Star-Shaped Ruthenium Complexes as Prototypes of Molecular Gears

The design and synthesis of two families of molecular-gear prototypes is reported, with the aim of assembling them into trains of gears on a surface and ultimately achieving controlled intermolecular gearing motion. These piano-stool ruthenium complexes incorporate a hydrotris(indazolyl)borate moiety as tripodal rotation axle and a pentaarylcyclopentadienyl ligand as star-shaped cogwheel, equipped with five teeth ranging from pseudo-1D aryl groups to large planar 2D paddles. A divergent synthetic approach was followed, starting from a pentakis(p-bromophenyl)cyclopentadienyl ruthenium(II) complex as key precursor or from its iodinated counterpart, obtained by copper-catalyzed aromatic Br/I exchange. Subsequent fivefold cross-coupling reactions with various partners allowed high structural diversity to be reached and yielded molecular-gear prototypes with aryl-, carbazole-, BODIPY- and porphyrin-derived teeth of increasing size and length.     

新型复合分子筛的合成和催化应用

 系统地归纳总结了最近几年引起人们广泛关注的复合分子筛的研究进展,包括微孔-微孔复合分子筛、微孔-介孔复合分子筛、微孔-大孔复合分子筛及微孔-介孔-大孔复合分子筛的合成和应用近况. 并对复合分子筛的发展前景进行了展望.     

Walking molecules

Movement is intrinsic to life. Biologists have established that most forms of directed nanoscopic, microscopic and, ultimately, macroscopic movements are powered by molecular motors from the dynein, myosin and kinesin superfamilies. These motor proteins literally walk, step by step, along polymeric filaments, carrying out essential tasks such as organelle transport. In the last few years biological molecular walkers have inspired the development of artificial systems that mimic aspects of their dynamics. Several DNA-based molecular walkers have been synthesised and shown to walk directionally along a track upon sequential addition of appropriate chemical fuels. In other studies, autonomous operation--i.e. DNA-walker migration that continues as long as a complex DNA fuel is present--has been demonstrated and sophisticated tasks performed, such as moving gold nanoparticles from place-to-place and assistance in sequential chemical synthesis. Small-molecule systems, an order of magnitude smaller in each dimension and 1000× smaller in molecular weight than biological motor proteins or the walker systems constructed from DNA, have also been designed and operated such that molecular fragments can be progressively transported directionally along short molecular tracks. The small-molecule systems can be powered by light or chemical fuels. In this critical review the biological motor proteins from the kinesin, myosin and dynein families are analysed as systems from which the designers of synthetic systems can learn, ratchet concepts for transporting Brownian substrates are discussed as the mechanisms by which molecular motors need to operate, and the progress made with synthetic DNA and small-molecule walker systems reviewed (142 references).     

B(13) (+) : a photodriven molecular wankel engine

Revved-up rotary: A molecular Wankel motor, the dual-ring structure B(13) (+) , is driven by circularly-polarized infrared electromagnetic radiation. Calculations show that this illumination leads to a guided unidirectional rotation of the outer ring, which is achieved with rotational frequency of the order of 300?GHz.     

Artificial Supramolecular Pumps Powered by Light

The development of artificial nanoscale motors that can use energy from a source to perform tasks requires systems capable of performing directionally controlled molecular movements and operating away from chemical equilibrium. Here, the design, synthesis and properties of pseudorotaxanes are described, in which a photon input triggers the unidirectional motion of a macrocyclic ring with respect to a non-symmetric molecular axle. The photoinduced energy ratcheting at the basis of the pumping mechanism is validated by measuring the relevant thermodynamic and kinetic parameters. Owing to the photochemical behavior of the azobenzene moiety embedded in the axle, the pump can repeat its operation cycle autonomously under continuous illumination. NMR spectroscopy was used to observe the dissipative non-equilibrium state generated in situ by light irradiation. We also show that fine changes in the axle structure lead to an improvement in the performance of the motor. Such results highlight the modularity and versatility of this minimalist pump design, which provides facile access to dynamic systems that operate under photoinduced non-equilibrium regimes.     

Mechanical properties of single motor molecules studied by three-dimensional thermal force probing in optical tweezers.

