Thermomechanical behaviors and dielectric properties of polyaniline‐doped para‐toluene sulfonic acid/epoxy resin composites

Composites based on conductive organic/inorganic fillers dispersed in insulating matrix have been widely investigated because of their widespread applications such as electromagnetic shielding, electrostatic discharge, and sensors. In this context, novel composite materials based on epoxy resin matrix charged with polyaniline (PANI)‐doped para‐toluene sulfonic acid were elaborated. Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy were used to check the structure and the morphology of the samples. Viscoelastic behavior and thermal stability of the composites were explored by dynamic mechanical thermal analysis and thermogravimetric analysis. It was shown that the PANI particles exhibited a partial crystalline structure and were homogeneously dispersed in epoxy matrix. Consequently, this structure affected the thermal stability and viscoelastic properties of the composites. Furthermore, the dielectric and electrical properties were investigated up to 1 MHz. Measurements of dielectric properties revealed that with loading fillers in matrix, the dielectric parameters increased to high values at low frequency then decreased at values around 40 and 32 of real and imaginary parts, respectively, at 1 MHz with 15% of PANI content. Copyright © 2011 John Wiley & Sons, Ltd.     

A supramolecular cup-and-ball C60-porphyrin conjugate system

In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit.     

Novel heteroleptic cis-(C--N)2Pd(II) chelates for the preparation of enantiopure planar chiral cyclopalladated 2-[tricarbonyl(eta6-phenyl)chromium]pyridine

In the presence of large amounts of [Me4N]Cl, the reaction of ortho-chloromercurated 2-[(eta6-phenyl)tricarbonylchromium]pyridine with mu-chloro cyclopalladated aromatic compounds yields a series of new heteroleptic heterodinuclear cis-(C--N)2Pd(II) complexes, which are valuable precursors of planar chiral cyclopalladated (eta6-arene)Cr(CO)3 complexes.     

Molecular tectonics: infinite cationic double stranded helical coordination networks

Upon crystallisation of two bismonodentate tectons based on two pyridine units, interconnected at the meta position by a tetra- or hexa-ethylene glycol fragment and Ag+ cation, double stranded helical infinite coordination networks were formed and structurally characterised. The cationic double helical architectures obtained may be regarded as analogues of DNA in terms of topology.     

Helicity‐Encoded Molecular Strands: Efficient Access by the Hydrazone Route and Structural Features

Control over the folding of molecular strands may be achieved by appropriate choice of the constituting subunits, in particular for chains of specific heterocycles such as sequences of directly connected pyridine (py) and pyrimidine (pym) rings, which are known to fold into extended helical structures. Since the hydrazone (hyz) group represents an isomorphic analogue of a py site, the condensation of hydrazine and carboxaldehyde derivatives of pym offers a very efficient approach to strands incorporating hyz instead of py units and constituted by sequences of alternating hyz and pym groups. A series of such strands of different lengths, up to ten hyz units, i.e., 1 – 7 , were synthesized. Their spectral properties indicate that they fold indeed into helical shapes. Extensive characterization was performed in solution by ¹HNMR spectroscopy and in the solid state by determination of the crystal structures of eight such strands. They all display the expected helical geometry with up to 3 ¹/₃ turns and direct stacking contacts. The efficiency and flexibility of the synthetic approach as well as its wide potential for generation of diversity through lateral decoration make the (hyz? pym) subunit a particularly attractive helicity codon.     

Synthesis and Characterization of Various Benzyl Diethylenetriaminepentaacetic Acids (dtpa) and Their Paramagnetic Complexes,Potential Contrast Agents for Magnetic Resonance Imaging

Four derivatives of diethylenetriaminepentaacetic acid (=3,6,9‐tris(carboxymethyl)‐3,6,9‐triazaundecanedioic acid (H₅dtpa)), potential contrast agents for magnetic resonance imaging (MRI), carrying benzyl groups at various positions of the parent structure were synthesized and characterized by a thorough multinuclear NMR study, i.e., the (S)‐ and (R)‐stereoisomers 1a and 1b of 4‐benzyl‐3,6,9‐tris(carboxymethyl)‐3,6,9‐triazaundecanedioic acid (H₅[(S)‐(4‐Bz)dtpa] and H₅[(R)‐(4‐Bz)dtpa], the diamide derivative N,N″‐bis[(benzylcarbamoyl)methyl]diethylenetriamine‐N,N′,N″‐triacetic acid (=3,9‐bis[2‐(benzylamino)‐2‐oxoethyl]‐6‐(carboxymethyl)‐3,6,9‐triazaundecanedioic acid; H₃[dtpa(BzA)₂]; 2 ), and the diester derivative N,N″‐bis{[(benzyloxy)carbonyl]methyl}diethylenetriamine‐N,N′,N″‐triacetic acid (=3,9‐bis[2‐(benzyloxy)‐2‐oxoethyl]‐6‐(carboxymethyl)‐3,6,9‐triazaundecanedioic acid; H₃[dtpa(BzE)₂]; 3 ). From the ¹⁷O‐NMR chemical shift of H₂O induced by their dysprosium complexes with ligands 1 – 3 , it was concluded that only one H₂O molecule is contained in the first coordination sphere of these lanthanide complexes. The rotational correlation times (τ_R) of the complexes were estimated from the ²H‐NMR longitudinal relaxation rate of the deuterated diamagnetic lanthanum complexes. The exchange time of the coordinated H₂O molecule (τ_M) was studied through the temperature dependence of the ¹⁷O‐NMR transverse relaxation rate. As compared to [Gd(dtpa)]²⁻, the H₂O‐exchange rate is faster for [Gd{(S)‐(4‐Bz)dtpa}]²⁻ and [Gd{(R)‐(4‐Bz)dtpa}]²⁻‐, slower for [Gd{dtpa(BzA)₂}], and almost identical for [Gd{dtpa(BzE)₂}]. The analysis of the ¹H‐relaxivity of the gadolinium complexes recorded from 0.02 to 300 MHz established that i) the relaxivity of [Gd{dtpa(BzE)₂}] is similar to that of [Gd(dtpa)]²⁻, ii) the slightly slower molecular rotation of [Gd{dtpa(BzA)₂}] induces a mild enhancement of its relaxivity, and iii) the marked increase of relaxivity of [Gd{(S)‐(4‐Bz)dtpa}]²⁻ and [Gd{(R)‐(4‐Bz)dtpa}]²⁻ mainly results from an apparently shorter distance between the gadolinium ion and the H₂O protons of the coordinated H₂O molecule.     

