A new catalytic method for the synthesis of selectively substituted biphenyls containing an oxoalkyl chain

A novel reaction sequence leading to the synthesis of substituted biphenyls containing a carbonyl group in an aliphatic chain has been achieved in one-pot reaction starting from iodoarenes and allylic alcohols under the catalytic action of palladium and norbornene. The latter is temporarily incorporated into a palladacycle, which directs the reaction towards the selective formation of an arylaryl bond. Norbornene spontaneously deinserts to allow the biphenylylpalladium bond thus formed to react in its turn with the allylic alcohol.     

Conformational flexibility of a synthetic glycosylaminoglycan bound to a fibroblast growth factor. FGF-1 recognizes both the (1)C(4) and (2)S(O) conformations of a bioactive heparin-like hexasaccharide

The first direct NMR determination of the conformation of a conformationally flexible heparin-like hexasaccharide bound to a key receptor, FGF-1, is described. The determination has been based on the use of a 13C-labeled protein and a regular 12C sugar. FGF-1 recognizes several conformations of the iduronic moieties of the hexasaccharide. Therefore, this case is different than that described for the controversial recognition of heparin-like saccharides by AT-III, which seems to recognize just one conformation of the iduronic acid residues.     

Thermal and viscoelastic properties of novel epoxy-dicyclopentadiene-terminated polyesters-styrene copolymers

This article presents the studies on the thermal and viscoelastic properties of novel epoxy-dicyclopentadiene-terminated polyesters-styrene copolymers. The novel materials were prepared during a three step process including the addition reaction of maleic acid to norbonenyl double bond of dicyclopentadiene; polycondensation of acidic ester of dicyclopentadiene, cyclohex-4-ene-dicarboxylic anhydride, maleic anhydride, and suitable glycol: ethylene, diethylene, or triethylene glycol; and the epoxidation process of prepared polyesters. It allowed obtaining novel epoxy-dicyclopentadiene-terminated polyesters which were successfully used as a component of different styrene content (10?C80?mass%) copolymers. The influence of the structures of polyester and styrene content on the cross-linking density (v _e), tg?? _max, tg?? _max height, storage modulus (E?? _20?°C), FWHM values as well as the thermal stability of copolymers was evaluated by TG, DSC, and DMA analyses and discussed.     

Tailoring the Structure of Two‐Dimensional Self‐Assembled Nanoarchitectures Based on NiII–Salen Building Blocks

The synthesis of a series of Ni^II–salen‐based complexes with the general formula of [Ni(H₂L)] (H₄L=R²‐N,N′‐bis[R¹‐5‐(4′‐benzoic acid)salicylidene]; H₄L1: R²=2,3‐diamino‐2,3‐dimethylbutane and R¹=H; H₄L2: R²=1,2‐diaminoethane and R¹=tert‐butyl and H₄L3: R²=1,2‐diaminobenzene and R¹=tert‐butyl) is presented. Their electronic structure and self‐assembly was studied. The organic ligands of the salen complexes are functionalized with peripheral carboxylic groups for driving molecular self‐assembly through hydrogen bonding. In addition, other substituents, that is, tert‐butyl and diamine bridges (2,3‐diamino‐2,3‐dimethylbutane, 1,2‐diaminobenzene or 1,2‐diaminoethane), were used to tune the two‐dimensional (2D) packing of these building blocks. Density functional theory (DFT) calculations reveal that the spatial distribution of the LUMOs is affected by these substituents, in contrast with the HOMOs, which remain unchanged. Scanning tunneling microscopy (STM) shows that the three complexes self‐assemble into three different 2D nanoarchitectures at the solid–liquid interface on graphite. Two structures are porous and one is close‐packed. These structures are stabilized by hydrogen bonds in one dimension, while the 2D interaction is governed by van der Waals forces and is tuned by the nature of the substituents, as confirmed by theoretical calculations. As expected, the total dipolar moment is minimized     

HOMO Stabilisation in π‐Extended Dibenzotetrathiafulvalene Derivatives for Their Application in Organic Field‐Effect Transistors

Three new organic semiconductors, in which either two methoxy units are directly linked to a dibenzotetrathiafulvalene (DB‐TTF) central core and a 2,1,3‐chalcogendiazole is fused on the one side, or four methoxy groups are linked to the DB‐TTF, have been synthesised as active materials for organic field‐effect transistors (OFETs). Their electrochemical behaviour, electronic absorption and fluorescence emission as well as photoinduced intramolecular charge transfer were studied. The electron‐withdrawing 2,1,3‐chalcogendiazole unit significantly affects the electronic properties of these semiconductors, lowering both the HOMO and LUMO energy levels and hence increasing the stability of the semiconducting material. The solution‐processed single‐crystal transistors exhibit high performance with a hole mobility up to 0.04 cm² V^?1 s^?1 as well as good ambient stability.     