A new method combining three-dimensional (3D) force measurements in an optical trap with the analysis of thermally induced (Brownian) position fluctuations of a trapped probe was used to investigate the mechanical properties of a single molecule, the molecular motor kinesin. One kinesin molecule attached to the probe was bound in a rigorlike state to one microtubule. The optical trap was kept weak to measure the thermal forces acting on the probe, which were mainly counterbalanced by the kinesin tether. The stiffness of kinesin during stretching and compression with respect to its backbone axis were measured. Our results indicate that a section of kinesin close to the motor domain is the dominating element in the flexibility of the motor structure. The experiments demonstrate the power of 3D thermal fluctuation analysis to characterize mechanical properties of individual motor proteins and indicate its usefulness to study single molecule in general     

离子热合成磷铝分子筛

AlPO-11 molecular sieve with AEL structure was ionothermally synthesized using ionic liquid solvent as medium. The effects of ionic liquid amount, synthesis time and temperature were investigated. The structure and characteristics of molecular sieve samples were characterized by X-ray diffraction(XRD)，scanning electron microscopy (SEM), thermo gravimetric analysis(TGA). The results indicate that AlPO-11 molecular sieve could be synthesized by 1-ethyl-3-methylimidazolium bromide ([Emim]Br) ionic liquid as both the solvent and template.     

四烷基间苯二酚杯芳烃八[N-(2-吡啶甲基)乙酰胺]的合成和分子结构

为深入开展杯芳烃为骨架的超分子拓扑结构的组装和性能,开展了间苯二酚杯芳烃八取代吡啶酰胺的合成和分子结构的研究。 以四丙基、四己基和四庚基间苯二酚杯芳烃为原料,使用α-氯乙酸甲酯实现O-烃基化,后者在无溶剂条件下与2-氨甲基吡啶反应实现酰胺化,制备了烷基间苯二酚杯芳烃八[N-(2-吡啶甲基)乙酰胺]衍生物。 用X衍射方法测定了四丙基间苯二酚杯芳烃八乙酸甲酯、四丙基以及四己基间苯二酚杯芳烃八[N-(2-吡啶甲基)乙酰胺]的单晶分子结构。 在晶体中,间苯二酚杯芳烃都以全顺式构型存在,在成环的四个间苯二酚单元中,1,3-位的两个间苯二酚单元处于近直立构象,2,4-位的另两个间苯二酚单元处于近平伏构象,而4个烷基皆处于分子的下缘,8个乙酰胺支链伸向分子的外围。     

金属磷铝(MeAPO)分子筛的合成及催化活性

本文用水热法合成了MAPO-5、CoAPO-5、CoMAPO及MAPO-36四种分子筛。对新合成的样品进行了XRD、IR、SEM及原子吸收光谱分析。确认各样品皆为分子筛结构,初步证实金属Mg和(或)金属Co进入到分子筛的结构骨架。金屑磷铝分子筛比磷铝分子筛裂化活性提高很大,从分析产物C_3及C_4看出各样品的低催化活性对应于低的C_4/C_3·C_4/C_3值反映了分子筛的窄小空腔或弯曲通道。     

VEGFR-2 与抑制剂Sunitinib 的分子对接及分子动力学研究

用分子对接方法研究了VEGFR-2 和抑制剂Sunitinib 的相互作用模式, 并对其复合物进行了10 ns 的分子动力学(Molecular Dynamics, MD)模拟. 结果表明, 抑制剂Sunitinib 能与VEGFR-2 中位于活性空腔的Glu885, Ile888, His1026,Asp1028, Asp1046 五个氨基酸残基形成疏水作用; 另外, VEGFR-2 中His1026, Cys1024, Asp1046 三个氨基酸残基能与Sunitinib 形成三个作用强度不同的氢键. 这些基团之间的相互作用是Sunitinib 抑制VEGFR-2 活性的关键因素. 研究结果可为VEGFR-2 抑制剂的结构改良、分子设计、合成提供理论参考, 并有助于寻找活性更高、效果更好的抗肿瘤药物.     

