A supramolecular copper(II) compound with double bridging water ligands: synthesis, crystal structure, spectroscopy, thermal analysis, and magnetism

A complex of composition {[{Cu(NDC)(OH₂)(tn)(μ-OH₂)}₂]·2H₂O}_∞ (1) and a mononuclear complex salt [Cu(OH₂)₂(tn)₂](NDC)·3H₂O (2), where NDC = 2,6-naphthalenedicarboxylate dianion and tn = 1,3-diaminopropane, were simultaneously crystallized from an aqueous solution of the copper(II) naphthalenedicarboxylate—1,3-diaminopropane—methanol system. The crystal and molecular structures of both complexes were determined by single-crystal X-ray diffraction. Compound (1) consists of a supramolecular coordination complex in which the monomeric unit is assembled from a homodinuclear Cu(II) bridged by two water ligands. The Cu(II) centers exhibit distorted octahedral coordination; the equatorial plane is provided by one chelating tn ligand, one NDC^2? ligand, one μ-H₂O while the axial positions are occupied by H₂O and μ-H₂O. Strong intra- and/or intermolecular hydrogen bonds, also involving the crystallization water molecules, together with π–π stacking interactions, are involved in building up the supramolecule. The solid structure of compound (2) includes three water molecules of crystallization, the counter ion NDC^2?, and a Cu(II) cationic complex in which the metal is six-coordinated in an axially elongated octahedron defined by two chelating tn ligands in the equatorial plane and two water ligands in the axial positions. Thermal analyses of (1) show two significant weight losses corresponding to water molecules (lattice and coordinated), followed by the decomposition of the network.     

Scaling properties of the Miesowicz coefficients

In this work a set of experimental data points is used to study some scaling properties of Miesowicz coefficients. Using the fact that all the compounds studied present two critical points—the crystal–nematic and the nematic–isotropic phase transitions—a common temperature scale was defined. With the use of this unique temperature scale two relevant aspects that distinguish the viscosity of these materials can be simultaneously extracted and studied: (1) the molecular shape anisotropy and (2) the different strengths of molecular interaction of the different compounds. Through the study of the scaling properties associated with these properties, the existence of a common law connecting the Miesowicz coefficients with the associated decay time is proposed.     

Use of two different coating temperatures for a cold fiber headspace solid‐phase microextraction system to determine the volatile profile of Brazilian medicinal herbs

In this study, the experimental extraction conditions on applying headspace solid‐phase microextraction and cold fiber headspace solid‐phase microextraction (CF‐HS‐SPME) procedures to samples of six medicinal herbs commonly found in southern Brazil were optimized. The optimized conditions for headspace solid‐phase microextraction were found to be an extraction temperature of 60°C and extraction time of 40 min. For CF‐HS‐SPME, the corresponding values were 60°C and 15 min. In the case of the coating temperature for the CF‐HS‐SPME system, two approaches were investigated: (i) Temperature of 5°C applied during the whole extraction procedure; and (ii) the use of two fiber temperatures in the same extraction procedure with the aim of extracting the volatile and semivolatile compounds, the ideal condition being 60°C for the first 7.5 min and 5°C for the final 7.5 min. The three extraction procedures were compared. The CF‐HS‐SPME procedure had good performance only for the more volatile compounds whereas the strategy using two coating temperatures in the same procedure showed good performance for all compounds studied. It was also possible to determine the profile for the volatile fraction of each herb studied applying this technique followed by GC‐MS.     

Determination of 48 pesticides and their main metabolites in water samples by employing sonication and liquid chromatography-tandem mass spectrometry

In this work, a rapid and sensitive analytical multiresidue method has been developed for the simultaneous determination of 48 pesticides and 19 metabolites in waters (tap, leaching and sewage), using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with triple quadrupole in selected reaction monitoring (SRM) mode. The procedure involves initial single phase extraction of samples with acetonitrile by sonication, followed by liquid-liquid partition aided by “salting out” process using NaCl. Matrix influence on recoveries was evaluated for the three waters. More than 50% of the compound presented very low signal suppression. The method presents good linearity over the range assayed 10-500 μg L⁻¹ and the most frequent detection limits was 0.05 ng mL⁻¹. The average recovery by the LC-MS/MS method obtained for these compounds varied from 74.6 to 111.2% with a relative standard deviation between 2.5 and 8.9%. The proposed method was used to determine pesticides levels in leaching water samples from 5 lysimeters from an experimental greenhouse located in Murcia.     

