配合物[Ni(qina)_2(H_2O)_2]的合成及结构

近年来,晶体分子结构在设计和组装各种光、电磁离子交换、催化等新型功能材料方面受到广泛关注[1-5].在分子体系形成的过程中,配位键构成分子主体,而氢键、π-π堆积和金属-金属等弱相互作用则是分子之间构筑成超分子结构的稳定因素[6-8].喹哪啶酸(qina)具有鳌合配位能力和疏水性能,其配合物往往通过π-π堆积形成超分子化合物[9].     

从单分子到分子聚集态科学

有机光电功能材料的宏观性能不仅只依赖于基元分子自身的理化性质,还取决于其分子聚集行为和聚集态结构。在特定的聚集态结构中,分子间弱相互作用的加和与协同,可促进体系性能的拓展与质变,获得超越分子本征属性的功能。这凸显出当前化学研究逐步从关注单分子向分子聚集态科学转变,体现出分子聚集态研究的重要性。本文借助有机室温磷光性能对分子聚集态结构的高度灵敏性与响应性,系统探讨了分子聚集态结构的形成规律与核心影响因素。以此为基础,进一步拓展分子聚集态研究的应用领域,包括力致发光、有机二阶非线性光学、力致变色、有机发光二极管等,从静态调控到动态刺激响应(刺激源:力、热、光、电场等),从单一结构到多组分体系与器件,同时,确立了各种有机光功能材料的优势分子聚集形式,提出了聚集态调控的有效策略与研究思路,阐述了光电功能材料体系设计与合成的可控性与预见性。     

有机非线性光学晶体NPP的AFM研究

有机二阶非线性光学活性晶体的分子设计和晶体工程是复杂而又引人注目的课题．有机非线性光学晶体N一忡硝基苯基）－LWe脯氨醇（NPP）是一个极为成功的自］子山．由于在＊＊P分子中引入了含手性碳原子和可形成分子间氢键的电子给体脯氨醇，使得其分子跃迁偶极矩与单科P21晶体结构的二重轴之间的夹角为586”．接近于理论优化值（54．74”），因此，＊＊P具有很高的宏观二阶非线性光学活性，其粉末二次谐波强度为尿素的150倍．自1984年首次报导以来，对它的晶体生长门和物理性质已进行了广泛深入的研究．原子力显微镜（＊＊M）能够以极高…     

几种查耳酮的二阶非线性光学性质解析

合成了一系列的查耳酮衍生物,系统地测量了其ＳＨＧ（二次谐波产生）效率和截止吸以长,并用ＣＮＤＯ／Ｓ－ＣＩ方法计算了它们的二阶非线性光学系数β值。通过对这些化合物性质的分析发现：（１）取代基Ｂｒ不仅能有效地增强微观非线性能能有效地增强材料的宏观非线性效应。（２）取代基Ｂｒ有利于改善材料的透光性能的和热稳定性;（３）分子在晶体中的空间取向是影响材料宏观非线性的另一个重要因素。     

非线性光学材料的设计

本文在理论与实践、微观与宏观基础上,用分子工程和晶体工程手段对非线性光学材料的优化和筛选进行了系统的设计。对目前研究活跃被认为有前途的非线性光学材料进行了归纳和总结。     

柔性二元羧酸桥联双核镉(Ⅱ)配合物的合成及晶体结构研究

晶体工程是根据分子堆积和分子间的相互作用,将超分子化学的原理、方法以及控制分子间作用的策略用于晶体,以设计出结构新颖、具有独特的物理性质和化学性质的新晶体。超分子间的非共价作用主要包括氢键、π-π堆积作用、阳离子-π作用和疏水缔合等,通过选择不同结构的配体,使其在配合物中产生多种非共价作用,是实现从分子到材料的一条重要途径。     

有机非线性光学晶体N-(4-硝基苯基)-L-脯氨醇(NPP)表面结构的AFM研究

本文首次用AFM对非线性晶体的表面结构进行了研究。NPP晶体属单斜晶系,其表面结构与晶面有密切关系。用AFM对其解理(101)面和(001)的研究表明,这两个表面上的分子排列与体相结构一致,未发生重构;在(001)面上分子中的苯环和五元环可被区分开来。用AFM所测得的分子跃迁偶极矩与单斜P2_1晶体结构的二重轴之间的夹角为56°,接近理论值,说明NPP晶体具有很高的宏观二阶非线性活性。这些结果首次在实空间中直接给出了NPP晶体不同晶向的表面结构。     

非线性光学有机晶体材料的研究进展

随着科技的进步和时代的发展,光电子技术将是21世纪的核心技术之一.对于光电子技术的发展,非线性光学材料,尤其是非线性光学晶体是不可缺少的关键材料.本文主要从分子设计方面概述了阴阳离子二元生色团体系、纯有机分子、纳米晶体和有机金属复合物等几种主要的非线性光学有机晶体材料的研究情况,并对其各自的特点做了简单的说明.     