Water‐Soluble Flavonol (=3‐Hydroxy‐2‐phenyl‐4H‐1‐benzopyran‐4‐one) Derivatives: Chemical Synthesis,Colouring, and Antioxidant Properties

Water‐soluble derivatives of rutin, a very common glycoside of quercetin (=3,3′,4′,5,7‐pentahydroxyflavone=2‐(3,4‐dihydroxyphenyl)‐3,5,7‐trihydroxy‐4H‐1‐benzopyran‐4‐one) and a potent plant antioxidant from the flavonol family, were synthesized by simple chemical procedures aimed at introducing carboxy or sulfo groups at the sugar moiety (Scheme 1). Such derivatives form stable molecular complexes with malvin, a polyphenolic pigment from the anthocyanin family, and thereby prove to be very effective in the enhancement (hyperchromism) and variation (bathochromism) of natural colours. The H₂O‐solubilizing carboxylate and sulfate groups are shown to deeply modify the enthalpy‐entropy balance of the pigment‐flavonol complexation (copigmentation). A molecular interpretation of the complexation‐induced bathochromic shift in the pigment VIS band is proposed. Finally, the H₂O‐soluble rutin derivatives are shown to retain the high antioxidant ability of rutin as evidenced by their efficient trapping of the coloured radical DPPH (=2,2‐diphenyl‐1‐(2,4,6‐trinitrophenyl)hydrazyl).     

Efficient access to fluorinated homoallylic alcohols through an indium promoted fluoroallylation reaction

Herein, an efficient access to fluorinated homoallylic alcohol is reported. The fluorinated alcohols were obtained in good to excellent yield using indium and halo-fluorinated allylic derivatives. The developed methodology using γ-substituted halo-fluorinated allylic derivatives gave the corresponding α-substituted fluorinated homoallylic alcohol in good yields and good diastereoselectivities up to 86:14.     

Kinetics and efficiency displayed by supported and suspended TiO2 catalysts applied to the disinfection of Escherichia coli

TiO₂-mediated photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including photoelectrochemical conversion, self-cleaning surfaces, and especially water purification systems. The dimensionality of the structure of a TiO₂ material can affect its properties, functions, and more specifically, its photocatalytic performance. In this work, the photocatalytic inactivation of Gram-negative Escherichia coli using three photocatalysts, differing in their structure and other characteristics, was studied in a batch reactor under UVA light. The aim was to establish the disinfection efficiency of solid TiO₂ compared with that of suspended catalysts, widely considered as reference cases for photocatalytic water disinfection. The bacterial inactivation profiles obtained showed that: (1) the photoinactivation was exclusively related to the quantity of photons retained per unit of treated volume, irrespective of the characteristics of the photocatalyst and the emitted light flux densities; (2) across the whole UV light range studied, each of the photocatalytic solids was able to achieve more than 2 log bacterial inactivation with less than 2 h UV irradiation; (3) none of the used catalysts achieved a total bacterial disinfection during the treatment time. For each of the catalysts the quantum yield has been assessed in terms of disinfection efficiency, the 2D material showed almost the same performance as those of suspended catalysts. This catalyst is promising for supported photocatalysis applications.     

1,10‐Phenanthroline and Non‐Symmetrical 1,3,5‐Triazine Dipicolinamide‐Based Ligands For Group Actinide Extraction

The synthesis and evaluation of new extractants for spent nuclear fuel reprocessing are described. New bitopic ligands constituted of phenanthroline and 1,3,5‐triazine cores functionalized by picolinamide groups were designed. Synthetic routes were investigated and optimized to obtain twelve new polyaza‐heterocyclic ligands. In particular, an efficient and versatile methodology was developed to access non‐symmetric 2‐substituted‐4,6‐di(6‐picolin‐2‐yl)‐1,3,5‐triazines from the 1,3,5‐triazapentadiene precursor in the presence of anhydride reagents. Extraction studies showed the ability of both ligand series to extract and separate actinides selectively at different oxidation states (U^VI, Np^V,VI, Am^III, Cm^III, and Pu^IV) from an acidic solution (3 M HNO₃). Phenanthroline‐based ligands show the most promising efficiency for use in the group actinide extraction (GANEX) process due to a higher number of donor nitrogen atoms and a suitable pre‐organization of the dipicolinamide‐1,10‐phenanthroline architecture.