Electrically insulated molecular wires

This paper is an up-to-date mini-review based on literature data and own results regarding synthesis and properties of conducting (pseudo)rotaxane supramolecular structures. Conjugated polymers, such as polyarylene, polyheteroarylene, polyaniline, polyarylenevinylene or polyaryleneimine, were used as axle, while the macrocyclic components were cyclodextrins, cucurbiturils, cyclophanes or crown ethers. Properties of the supramolecular structure such as solubility, thermal or chemical stability, conductivity, etc. can be drastically modified by the inclusion of hydrophobic conjugated polymers inside the macrocycle, without any chemical modification. For instance, the photophysical properties (i.e. quantum yield of fluorescence and electroluminescence) of the supramolecular structures were enhanced when compared with uninsulated conjugated polymers. The doping process is also affected, because the access of a dopant to the conjugated chain is limited only to the uncovered domains of the conjugated chain.     

Stimulated by cyclodextrins high yield synthesis of azocrown analogues comprising pyrrole or imidazole residues

The influence of cyclodextrins (CDs) on the formation of azocrown ethers comprising pyrrole, imidazole and substituted imidazole has been studied. Pyrrole, imidazole, 2-methyl-, 4-methyl- and 4-phenylimidazole were coupled with bis-diazonium salts derived from bis-1,5-(2-aminophenoxy)-3-oxapentane or bis-1,8-(2-aminophenoxy)-3,6-dioxaoctane to form macrocyclic compounds with two azo units. The syntheses were performed under standard conditions in the presence of α-, β- or γ-CDs and the yield of the reaction products was compared with the results of plain experiments, i.e. without CDs. The results are discussed in terms of co-conformation of azole molecules embedded in CD cavity.

Pyrrole or imidazole or imidazole derivatives were coupled with bis-diazonium salts to form macrocycles with two azo units. The syntheses were performed under standard conditions in the presence of α-, β-, or γ-cyclodextrin and the yield of the reaction products was compared with the results of plain experiments, i.e. without CDs. The results are discussed in terms of co-conformation of azole molecules embedded in cyclodextrin cavity.     

Polymeric Nanocomposites—Polyhedral Oligomeric Silsesquioxanes (POSS) as Hybrid Nanofiller

Abstract

Polyhedral oligomeric silsesquioxane (POSS), a hybrid nanostructured macromer has been used in the last decade for preparation of polymeric nanocomposites. Its versatile chemistry, which lends it for almost infinite chemical modification, sets it apart from other nanostructured fillers like nanoclays, carbon nanotubes, and carbon nanofibers. Depending on its functionality, 3‐D network, bead or pendant type‐POSS based polymeric nanocomposites can be synthesized. These have the potential to be designed for products with specific nanostructures for specific end‐use applications. This article discusses the trends in current research involving use of POSS macromers for modification of mainly thermal and viscoelastic properties of various polymers.     

Polyhedral oligomeric silsesquioxanes as functional monomer to prepare hybrid monolithic columns for capillary electrochromatography and capillary liquid chromatography

A simple approach to fabricate hybrid monolithic column within the confines of fused-silica capillaries (75 μm i.d.) was introduced. A polyhedral oligomeric silsesquioxanes (POSS) reagent containing a methacrylate group was selected as functional monomer, and copolymerized with bisphenol A dimethacrylate (BPADMA) or ethylene dimethacrylate (EDMA) in the presence of porogenic solvents via thermally initiated free radical polymerization. After optimization of the preparation conditions, two POSS-containing hybrid monoliths were successfully prepared and exhibited good permeability and stability. By comparison of the separation efficiencies of the resulting poly(POSS-co-BPADMA) and poly(POSS-co-EDMA) monoliths in capillary electrochromatography (CEC) and capillary liquid chromatography (cLC), it was indicated the former has better column efficiencies for alkylbenzenes, phenols, anilines and PAHs in CEC and cLC than the latter. Particularly, the hybrid poly(POSS-co-BPADMA) monolith is more suitable for separation of PAHs due to π–π interaction between the analytes and aromatic rings in the surface of monolithic stationary phase.     

Syntheses and Crystal Structures of Two New Macrocyclic Compounds

Two new macrocyclic compounds, [Cu2(L)2](ClO4)4·2CH3OH (1) and [Cu(L)](ClO4)2·2H2O (2) (L = 1,3,10,12,15,18-hexaazatetracyclodocosane) were synthesized by condensation reactions involving amines and formaldehyde in the presence of copper anion. Compound 1 crystallizes in triclinic, space group Pí with a = 10.442(2), b = 14.197(3), c = 17.388(4), α = 91.218(4), β = 90.69(3), γ = 93.756(4)o, V = 2520.4(9)3, Z = 2, F(000) = 1260, Dc = 1.589 Mg/m3, Mr = 1205.92, μ = 1.137 mm-1, λ = 0.71073, the final R = 0.0668 and wR = 0.1573 for 9703 observed reflections with I > 2σ(I). Compound 2 crystallizes in monoclinic, space group C2/c with a = 16.911(2), b = 11.4172(15), c = 27.059(4), β = 107.787(2)o, V = 4974.7(12)3, Z = 8, F(000) = 2504, Dc = 1.610 Mg/m3, Mr = 602.92, μ = 1.155 mm-1, λ = 0.71073 , the final R = 0.0419 and wR = 0.1131 for 4374 observed reflections with I > 2σ(I).     

