Tri-[Pt2Tl]3- and polynuclear chain [Pt-Tl]infinity- complexes based on nonbridged Pt(II)-Tl(I) bonds: solid state and frozen solution photophysical properties

Treatment of (NBu4)2[PtR4] (R = C6F5) with 1 or 0.5 equiv of TlNO3 in EtOH/H(2)O produces colorless crystals of trinuclear complex (NBu4)3[Tl{PtR4}2], 1, in which the Tl+ center is complexed by two [PtR4]2- fragments (Pt-Tl = 2.9777(4) and 3.0434(4) A). The expected mixed complex with a Pt/Tl composition of 1:1, 2, is generated as an orange microcrystalline solid by treating [PtR4]2- with a large excess of TlNO3 (approximately 8 equiv). Crystallographic analysis of 2 reveals the formation of a novel one-dimensional (1D) heterometallic linear chain (NBu4)(infinity)[Tl{PtR4}](infinity), 2, formed by alternating a [PtR4]2- fragment and a Tl+ center with a uniform Pt-Tl bond separation along the chain of 3.0321(2) A. Surprisingly, treatment of (NBu4)2[PtR4] with 1 equiv of TlPF6 in EtOH yields pale greenish-yellow needles of an unusual adduct, 2.{(NBu4)(PF6)}(infinity) (3), which was found to form a similar extended linear chain, {TlPtR4}(infinity), constructed by two alternating Pt-Tl separations, a shorter (3.1028(6) A) one and a longer (3.2306(6) A) one. The solid state and solution photophysical properties have been examined. While complex 1 shows a high-energy MM'CT blue phosphorescence (450 nm), the extended chain in 2 exhibits a lower-energy emission (582 nm) than that in adduct 3 (505 nm). For products 2 and 3, interesting luminescence thermochromism is observed in frozen solutions. The emissions are found to be strongly dependent on the solvent, concentration, and excitation wavelength.     

Synthesis,characterization and crystal structure of the new pentahydrate of bis(2,2′‐bipyridine‐κ2N,N′)(oxalato‐κ2O1,O2)nickel(II)

The reaction of NiCl₂, K₂C₂O₄·H₂O and 2,2′‐bipyridine (bpy) in water–ethanol solution at 281 K yields light‐purple needles of the new pentahydrate of bis(2,2′‐bipyridine)oxalatonickel(II), [Ni(C₂O₄)(C₁₀H₈N₂)₂]·5H₂O or [Ni(ox)(bpy)₂]·5H₂O, while at room temperature, deep‐pink prisms of the previously reported tetrahydrate [Ni(ox)(bpy)₂]·4H₂O [Román, Luque, Guzmán‐Miralles & Beitia (1995), Polyhedron, 14 , 2863–2869] were gathered. The asymmetric unit in the crystal structure of the new pentahydrate incorporates the discrete molecular complex [Ni(ox)(bpy)₂] and five solvent water molecules. Within the complex molecule, all three ligands are bonded as chelates. The complex molecules are involved in an extended system of hydrogen bonds with the solvent water molecules. Additionally, π–π interactions also contribute to the stabilization of the extended structure. The dehydration of the pentahydrate starts at 323 K and proceeds in at least two steps as determined by thermal analysis.     

On-line Chloride Interference Removal for Arsenic Determination in Waste Water and Urine by ICP-MS Using a Modified Capillary

The determination of arsenic in environmental samples like waste waters from industrial effluents and in biological samples like urine is very important due to the toxic nature of some of its species at moderate levels of exposure. The objective of this study was to evaluate the capability of modified anionic capillaries to remove chloride for ICP-MS determination of arsenic, which causes spectral interference due to formation of 40 Ar 35 Cl + . Also high chloride content gives non-spectral interferences. The results indicate that arsenic at a concentration higher than 1 µg L m 1 in a matrix with a chloride content up to 600 mg L m 1 can be accurately determined using a 3-aminopropyltrimethoxysilane (APTMS) modified capillary connected to a microconcentric nebuliser (MCN). The interference level of chloride is considerably reduced due to its retention in the capillary. The method has been successfully applied and validated for waste water and by recovery tests for urine (diluted 1 : 15) samples.     

Novel naphthalimide–aminobenzamide dyads as OFF/ON fluorescent supramolecular receptors in metal ion binding

A series of novel naphthalimide–aminobenzamide (NAPIM-2ABZ) dyads 3 connected by different length polymethylene chains were synthesized and studied as fluorescent supramolecular receptors in metal ion binding. The photophysical properties were evaluated and compared with separated chromophores. The electronic absorption spectra of dyads 3 showed no interaction between chromophores in the ground state. The fluorescence quantum yields were lower in dyads 3 in comparison with N-propyl-2-aminobenzamide (8). The fluorescence quenching is attributed to a PET mechanism between fluorophores (from 2ABZ to NAPIM), which is dependent on the polymethylene chain length. In metal binding study was found a response towards transition metal ions such as Hg(II), Cu(II), Zn(II) and Ni(II). Dyad 3b presented selectivity towards Cu(II). The UV-vis, IR and ¹H-NMR studies demonstrated the interaction with 2ABZ moiety in the ground state, and interestingly dyads with shorter polymethylene chains 3a (n = 0), 3b (n = 1) and 3c (n = 2) exhibited an OFF/ON fluorescence behaviour due to the PET inhibition and the quenching of 2ABZ fluorescence. Dyads 3d (n = 4) and 3e (n = 6) presented opposite response ON/OFF in the complex with metal ions evidencing the absence of PET in these dyads.     

