A Study of Polymerization‐Induced Phase Separation as a Route to Produce Porous Polymer–Metal Materials

We report the results of the experimental study of the preparation of hybrid porous polymer material carrying gold nanorods (NRs) on the surface of pores. The material was prepared by utilizing two effects occurring concurrently: the photoinitiated polymerization‐induced phase separation in the polymer–solvent mixture and the migration of the NRs to the interface between the polymer and the porogen solvent. We show that the enrichment of the interface with the NRs is enhanced at high polymerization rate leading to the rapid phase separation. By contrast, more rapid increase in viscosity achieved at high polymerization rate does not have a significant effect on the segregation of NRs to the surface of pores.

     

A Versatile Approach for Synthesis of 2,3-Dimethyl Chroman-4-ones,Intermediate for Calanolide Anti-HIV Agents,VIA Aldol/Mitsunobu Reactions

Combined aldol/Mitsunobu reactions have been employed for the first time for synthesis of 2,3-dimethyl chroman-4-ones, intermediates for calanolide anti-HIV agents. Thus, the lithium enolate of chromene 1 reacted with acetaldehyde at -78°C to afford the aldol products 4 and 5. Under Mitsunobu conditions (Ph₃P/DEAD), the syn aldol product 4 led to the formation of trans-2,3-dimethyl chroman-4-one 2 while the anti aldol product 5 yielded both trans and cis derivatives (2 and 3). The use of other phosphorous and azo compounds in this reaction has also been investigated.     

Maleic Anhydride Crosslinked Alginate-Chitosan Blend Membranes for Pervaporation of Ethylene Glycol-Water Mixtures

Calcium alginate-chitosan (CA/CS) blended membranes were prepared and crosslinked with maleic anhydride (MA) for the pervaporation (PV) separation of ethylene glycol (EG)/water mixtures at 30°C. The structure and properties of blend membranes were studied with the aid of FTIR, XRD, TGA, and SEM. The effect of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance of the MA crosslinked membranes were determined in terms of flux, selectivity, and pervaporation separation index. Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the blend membranes in pure, as well as in binary mixtures. The experimental results suggested that the crosslinked membrane (M-CA/CS) exhibited a good selectivity of 302 at a normalized flux of 0.38 kg.m^{? 2}.h^{? 1}.10 μ m at 30°C for 96.88 wt% EG aqueous solution.     

Triphenylphosphine-Based Covalent Organic Frameworks and Heterogeneous Rh-P-COFs Catalysts

The synthesis of phosphine-based functional covalent organic frameworks (COFs) has attracted great attention recently. Herein, we present two examples of triphenylphosphine-based COFs (termed P-COFs) with well-defined crystalline structures, high specific surface areas, and good thermal stability. Furthermore, rhodium catalysts with these P-COFs as support material show high turnover frequency for the hydroformylation of olefins, as well as excellent recycling performance. This work not only extends the phosphine-based COF family, but also demonstrates their application in immobilizing homogeneous metal-based (e.g., Rh-phosphine) catalysts for application in heterogeneous catalysis.     

Tetrahydroquinoline and tetrahydroisoquinoline mixed ligand rhenium complexes with the SNS/S donor atom set

New oxorhenium complexes with 3‐methylazapentane‐1,5‐dithiolate (SNMeS) and thiol functionalized monodentate tetrahydroquinolyl and tetrahydroisoquinolyl derivatives have been synthesized by simultaneous reaction of [PPh₃]₂[Re(O)Cl₃] with tridentate HSNMeSH and the corresponding N‐heterocycle containing thiol. The characterization of complexes involved elemental analysis, IR, ¹H and ¹³C NMR spectroscopy and X‐ray crystallographic analysis. The nature of the heterocycle in monodentate ligand, even situated at the distance of two methylene group length, has been found to have a significant influence on the molecular conformation. Metal complexes were found to be active in psychotropic in vivo and cytotoxicity in vitro screening. Copyright © 2007 John Wiley & Sons, Ltd.     

Chemistry and thermal decomposition of trinitropyrazoles

New energetic compounds-3,4,5-1H-trinitropyrazole (TNP), 1-methyl-3,4,5-1H-trinitropyrazole (MTNP) and ammonium 3,4,5-1H-TNP have been synthesized and characterized by thermal analysis. These new compounds can be considered as promising since the high heat of formation for them. To estimate the process of their thermal decomposition, the original technique for computer simulation was used. We generated the models for the mechanisms of thermal decay of synthesized compounds which allowed obtaining comprehensive spectrum of transformations of intermediates on the way to the final products of thermolysis. The preferred pathways were determined based on the results of activation energy (E _a) calculations (DFT 6-311⁺⁺G** method) of thermal decay reactions for each generated pathways. The thermal decomposition has been studied also experimentally by thermogravimetry (TG) and differential scanning calorimetry. Kinetic parameters of thermolysis were evaluated by model-free and -fitting methods using TG data. Model-free method has given not reliable data for TNP and MTNP compounds, whereas model-fitting yields kinetic equations with the good correlation with experimental TG data.     

Synthesis and reactivity of acyclic and macrocyclic uracils bridged with five-membered heterocycles

Replacement of terminal atoms of Br in 1,3-bis(bromopentyl)-5(6)-substituted uracils with 2-mercapto-5-methyl-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercaptoimidazole, and 2-mercaptobenzimidazoles resulted in a series of acyclic compounds and isomeric heterocyclophanes. Structures of macrocyclic regioisomers were unambiguously determined by NMR data. One of the regioisomers exhibits a hypochromic effect with respect to model compounds. The acyclic uracils obtained bridged with five-membered heterocycles are alkylated with methyliodide and methyl tosylate, and oxidated with m-CPBA, H₂O₂, and I₂.     

Optical sensing quantum dot-labeled polyacrolein particles prepared by layer-by-layer deposition technique

Optical sensing polymer particles with tailored semiconductor nanocrystal (QD) loading are prepared by layer-by-layer deposition technique (LbL). Polyacrolein particles of 1.2 μm diameter are used as solid support for deposition of hydrophilic CdSe/ZnS nanocrystal/polyelectrolyte multilayers formed by electrostatic interactions. The pH-dependent fluorescence of QDs and pH-dependent conformations of polyelectrolytes, which likely passivate the surface state of nanocrystals, allow a creation of both mono- and multiplex coded polymer particles with pH-dependent fluorescence intensity. Bovine serum albumin (BSA) as outermost layer makes it possible to design the optical sensing polymer particles with reversibly responded fluorescence at pH variations. The fluorescence of such polymer particles with BSA outer layer is sensitive to copper(II) ion while the fluorescence of these particles is practically insensitive to the other divalent cations (Zn(2+), Ca(2+), Ba(2+), Co(2+), Mg(2+)). The detection limit of Cu(2+) is about 15 nM. Adaptation of LbL method to prepare QD-labeled polymer particles with enhanced complexity (e.g. several types of QDs, multiple biofunctionality) is expected to open new opportunities in biotechnological applications.