Thermal properties,phase transitions,vibrational and reorientational dynamics of [Mn(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>

[Mn(NH₃)₆](NO₃)₂ crystallizes in the cubic, fluorite (C1) type crystal lattice structure (Fm \( \overline{3} \) m) with a = 11.0056 Å and Z = 4. Two phase transitions of the first-order type were detected. The first registered on DSC curves as a large anomaly at T _C1 ^h  = 207.8 K and T _C1 ^c  = 207.2 K, and the second registered as a smaller anomaly at T _C2 ^h  = 184.4 K and T _C2 ^c  = 160.8 K (where the upper indexes h and c denote heating and cooling of the sample, respectively). The temperature dependence of the full width at half maximum of the band associated with the δ_s(HNH)F_1u mode suggests that the NH₃ ligands in the high temperature and intermediate phase reorientate quickly with correlation times in the order of several picoseconds and with activation energy of 9.9 kJ mol^?1. In the phase transition at T _C2 ^c probably only a some of the NH₃ ligands stop their reorientation, while the remainders continue to reorientate quickly with activation energy of 7.7 kJ mol^?1. Thermal decomposition of the investigated compound starts at 305 K and continues up to 525 K in four main stages (I–IV). In stage I, ²/₆ of all NH₃ ligands were seceded. Stages II and III are connected with an abruption of the next ²/₆ and ¹/₆ of total NH₃, respectively, and [Mn(NH₃)](NO₃)₂ is formed. The last molecule of NH₃ per formula unit is freed at stage IV together with the simultaneous thermal decomposition of the resulting Mn(NO₃)₂ leading to the formation of gaseous products (O₂, H₂O, N₂ and nitrogen oxides) and solid MnO₂.     

Preparation of a new Cd(II)-imprinted polymer and its application to determination of cadmium(II) via flow-injection-flame atomic absorption spectrometry

A new cadmium(II)-imprinted polymer based on cadmium(II) 2,2′-{ethane-1,2-diylbis[nitrilo(E)methylylidene]} diphenolate-4-vinylpyridine complex was obtained via suspension polymerization. The beads were used as a minicolumn packing for flow-injection-flame atomic absorption spectrometry (FI-FAAS) determination of cadmium(II) in water samples. Sorption effectiveness was optimal within pH range of 6.6-7.7. Nitric acid, 0.5% (v/v) was used as eluent. Fast cadmium(II) sorption by the proposed material enabled to apply sample flow rates up to 10 mL min⁻¹ without loss in sorption effectiveness. Enrichment factor (EF), concentration efficiency (CE) and limit of detection (LOD, 3σ) found for 120-s sorption time were 117, 39.1 min⁻¹ and 0.11 μg L⁻¹, respectively. Sorbent stability was proved for at least 100 preconcentration cycles (RSD = 2.9%). When compared to non-imprinted polymer the new Cd(II)-imprinted polymer exhibited improved selectivity towards cadmium(II) against other heavy metal ions, especially Cu(II) and Pb(II), as well as light metal ions. Accuracy of the method was tested for ground water and waste water certified reference materials and fortified water. The method was applied to Cd(II) determination in natural water samples.     

Investigation of Lewis Acid versus Lewis Base Catalysis in Asymmetric Cyanohydrin Synthesis

The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}₂] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X=EtOSO₃ or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}₂O] and triphenylphosphine oxide, a non‐linear Hammett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron‐deficient. These results suggested that the aluminium complex/triphenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ketones and this was found to be the case.     

The mass spectrometric study on aminohydroxamic acids‐based metallacrowns

Electrospray ionization mass spectrometry (MS) has been widely used to detect noncovalent interactions in supramolecular compounds, especially in biological systems. In our work, we present the application of the electrospray ionization MS technique to characterize the metallamacrocycles, known as metallacrowns. This project involves investigations of the aminohydroxamic acids structure and chirality influence on formation of ternary 12‐metallacrown‐4 complexes. For our experiments, we used a series of β‐aminohydroxamic acids and derivatives of histidinehydroxamic acid. A high stability of the studied supramolecular systems in the gas phase was confirmed by MS/MS experiments. We also proposed the fragmentation pathways for the studied compounds. Obtained results reveal that the ternary 12‐metallacrown‐4 formation process is not selective, and ligands of various structures and chiralities can be incorporated into these systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Headspace stir bar sorptive extraction followed by thermal desorption and gas chromatography with mass spectrometry to determine musk fragrances in sludge samples without sample pretreatment

A direct, simple and solvent‐free method based on headspace stir bar sorptive extraction and thermal desorption gas chromatography with mass spectroscopy was developed to determine 13 musk fragrances (six polycyclic musks, three nitro musks and four macrocyclic musks) in sludge without sample treatment. The optimal headspace stir bar sorptive extraction conditions were achieved when a polydimethylsiloxane stir bar was exposed for 45 min in the headspace of a 10 mL vial filled with 100 mg of sludge mixed with 0.2 mL of water stirred at 750 rpm at 80°C. The stir bar was then desorbed in the thermal desorption gas chromatography and mass spectrometry system, obtaining limits of detection between 5 and 30 ng/g. The method applicability was tested with sewage sludge from two urban wastewater treatment plants and from a potable water treatment plant. Results showed galaxolide and tonalide to be the most abundant musk fragrances found in wastewater treatment plants with maximal concentrations of 9240 and 7500 ng/g, respectively. Maximum concentration levels between 35 and 635 ng/g were found for musk ketone, musk moskene, traseolide, phantolide and celestolide in this kind of samples. Concentrations below the limits of quantitation of phantolide, galaxolide, tonalide and musk ketone were found in sludge from a potable water treatment plant.