Electrogenerated Fe(I) Porphyrins: Efficient Electrocatalysts for Reductive Dechlorination of DDT in N,N′‐Dimethylformamide

Two iron(I) porphyrins were electrogenerated and then utilized as catalysts for the reductive dechlorination of 1,1‐bis(4‐chlorophenyl)‐2,2,2‐trichloroethane (DDT) in N,N′‐dimethylformamide. No reaction is observed between DDT and the Fe(III) or Fe(II) forms of the porphyrin, but the electrogenerated Fe(I) porphyrin efficiently catalyzes the electroreduction of DDT to give (1,1‐bis(4‐chlorophenyl)‐2,2‐dichloroethane) DDD, (1,1‐bis(4‐chlorophenyl)‐2,2‐dichloroethylene) DDE and (1,1‐bis(4‐chlorophenyl)‐2‐dichloroethane) DDMU as determined by GC‐MS analysis. The reductive dechlorination was monitored by electrochemistry, controlled potential electrolysis and spectroelectrochemistry and a mechanism for the reaction involving the reduced porphyrins and DDT is proposed. Comparisons are also made between the catalytic properties of metalloporphyrins containing iron, cobalt and manganese central metal ions under the same solution conditions.     

Preparation of a butyl–silica hybrid monolithic column with a “one-pot” process for bioseparation by capillary liquid chromatography

A butyl–silica hybrid monolithic column for bioseparation by capillary liquid chromatography (cLC) was prepared with butyl methacrylate and alkoxysilanes through a “one-pot” process. The effects of polycondensation temperature, volume percentage of N,N′-dimethylformamide, and content of cetyltrimethylammonium bromide and butyl methacrylate on the morphologies of the hybrid monolithic columns prepared were investigated in detail. Baseline separations of proteins and small peptides on the hybrid monolithic column were achieved by cLC with gradient elution. In addition, the resulting hybrid column was also applied for analysis of tryptic digests of bovine serum albumin by cLC coupled with tandem mass spectrometry. The results demonstrate its potential application in separation of complex biological samples.     

Natural products and their derivatives as G-quadruplex binding ligands

G-quadruplexes comprise a class of secondary structures that are formed in guanine-rich sequences in eukaryotic genomes and play a crucial role in the regulation of many biological events. G-quadruplexes have become targets for anticancer drugs with high selectivity vs. duplex DNA and low cytotoxicity against normal cells. Natural products and their derivatives display polymorphism, structural complexity, and potent activity. It is, therefore, reasonable to seek ligands targeting G-quadruplexes from natural products. Recently, many successful examples have been reported, showing ligands with excellent anticancer activities. In this review, we summarized the development of research on natural products and derivatives that target G-quadruplex structures in an effort to guide future studies.     

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.     

Facile and Rapid Synthesis of 9H-Carbazole-9-Carboxylic Acids Under Microwave Irradiation

The reaction of halogenated 9H-carbazoles or carbazole with bromoesters in DMF under microwave irradiation readily affords a series of 9H-carbazoles-9-hydroxylic acids.     

Synthesis and Crystal Structure of Two Succinato‐Bridged Macrocyclic Nickel(II) Complexes

Two dinuclear succinato‐bridged nickel(II) complexes [Ni(RR‐L)]₂(μ‐SA)(ClO₄)₂ ( 1 ) and [Ni(SS‐L)]₂(μ‐SA)(ClO₄)₂ ( 2 ) (L = 5, 5, 7, 12, 12, 14‐hexamethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, SA = succinic acid) were synthesized and characterized by EA, Circular dichroism (CD), as well as IR and UV/Vis spectroscopy. Single crystal X‐ray diffraction analyses revealed that the Ni^II atoms display a distorted octahedral coordination arrangement, and the succinato ligand bridges two central Ni^II atoms in a bis bidentate fashion to form dimers in 1 and 2 . The monomers of {[Ni(RR‐L)]₂(μ‐SA)}²⁺ and {[Ni(SS‐L)]₂(μ‐SA)}²⁺ are connected by O–H ··· O and N–H ··· O hydrogen bonds into a 1D right‐handed and left‐handed helical chain along the b axis, respectively. The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy.     