Theoretical investigation on the transportation behavior of molecular wires with redox reaction

A series of model molecules [sequential quinone (Q) or hydroquinone (HQ) rings connected by triple bonds] as molecular wires have been investigated by using density functional theory combined with nonequilibrium Green's function method. The results show that the system has two discrete conductance states: a low-conductance state with Q form, and a high-conductance state with HQ form. The systematic investigations have suggested that more Q/HQ pairs in the system may improve the on/off ratio, though long molecule reduces the conductance of the molecular junction. The switch mechanism has been explained via molecular electronic structure as well as transmission spectra.     

Synthesis and X-ray Crystal Structure of a New Molecular Clip

The synthesis and X-ray crystal structure of a new molecular clip 2 was reported. It （C24H24N4O2, Mr = 400.47） crystallizes in the space group C2/c with a = 15.587（2）, b = 8.5805（12）, c = 15.259（2） A, β = 102.448（3）°, V= 1992.9 （5）A63, Z = 4, Dc = 1.335 g/cm63,μ = 0.087 mm^-1 and F（000） = 848. It remains monomeric in the crystal and a tape-like structure is formed in the crystal structure of molecular clip. The most unusual structural feature of 2 is the boat conformation of its cyclohexyl ring imposed by the ring fusion at C（9）-C（9a）.     

Simple and effective one‐pot synthesis of (meth)acrylic block copolymers through atom transfer radical polymerization

The synthesis of di‐ and triblock copolymers using atom transfer radical polymerization (ATRP) of n‐butyl acrylate (BA) and methyl methacrylate (MMA) is reported. In particular, synthetic procedures that allow for an easy and convenient synthesis of such block copolymers were developed by using CuBr and CuCl salts complexed with linear amines. Polymerizations were successfully conducted where the monomers were added to the reactor in a sequential manner. Poor cross‐propagation between poly(n‐butyl acrylate) (PBA) macroinitiators and MMA was minimized, and therefore control of molecular weights and distributions was realized, by using halogen exchange—a technique involving the addition of CuCl to the MMA during the chain extension of the PBA macroinitiator. High molecular weight (M_n ∼ 90,000) and low polydispersity (M_w /M_n < 1.35) ABA triblock copolymers were also prepared and their structure and properties in bulk have been preliminary characterized indicating the potential of ATRP for the production of all‐acrylic thermoplastic elastomers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2023–2031, 2000     

An expedient one-pot sequential five-component synthesis of highly substituted spiro-pyrrolidine heterocycles

An expedient one-pot sequential five-component synthesis of highly substituted pyrrolidine heterocycles involving [3+2]-cycloaddition of azomethine ylides as the key step is described. The protocol provides a mild reaction condition, high yield of the products, high regioselectivity and operational simplicity to assemble complex structural entity in a single operation. The structure of the product was confirmed by spectroscopic and single crystal X-ray analysis.     

A Claisen rearrangement route to the vineomycins

Anthrarufin is converted by a high yield route involving sequential Claisen rearrangements to an intermediate (3) suitable for the synthesis of vineomycins     

Molecular Engineering of Metal Alkoxides for Solution Phase Synthesis of High-Tech Metal Oxide Nanomaterials

The ‘bottom-up’ synthesis of inorganic nanomaterials with precision at the atomic/molecular level offers many opportunities for the design and improvement of the nanomaterials for various applications. Molecular engineering during soft chemical processing for the synthesis of functional nanomaterials enables the desired chemical and physical properties of the precursors, such as solubility or volatility, clean decomposition, control of stoichiometry for multimetallic species to name a few, and leads to easy control of uniform particle size distribution, stoichiometry…. This Minireview illustrates some important aspects of the molecular engineering in light of some recent developments from the molecular synthesis of nanomaterials involving non-silicon metal alkoxide systems for high-tech applications.     

