Stereoisomeric Doubly Interpenetrating Three-Dimensional Networks of Tripodal Neodymium(III) Complexes from Spacer-Controlled Enantioselective Self-Assembly

Abstract

Two three-dimensional frameworks composed of doubly interpenetrating networks of the same topology but different stereoisomeric structures have been constructed from self-assembly of the chiral building block, Δ- or Δ-[Nd(ntb)₂]³⁺, with different spacers bipy and bpen (ntb = tris(2-benzimidazolylmethyl) amine, bipy = 4,4″-bipyridyl, bpen = trans-1,2-bis (4-pyridyl)ethylene). In the crystal structure of [Nd(ntb)₂](ClO₄)₃·3bipy·2H₂O the spacer bipy connects [Nd(ntb)₂]³⁺ cations of the same handedness to generate a chiral network Δ₃-Δ…(or Δ₃-Δ…){[Nd(ntb)₂](bipy)₃}³⁺∞, which is interpenetrated further by another identical network. The crystal structure of [Nd(ntb)₂](ClO₄)₃·3bpen·H₂O shows a topologically similar but achiral framework in which non-planar and planar bpen spacers connect cations of the same chirality and a pair of enantiomers, respectively, thus generating a three-dimensional racemate Δ₂Δ…(or Δ₂Δ-Δ…){[Nd(ntb)₂](bpen)₃}³⁺∞. Aggregation of the molecular species is effected by N-H…N hydrogen bonds, and the observed enantioselective self-assembly can be rationalized by π…π interactions between aromatic rings.     

Influence of Spacer Length on the Cellular Uptake of Polymeric Nanoparticles

Nanotechnology is finding ever increasing application in the life science arena where nanoparticles can be used to deliver cargoes in cells. However, a clear understanding of the relationship between the chemical properties of the particle and its uptake efficiency is lacking. Herein, the effects on particle cellular uptake following modification with a variety of spacers, all bearing a positive charge, but differing in length, and the influence on formation of the protein corona are investigated. Although no significant differences in the composition of the protein corona are detected, the spacer length influences the cellular uptake of the nanoparticles. These findings will allow the target‐orientated functionalisation of particles to increase the specificity of cellular uptake.

     

Guanidinylated Amphiphilic Polycarbonates with Enhanced Antimicrobial Activity by Extending the Length of the Spacer Arm and Micelle Self‐Assembly

Nine guanidinylated amphiphilic polycarbonates are rationally designed and synthesized. Each polymer has the same biodegradable backbone but different side groups. The influence of the hydrophobic/hydrophilic effect on antimicrobial activities and cytotoxicity is systematically investigated. The results verify that tuning the length of the spacer arm between the cationic guanidine group and the polycarbonate backbone is an efficient design strategy to alter the hydrophobic/hydrophilic balance without changing the cationic charge density. A spacer arm of six methylene units (CH₂)₆ shows the best antimicrobial activity (minimum inhibitory concentration, MIC = 40 µg mL^?1 against Escherichia coli, MIC = 20 µg mL^?1 against Staphylococcus aureus, MIC = 40 µg mL^?1 against Candida albicans) with low hemolytic activity (HC₅₀ > 2560 µg mL^?1). Furthermore, the guanidinylated polycarbonates exhibit the ability to self‐assemble and present micelle‐like nanostructure due to their intrinsic amphiphilic macromolecular structure. Transmission electron microscopy and dynamic light scattering measurements confirm polymer micelle formation in aqueous solution with sizes ranging from 82 to 288 nm.     

New liquid crystals derived from thiophene connected to the 1,2,3-triazole heterocycle

In this work, six new compound derivatives from thiophene were synthesised. The three symmetrical compounds were synthesised containing two heterocyclic 1,2,3-triazole on each side of thiophene, 2,5-disubstituted and the three non-symmetrical compounds were synthesised containing alkyne groups as a spacer in replacing one of these heterocycles. The structural modifications were made by changing the number of alkoxy groups in order to understand the relation between structure and mesomorphic behaviour. Some of the compounds presented liquid crystalline properties, smectic and nematic mesophases. The non-symmetrical compounds allowed for a low emission in the blue region.     

Enhanced photoluminescence intensity of 1.3-μm multi-layer InAs/InGaAs dots-in-well structure using the high growth temperature spacer layer step

The effects of growth temperature of the GaAs spacer layers (SPLs) on the photoluminescence (PL) efficiency of multi-layer GaAs-based 1.3-μm InAs/InGaAs dots-in-well (DWELL) structures have been investigated. It is found that the PL intensity of DWELLs is enhanced by incorporating a high growth temperature step for GaAs SPLs. This improved PL efficiency could be understood in term of reducing the non-radiative recombination centers. An extremely low continuous-wave room-temperature threshold current density of 35 A/cm² is achieved for an as-cleaved 5-layer device with emission at 1.31 μm by using this growth technique.     