Tribological behaviors of a novel trilayer nanofilm: the influence of outer chain length and interlayer thickness

Polydopamine (coded as PDA) is reported to be very adhesive and reactive due to the attached functional groups, such as amine and hydroxyl groups. In this work, taking advantage of the condensation between Si–OH of the hydroxylated alkyltrichlorosilane (ATS) and C–OH on PDA surface, ATS molecules with different chain carbon number of 10, 14 and 18 were grafted onto the 3‐aminopropyl triethoxysilane (APTES)‐PDA dual‐layer film, which was composed of PDA outerlayer and APTES underlayer, on Si substrate. Thus, hydrophobic trilayer films coded as APTES‐PDA‐ATS were prepared successfully. In order to reveal the dependence of the tribological behaviors upon the microstructures of the film, tribological experiments were conducted on an atomic force microscope and a ball‐on‐plate tribometer. Experimental results showed that the (micro‐) friction reducing (characterized by a parameter of relative friction coefficient or friction coefficient, RFC or FC) and macro‐wear resisting (characterized by anti‐wear life) behaviors were related with the chain length of outerlayer and the PDA thickness. Specifically, on one hand, as the chain length increases, RFC/FC decreased and macro anti‐wear life lengthened; on the other hand, as PDA gets thicker, RFC increased and the anti‐wear life enhanced. Copyright © 2013 John Wiley & Sons, Ltd.     

Expanded Organic Building Units for the Construction of Highly Porous Metal–Organic Frameworks

Two new organic building units that contain dicarboxylate sites for their self‐assembly with paddlewheel [Cu₂(CO₂)₄] units have been successfully developed to construct two isoreticular porous metal–organic frameworks (MOFs), ZJU‐35 and ZJU‐36, which have the same tbo topologies (Reticular Chemistry Structure Resource (RCSR) symbol) as HKUST‐1. Because the organic linkers in ZJU‐35 and ZJU‐36 are systematically enlarged, the pores in these two new porous MOFs vary from 10.8 Å in HKUST‐1 to 14.4 Å in ZJU‐35 and 16.5 Å in ZJU‐36, thus leading to their higher porosities with Brunauer–Emmett–Teller (BET) surface areas of 2899 and 4014 m² g^?1 for ZJU‐35 and ZJU‐36, respectively. High‐pressure gas‐sorption isotherms indicate that both ZJU‐35 and ZJU‐36 can take up large amounts of CH₄ and CO₂, and are among the few porous MOFs with the highest volumetric storage of CH₄ under 60 bar and CO₂ under 30 bar at room temperature. Their potential for high‐pressure swing adsorption (PSA) hydrogen purification was also preliminarily examined and compared with several reported MOFs, thus indicating the potential of ZJU‐35 and ZJU‐36 for this important application. Studies show that most of the highly porous MOFs that can volumetrically take up the greatest amount of CH₄ under 60 bar and CO₂ under 30 bar at room temperature are those self‐assembled from organic tetra‐ and hexacarboxylates that contain m‐benzenedicarboxylate units with the [Cu₂(CO₂)₄] units, because this series of MOFs can have balanced porosities, suitable pores, and framework densities to optimize their volumetric gas storage. The realization of the two new organic building units for their construction of highly porous MOFs through their self‐assembly with [Cu₂(CO₂)₄] units has provided great promise for the exploration of a large number of new tetra‐ and hexacarboxylate organic linkers based on these new organic building units in which different aromatic backbones can be readily incorporated into the frameworks to tune their porosities, pore structures, and framework densities, thus targeting some even better performing MOFs for very high gas storage and efficient gas separation under high pressure and at room temperature in the near future.     

Tetrasubstituted pyrazinones derived from the reaction of praziquantel with N-bromosuccinimide

When praziquantel was exposed to N-bromosuccinimide in the presence of ethanol, a tricyclic 3-bromo-1-ethoxy pyrazinone was formed. From this and the analogous 1,3-dibromopyrazinone, a small library of 3-alkylamino-1-ethoxy, 1,3-dialkoxy, 3-alkoxy-1-bromo, and 3-alkylamino-1-bromo substituted pyrazinones were synthesized in high yields.