Ultrathin zirconium disulfide nanodiscs

We present a colloidal route for the synthesis of ultrathin ZrS(2) (UT-ZrS(2)) nanodiscs that are ~1.6 nm thick and consist of approximately two unit cells of S-Zr-S. The lateral size of the discs can be tuned to 20, 35, or 60 nm while their thickness is kept constant. Under the appropriate conditions, these individual discs can self-assemble into face-to-face-stacked structures containing multiple discs. Because the S-Zr-S layers within individual discs are held together by weak van der Waals interactions, each UT-ZrS(2) disc provides spaces that can serve as host sites for intercalation. When we tested UT-ZrS(2) discs as anodic materials for Li(+) intercalation, they showed excellent nanoscale size effects, enhancing the discharge capacity by 230% and greatly improving the stability in comparison with bulk ZrS(2). The nanoscale size effect was especially prominent for their performance in fast charging/discharging cycles, where an 88% average recovery of reversible capacity was observed for UT-ZrS(2) discs with a lateral diameter of 20 nm. The nanoscale thickness and lateral size of UT-ZrS(2) discs are critical for fast and reliable intercalation cycling because those dimensions both increase the surface area and provide open edges that enhance the diffusion kinetics for guest molecules.     

Optimization of the ultrasound-assisted synthesis of allyl 1-naphthyl ether using response surface methodology

Allyl 1-naphthyl ethers are useful compounds for different purposes, but reported methods to synthesize them require long reaction times. In this work, we have obtained allyl 1-naphthyl ether in good yield using ultrasonic-assisted methodology in a 1-h reaction. A central composite design was used to obtain a statistical model and a response surface (p<0.05; R(2)=0.970; R(2)(adj)=0.949; R(2)(pred)=0.818) that can predict the optimal conditions to maximize the yield, validated experimentally.     

Evaluation of DNA damage and cytotoxicity of polyurethane-based nano- and microparticles as promising biomaterials for drug delivery systems

The in vitro cytotoxicity and DNA damage evaluation of biodegradable polyurethane-based micro- and nanoparticles were carried out on animal fibroblasts. For cytotoxicity measurement and primary DNA damage evaluation, MTT and Comet assays were used, respectively. Different formulations were tested to evaluate the influence of chemical composition and physicochemical characteristics of particles on cell toxicity. No inhibition of cells growth surrounding the polyurethane particles was observed. On the other hand, a decrease of cell viability was verified when the anionic surfactant sodium dodecyl sulfate (SDS) was used as droplets stabilizer of monomeric phase. Polyurethane nanoparticles stabilized with Tween 80 and Pluronic F68 caused minor cytotoxic effects. These results indicated that the surface charge plays an important role on cytotoxicity. Particles synthesized from MDI displayed a higher cytotoxicity than those synthesized from IPDI. Size and physicochemical properties of the particles may explain the higher degree of DNA damage produced by two tested formulations. In this way, a rational choice of particles’ constituents based on their cytotoxicity and genotoxicity could be very useful for conceiving biomaterials to be used as drug delivering systems.     

Vinyl Halide-Modified Unsaturated Cyclitols are Mechanism-Based Glycosidase Inhibitors

Suitably configured allyl ethers of unsaturated cyclitols act as substrates of β-glycosidases, reacting via allylic cation transition states. Incorporation of halogens at the vinylic position of these carbasugars, along with an activated leaving group, generates potent inactivators of β-glycosidases. Enzymatic turnover of these halogenated cyclitols (F, Cl, Br) displayed a counter-intuitive trend wherein the most electronegative substituents yielded the most labile pseudo-glycosidic linkages. Structures of complexes with the Sulfolobus β-glucosidase revealed similar enzyme-ligand interactions to those seen in complexes with a 2-fluorosugar inhibitor, the lone exception being displacement of tyrosine 322 from the active site by the halogen. Mutation of Y322 to Y322F largely abolished glycosidase activity, consistent with lost interactions at O5, but minimally affected (7-fold) rates of carbasugar hydrolysis, yielding a more selective enzyme for unsaturated cyclitol ether hydrolysis.