Strategies for the Biofunctionalization of Straining Flow Spinning Regenerated Bombyx mori Fibers

High-performance regenerated silkworm (Bombyx mori) silk fibers can be produced efficiently through the straining flow spinning (SFS) technique. In addition to an enhanced biocompatibility that results from the removal of contaminants during the processing of the material, regenerated silk fibers may be functionalized conveniently by using a range of different strategies. In this work, the possibility of implementing various functionalization techniques is explored, including the production of fluorescent fibers that may be tracked when implanted, the combination of the fibers with enzymes to yield fibers with catalytic properties, and the functionalization of the fibers with cell-adhesion motifs to modulate the adherence of different cell lineages to the material. When considered globally, all these techniques are a strong indication not only of the high versatility offered by the functionalization of regenerated fibers in terms of the different chemistries that can be employed, but also on the wide range of applications that can be covered with these functionalized fibers.     

Preparation of side‐chain liquid crystalline Azopolymers by CuAAC postfunctionalization using bifunctional azides: Induction of chirality using circularly polarized light

Well‐defined side‐chain liquid crystal azopolymers have been synthesized by click chemistry of poly(propargyl methacrylate) with bifunctional liquid crystalline azides to produce materials with large degrees of functionalization. A polymeric scaffold having pendant alkyne groups was prepared by atom transfer radical polymerization (ATRP) and postfunctionalized by copper(I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) using homo‐ and heterobifunctional azides. The azides are derivatives of 2,2‐bis(hydroxymethyl)propanoic acid (bis‐MPA) containing photoresponsive azobenzene and/or liquid crystalline biphenyl moieties. The approach is a convenient alternative to increase the density of functional units in side‐chain polymers having moderate polymerization degrees and to modulate the properties of the final material. The article describes the synthesis, characterization, and liquid crystalline properties of the obtained polymers. The effect of the chemical structure and the possible cooperative effects between functional units in the photo‐induction of chirality are also evaluated. A switchable photo‐transference of chirality from the circularly polarized light (CPL) to material has been achieved. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Pressurized liquid extraction as a sample preparation method for the analysis of isoflavones in pulses

In this work, we describe a rapid and simple analytical method that exploits pressurized liquid extraction (PLE) and liquid chromatography with diode array detection for the determination of isoflavones in samples of Spanish pulses. Confirmation of the analytes present was performed using ion-trap mass spectrometry. To optimize the PLE extraction, variables such as the dispersing agent, type of solvent and sample amount, and the experimental parameters, such as temperature and the number of extraction cycles, were studied. Separation was carried out using a reverse-phase C18 with polar endcapping as the stationary phase and acetonitrile/water with 0.2?% of formic acid, under a gradient regime, as the mobile phase. Optimal extraction of formononetin and biochanin-A from chickpeas with PLE was achieved using Hydromatrix as a dispersant agent, methanol/water (50:50), a temperature of 90?°C, and three cycles. The same optimal conditions-except methanol/water (75:25)-for solvent extraction were obtained for the extraction of daidzin, genistin, and formononetin from lentils. Recoveries ranged from 97 to 110?%, and standard deviations lower than 20?% were obtained. The contents obtained for daidzin in lentils using the proposed method were not significantly different from those obtained using another official method of analysis.     

Liquid chromatography/time-of-flight mass spectrometric analyses for the elucidation of the photodegradation products of triclosan in wastewater samples

Liquid chromatography coupled with time-of-flight mass spectrometry (LC/TOFMS) was applied for the identification of four new photodegradation products of triclosan, a major antimicrobial agent used in personal care products. Wastewater samples, spiked at 7 microg/mL with triclosan, were irradiated with natural sunlight in order to generate the photodegradation products. Aliquots of the spiked water samples were taken at different times of irradiation and compounds were isolated from the water samples by solid-phase extraction. Separation and detection of the compounds and degradation products were accomplished by LC/TOFMS, which provided highly selective information about elemental compositions. Accurate mass measurements for the four degradation products permitted postulation of proposed empirical formulae in this study. Replacement of chlorine atoms by hydroxyl groups and chlorine losses are the major degradation pathways proposed. The degradation products were formed also under environmental conditions in wastewater matrices, thus suggesting their presence in real wastewater treatment processes.