分子手性的温度效应：D-丙氨酸的变温X衍射和中子衍射研究

利用X衍射（300, 270, 250 K）和中子衍射（300, 260, 250, 240 K）研究D-氨酸单晶在静态的和动力学的变温过程中的结构特征以及考证Salam预言的由D到L构型转变的可能性. 实验发现丙氨酸晶体的空间群P212121对称性没有改变. 实验结果否定了构型相变的可能，但是发现在~250 K有一个微小的、连续的对称性破缺发生. 晶体分子振动产生的环电流模型可以用来解释D-和L-丙氨酸单晶直流磁化率和天然旋光角相反的现象， 与之相关的中子衍射数据进一步揭示了变温过程中αC－H(2), N－H(1), N－H(4), N－H(6) 键长的不同变化. 中子衍射还显示了质子移动所导致的动力学无序，来源于分子内氨基和羧基形成的氢键和分子间αC－H和氨基形成的氢键，从而产生的晶格扭曲和NH³⁺的扭转. 实验结果表明Salam预言相变不是传统意义的结构相变，而是由于温度效应导致了在相变点附近分子的宇称破缺能差（PVED）增大，然后通过氨基酸分子的隧道效应扩大了宇称破缺能差的影响，这一研究为生命现象中快速的均一手性形成提供了非线性机理的合理解释.     

尿素分子团簇线性和一阶非线性光学极化率的理论计算

检验分子晶体非线性光学极化率的可加性,对于确认有向气体模型(Oriented-Gas Model) 具有重要的科学意义,对探索新型实用的分子非线性光学材料也有实际的意义。本文对尿素晶体中分子簇非线性光学极化率的可加性做了详尽的理论研究。首次做到了尿素分子最近邻排布团簇的非线性光学极化率的从头算,从而扩展了前人的工作。研究结果有效地确认了有向气体模型。同时,我们还提出了壳层结构模型 (Shell-Structure Model),用以解决有向气体模型中的缺陷,可实现更为有效可靠地计算晶体宏观非线性光学系数。     

Structure of bilirubin and its anion according to quantum chemical calculations and molecular dynamics simulation

Quantum chemical calculations of the structural characteristics of the bilirubin molecule and its anion are performed. Intramolecular hydrogen bonds are studied using NBO analysis. It is shown that hydrogen bonds in the bilirubin molecule are nonequivalent, and the bond formed by the keto oxygen of the pyrrole ring and the hydrogen of the carboxyl group belonging to the propionate residue is energetically more favorable. Structural characteristics of the molecular and ion forms of bilirubin in aqueous solution are studied by molecular dynamics simulation. It is found that intermolecular hydrogen bonds with water molecules are formed due to oxygen atoms of the carboxyl group and the keto group of bilirubin, and the probability of their formation by anions is much higher than that for molecules.     

Structure and dynamics of methanol in water: a quantum mechanical charge field molecular dynamics study

An ab initio quantum mechanical charge field molecular dynamics simulation was carried out for one methanol molecule in water to analyze the structure and dynamics of hydrophobic and hydrophilic groups. It is found that water molecules around the methyl group form a cage-like structure whereas the hydroxyl group acts as both hydrogen bond donor and acceptor, thus forming several hydrogen bonds with water molecules. The dynamic analyses correlate well with the structural data, evaluated by means of radial distribution functions, angular distribution functions, and coordination number distributions. The overall ligand mean residence time, τ identifies the methanol molecule as structure maker. The relative dynamics data of hydrogen bonds between hydroxyl of methanol and water molecules prove the existence of both strong and weak hydrogen bonds. The results obtained from the simulation are in excellent agreement with the experimental results for dilute solution of CH(3)OH in water. The overall hydration shell of methanol consists in average of 18 water molecules out of which three are hydrogen bonded.     

单笼形水分子簇中心水分子对类型关系

随机产生单笼形水分子簇(H2O)n(n=8~36),经分类统计后发现,在笼形水分子簇中,其1221,1212,2121和2112四类氢键的个数与水分子和氢键总数之间有定量关系,且1212类氢键的个数与2121类的氢键始终相等.如果笼形水分子簇中某一类氢键数已知,则它的其余三类氢键的个数也随即确定.     

Intra- and intermolecular hydrogen bonding in 3-hydroxy- and 5-hydroxychromone

The crystal structures for 3-hydroxychromone and 5-hydroxychromone have been obtained. Both molecules exhibit intramolecular hydrogen bonding between the hydroxy group and the ketone oxygen atom. However, only the 3-hydroxy derivative contains hydrogen bonds between molecules. By comparing the current results with those obtained for the corresponding flavone derivatives, the effect of the B phenyl group on hydrogen bonding is inferred.     