Synthesis,characterization and properties of novel polyamides containing ferrocene unit and flexible spacers

Synthesis and characterization of ferrocene‐containing main‐chain polyamides are reported in this article. A new, interesting type of organometallic monomer (FDADO) based on ferrocene was prepared by interfacial condensation of 1,1′‐dichlorocarbonyl ferrocene with 2 mol 1,8‐diamino‐3,6‐dioxaoctane (DADO). A series of ferrocene‐based polyamides was prepared via polycondensation of the ferrocenyl diamine (FDADO) with different diacid chlorides using two different methods. The monomer and polymers were characterized by elemental analysis, infrared and NMR spectroscopy. The thermal stability and behavior of the synthesized polymers were evaluated by thermal gravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). The crystallinity of polymers was examined by X‐ray diffraction analysis. Inherent viscosity, solubility and flame‐retardancy of the polymers were also studied. The obtained polymers showed good heat‐resistance and flame‐retardancy, and improved solubility vs generally reported polyamides in some common organic solvents. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of novel derivatives of closo‐dodecaborate anion with azido group at the terminal position of the spacer

Two novel azido‐derivatives of closo‐dodecaborate anion with hydrophobic and hydrophilic spacers were prepared by reaction of tetrabutylammonium azide with cyclic oxonium derivatives of the closo‐dodecaborate anion. The compounds prepared can be regarded as precursors of derivatives of closo‐dodecaborate anion with amino group at the terminal position of a spacer or as building blocks for ‘click chemistry’, which are useful for preparation of various conjugates with targeting molecules. A concentration dependence of the ¹¹B NMR spectra of functionalized derivatives of closo‐dodecaborate anion was discovered, which is of great importance for analytical purposes. Copyright © 2006 John Wiley & Sons, Ltd.     

基于 ITS 序列探讨睡莲属植物的系统发育

对睡莲属Nymphaea L．11个种和外类群中国莲Nelumbo nucifera Gaertn．nrDNA的ITS区(包括ITS-1，5．8SrDNA和ITS-2)进行了序列测定．睡莲属植物的ITS序列总长度为678～711bp，ITS-1和ITS-2序列长度范围为246～275bp和266～275bp．当空位(gap)作缺失处理时，睡莲属植物ITS区全序列排序后的长度为735位点，其中有265个(101个位点在ITS-1区，164个位点在ITS-2区)为系统发育的信息位点．以Nelumbo nucifera Gaertn．为外类群，利用PAUP4．0b4a软件。采用最大简约法分析获得了2个最简约树，其步长为658，一致性指数(CI)和维持性指数(RI)值分别为0．8450和0．8555．利用2个最简约树获取严格一致树，结果表明：热带睡莲植物和耐寒睡莲植物分别聚成一支构成姊妹群，这与基于起源和对生态条件的不同要求、或根据心皮的排列方式而对睡莲属植物进行的传统分类一致．在热带睡莲植物内形成两个亚支，其内部支持率均为100％；耐寒睡莲植物内也形成了两个亚支，内部支持率分别为98％和85％．     

Imide-bridged diferrocene for protonation-controlled regulation of electronic communication

The imide-bridged diferrocene was synthesized and characterized, permitting the protonation-controlled regulation for the electronic communication between the two ferrocenyl moieties.     

My life with polymer science

This article describes the scientific investigations and accomplishments in the life of the author. After a dissertation on steroids, several years were spent on alkaloids and research on heterocyclic compounds. Much of the author's career was devoted to research on aldehyde polymerization, the discovery of the polymerization of higher aldehydes and their isotactic polymers, and haloaldehyde polymerization. The latter led to our work on the ceiling temperature of polymerization, on new polymerization techniques [involving the ceiling temperature and the concept of macromolecular asymmetry (polymer helicity)], and the genesis of chloral polymerization. Another important period was devoted to functional polymers, polymeric stabilizers, and polymeric drugs. Other research activities included studies of unusual polymers, head-to-head polymers, spacer groups in polymers, and oriental lacquers. Attention was also paid to the use of novel and unusual polymer intermediates, polymerization under extreme conditions and the preparation and behavior of uncommon polymer structures. Finally, it was recognized that macromolecules can be categorized with increasing frequency as polymers with broad and narrow molecular weight distributions and uniform polymers. The ultimate unity is isotopically pure uniform polymers, single macromolecular species. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 795–818, 2004