study by supermolecule model and polarizable continuum approach

The alkaline hydrolysis reaction of ethylene phosphate (EP) has been investigated using a supermolecule model, in which several explicit water molecules are included. The structures and single-point energies for all of the stationary points are calculated in the gas phase and in solution at the B3LYP/6-31++G(df,p) and MP2/6-311++G(df,2p) levels. The effect of water bulk solvent is introduced by the polarizable continuum model (PCM). Water attack and hydroxide attack pathways are taken into account for the alkaline hydrolysis of EP. An associative mechanism is observed for both of the two pathways with a kinetically insignificant intermediate. The water attack pathway involves a water molecule attacking and a proton transfer from the attacking water to the hydroxide in the first step, followed by an endocyclic bond cleavage to the leaving group. While in the first step of the hydroxide attack pathway the nucleophile is the hydroxide anion. The calculated barriers in aqueous solution for the water attack and hydroxide attack pathways are all about 22 kcal/mol. The excellent agreement between the calculated and observed values demonstrates that both of the two pathways are possible for the alkaline hydrolysis of EP.     

超分子化学药物研究

超分子药物化学是超分子化学在药学领域的新发展．该领域研究活跃,发展迅速,是一个充满活力的新兴交叉学科领域,并正在逐渐变成一个相对独立的研究领域．迄今已有许多两个或两个以上分子通过非共价键力形成的超分子化学药物应用于临床．超分子化学药物可具有良好的安全性、低毒性、不良反应少、高生物利用度、药物靶向性强、多药耐药性小、生物相容性好、高疗效以及其开发成本低、周期短、成功可能性大等诸多优点而备受关注,显示出超分子化学药物具有很大的发展潜力．本文首次给出了超分子药物的定义．结合自己的工作,参考国内外文献综述了超分子化学药物在抗肿瘤、抗炎镇痛、抗疟、抗菌、抗真菌、抗结核、抗病毒、抗癫痫、作为心血管和磁共振成像药物等医药领域的研究与开发状况,并展望其发展趋势与应用前景．     

氢键在现代化学中的作用

在各种分子间相互作用中,氢键占有很特殊的地位,被称作为超分子化学中的万能相互作用。讨论了氢键在超分子、自组装、分子识别、晶体工程、材料化学和催化过程等现代化学领域中的作用。