Biodegradable gemini surfactants. Correlation of area per surfactant molecule with surfactant structure

Values of the area per surfactant molecule of various single chain and gemini quaternary ammonium surfactants containing biodegradable amide and ester groups are obtained from the surface tension measurements and they are mutually compared. It was found that surfactant molecules with the ester group in their structure occupy smaller area at the air/water interface than the corresponding molecules with the amide group, mainly due to the higher conformational flexibility of ester groups. In decreasing the area per surfactant molecule value, hydrogen bonding (both inter- and intramolecular) plays a significant role when amide groups are present in the spacer of a gemini molecule. They must be separated by a polymethylene chain or a flexible group such as cyclohexane which is short enough to allow intramolecular hydrogen bonds. The flexible cyclohexane group with the amide group in single chain surfactants may lead to the formation of intermolecular hydrogen bonds among surfactant molecules which also results in the reduction of the area per surfactant molecule.     

IR investigation of hydrogen bonds in weakly hydrated films of poly(vinyl alcohol)

A system of hydrogen bonds in weakly hydrated PVA films containing up to ≤8.5 wt % water is investigated via IR spectroscopy. It is shown that water molecules bind to only part of the hydroxyl groups of the polymer that are available for hydration and form the first hydrating layer. In a completely dehydrated film, practically every hydroxyl group of PVA forms hydrogen bonds with two other hydroxyl groups and serves as both a proton donor and a proton acceptor. In the hydrated film, one to three water molecules directly bind with one hydroxyl group of PVA.     

Urea Derivatives as Functional Molecules: Supramolecular Capsules,Supramolecular Polymers,Supramolecular Gels,Artificial Hosts,and Catalysts

Urea, which has both hydrogen bond acceptor and donor moieties, is an ideal structure for a supramolecular synthon. Various supramolecules having ureido group(s) have been widely developed. This article summarizes recent developments of urea derivatives that exhibit various functions: i) supramolecular capsules that form discrete urea–urea intermolecular hydrogen bonds, ii) supramolecular polymers that form continuous urea–urea intermolecular hydrogen bonds, iii) supramolecular gels that form continuous urea–urea intermolecular hydrogen bonds, iv) artificial host molecules based on the molecular recognition ability of the ureido group, and v) catalytic reactions developed by utilizing the molecular recognition ability of the ureido group.     

Interaction configurations of H2O molecules in a protein (Stratum Corneum) by infrared spectrometry

The procedure previously used to determine the interaction configurations of H₂O molecules in various polysaccharides is applied to a protein: Stratum Corneum (SC). It consists of following by infrared (IR) spectrometry the evaporation, heating and addition of water to a SC membrane. Analyses of the spectra corresponding to these experiments show that even H₂O molecules in equilibrium with the atmosphere are inserted in the protein itself and are held by one hydrogen bond which they accept from an N---H group of the protein and at least one hydrogen bond which they establish (donate) on a C=O group of the protein. At higher concentrations of water, H₂O molecules aggregate and form microdroplets embedded in the protein. Addition of water followed by evaporation of the added H₂O molecules results in an enhancement of the number of hydrogen bonds of type N---HO=C inside the protein. It makes water molecules appear as catalysts to rebuild hydrogen bonds in the protein.     

Liquid structure of acetic acid-water and trifluoroacetic acid-water mixtures studied by large-angle X-ray scattering and NMR

The structures of acetic acid (AA), trifluoroacetic acid (TFA), and their aqueous mixtures over the entire range of acid mole fraction xA have been investigated by using large-angle X-ray scattering (LAXS) and NMR techniques. The results from the LAXS experiments have shown that acetic acid molecules mainly form a chain structure via hydrogen bonding in the pure liquid. In acetic acid-water mixtures hydrogen bonds of acetic acid-water and water-water gradually increase with decreasing xA, while the chain structure of acetic acid molecules is moderately ruptured. Hydrogen bonds among water molecules are remarkably formed in acetic acid-water mixtures at xA相似文献   

Structures of N—（2,3,4,6—Tetra—O—acetyl—β—D—glycosyl） thiocarbamic Benzoyl Hydrazine

The crystal structure of N-(2,3,4,6-tetra-O-acetyl-β-D-gly-cosyl)-thiocarbamic benzoyl hydrazine(C22H27N3O9S) was determined by X-ray diffracton method.The hexopyranosyl ring adopts a chair conformation.All the ring substituents are in the equatorial positions.The acetoxyl-methyl group is in synclinal conformation.The S atom is in synperiplanar conformation while the benzoyl hydrazine moiety is anti-periplanar.The thiocarbamic moiety is almost companar with the benzoyl hydrazine group.There are two intramolecular hydrogen bonds and one intermolecular hydrogen bond for each molecule in the crystal structure.The molecules form a network structure through intermolecular hydrogen bonds.