Controlled Click‐Assembly of Well‐Defined Hetero‐Bifunctional Cubic Silsesquioxanes and Their Application in Targeted Bioimaging

A general procedure for the assembly of hetero‐bifunctional cubic silsesquioxanes with diverse functionality and a perfectly controlled distribution of functional groups on the inorganic framework has been developed. The method is based on a two‐step sequence of mono‐ and hepta‐functionalization through the ligand‐accelerated copper(I)‐catalyzed azide–alkyne cycloaddition of a readily available octaazido cubic silsesquioxane. The stoichiometry of the reactants and the law of binomial distribution essentially determine the selectivity of the key monofunctionalization reaction when a copper catalyst with strong donor ligands is used. The methodology has been applied to the preparation of a set of bifunctional nano‐building‐blocks with orthogonal reactivity for the controlled assembly of precisely defined hybrid nanomaterials and a fluorescent multivalent probe for application in targeted cell‐imaging. The inorganic cage provides an improved photostability to the covalently attached dye as well as a convenient framework for the 3D multivalent display of the pendant epitopes. Thus, fluorescent bioprobes based on well‐defined cubic silsesquioxanes offer interesting advantages over more conventional fully organic analogues and ill‐defined hybrid nanoparticles and promise to become powerful tools for the study of cell biology and for biomedical applications.     

两个带呋喃悬臂不对称大环双核铜配合物的合成、结构及性质

合成并表征了2个不对称大环双核铜配合物[Cu₂（L¹）Cl₂]·CH₃CN（1）和[Cu₂（L²）Br₂]·CH₃CN·H₂O（2）。配合物与CT-DNA的作用通过紫外-可见光谱,粘度实验,圆二色谱和凝胶电泳实验进行了研究。紫外-可见光谱的结果表明配合物与DNA的结合常数分别为6.2×10⁵和7.2×10⁵,圆二色谱的实验表明配合物能与DNA较好的结合,粘度实验表明配合物与DNA的结合为非典型的插入模式,凝胶电泳实验显示配合物通过氧化机理对DNA有较强的切割活性。     

A Macrocyclic Furan with Accessible Oxidation States: Switching Between Aromatic and Antiaromatic Global Ring Currents

Macrocyclic furans are predicted to switch between global aromaticity and antiaromaticity, depending on their oxidation states. However, the macrocyclic furans reported to date are stabilized by electron withdrawing groups, which result in inaccessible oxidation states. To circumvent this problem, a post-macrocyclization approach was applied to introduce methylene-substituted macrocyclic furans, which display an extremely low oxidation potential of −0.23 vs. Fc/Fc⁺, and are partially oxidized in ambient conditions. Additional oxidation to the dication results in aromaticity switching to a global 30πe⁻ aromatic state, as indicated by the formation of a strong diatropic current observed in the ¹H NMR spectrum. NICS and ACID calculations support this trend and provide evidence for a different pathway for the global current in the neutral and dicationic states. According to these findings, macrocyclic furans can be rendered as promising p-type materials with stable oxidation states.     

Enantioselective Liquid Chromatographic Separations Using Macrocyclic Glycopeptide-Based Chiral Selectors

Numerous chemical compounds of high practical importance, such as drugs, fertilizers, and food additives are being commercialized as racemic mixtures, although in most cases only one of the isomers possesses the desirable properties. As our understanding of the biological actions of chiral compounds has improved, the investigation of the pharmacological and toxicological properties has become more and more important. Chirality has become a major issue in the pharmaceutical industry; therefore, there is a continuous demand to extend the available analytical methods for enantiomeric separations and enhance their efficiency. Direct liquid chromatography methods based on the application of chiral stationary phases have become a very sophisticated field of enantiomeric separations by now. Hundreds of chiral stationary phases have been commercialized so far. Among these, macrocyclic glycopeptide-based chiral selectors have proved to be an exceptionally useful class of chiral selectors for the separation of enantiomers of biological and pharmacological importance. This review focuses on direct liquid chromatography-based enantiomer separations, applying macrocyclic glycopeptide-based chiral selectors. Special attention is paid to the characterization of the physico-chemical properties of these macrocyclic glycopeptide antibiotics providing detailed information on their applications published recently.