Discrete π Stack of a Tweezer-Shaped Naphthalenediimide–Anthracene Conjugate

The design and synthesis of a tweezer-shaped naphthalenediimide (NDI)–anthracene conjugate ( 2NDI ) are reported. In the structure of the closed form (π_NDI ⋅⋅⋅ π_NDI stack) of 2NDI , which was elucidated by single-crystal XRD, the existence of C−H ⋅⋅⋅ O hydrogen bonding involving the nearest carbonyl oxygen atom of an NDI unit was suggested. The tunability of π_NDI ⋅⋅⋅ π_NDI interactions was studied by means of UV/Vis absorption, fluorescence and NMR spectroscopy and molecular modelling. This revealed that the π_NDI ⋅⋅⋅ π_NDI interactions in 2NDI affect the absorption and emission properties depending on the temperature. Furthermore, in polar solvents, 2NDI prefers the stronger π_NDI ⋅⋅⋅ π_NDI stack, whereas the π_NDI ⋅⋅⋅ π_NDI interaction is diminished in nonpolar solvents. Importantly, the conformational variations of 2NDI can be reversibly switched by variation in temperature, and this suggests potential application for fluorogenic molecular switches upon temperature changes.     

Effect of charge-transfer enhancement on the efficiency and rotary mechanism of an oxindole-based molecular motor

Harvesting energy and converting it into mechanical motion forms the basis for both natural and artificial molecular motors. Overcrowded alkene-based light-driven rotary motors are powered through sequential photochemical and thermal steps. The thermal helix inversion steps are well characterised and can be manipulated through adjustment of the chemical structure, however, the insights into the photochemical isomerisation steps still remain elusive. Here we report a novel oxindole-based molecular motor featuring pronounced electronic push–pull character and a four-fold increase of the photoisomerization quantum yield in comparison to previous motors of its class. A multidisciplinary approach including synthesis, steady-state and transient absorption spectroscopies, and electronic structure modelling was implemented to elucidate the excited state dynamics and rotary mechanism. We conclude that the charge-transfer character of the excited state diminishes the degree of pyramidalisation at the alkene bond during isomerisation, such that the rotational properties of this oxindole-based motor stand in between the precessional motion of fluorene-based molecular motors and the axial motion of biomimetic photoswitches.

A novel oxindole-based light-driven molecular motor with pronounced push–pull character was investigated. The rotary mechanism stands in between the precessional motion of fluorene-based motors and the axial motion of biomimetic photoswitches.     

中孔分子筛MCM-41的合成与表征

以白炭黑和正硅酸乙酯为硅源,十二、十六烷基三甲基铵为模板剂,用水热法和室温直接法合成出中孔分子筛MCM-41,考察了对合成的影响因素,用红外光谱、吸附、孔分布、热分析等手段对这两种产物进行了表征。结果表明:这种分子筛可以在很宽的配比范围内获得,但较高水硅比更有利于合成;在水硅比较低的体系中得到了一种类MCM-41中孔相(亦应属于MCM-41),其XRD衍射峰较宽,2θ角度偏低,具有类似于无定形硅铝酸盐的骨架结构。     

Oxoanion binding by guanidiniocarbonylpyrrole cations in water: a combined DFT and MD investigation

Structures and properties of nonbonding interactions involving guanidinium-functionalized hosts and carboxylate substrates were investigated by a combination of ab initio and molecular dynamics approaches. The systems under study are on one hand intended to be a model of the arginine-anion bond, so often observed in proteins and nucleic acids, and on the other to provide an opportunity to investigate the influence of molecular structure on the formation of supramolecular complexes in detail. Use of DFT calculations, including extended basis sets and implicit water treatment, allowed us to determine minimum-energy structures and binding enthalpies that compared well with experimental data. Intermolecular forces were found to be mostly due to electrostatic interactions through three hydrogen bonds, one of which is bifurcate, and are sufficiently strong to induce a conformational change in the ligand consisting of a rotation of about 180 degrees around the guanidiniocarbonylpyrrole axis. Free binding energies of the complexes were evaluated through MD simulations performed in the presence of explicit water molecules by use of the molecular mechanics Poisson-Boltzmann solvent accessible surface area (MM-PBSA) and linear interaction energy (LIE) approaches. LIE energies were in quantitative agreement with experimental data. A detailed analysis of the MD simulations revealed that the complexes cannot be described in terms of a single binding structure, but that they are characterized by a significant internal mobility responsible for several low-energy metastable structures.