Unsaturated alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s: Synthesis and chemical–physical characterization

A new series of alkoxy‐substituted poly(p‐phenylene 1,3,4‐oxadiazole)s modified by the insertion of small percentages of various comonomers were synthesized through the precursor polyhydrazides. The comonomers used contained trans double bonds or meta‐alkoxy‐substituted aromatic rings to improve the solubility of the final polymers. The synthesized copolymers were chemically characterized by ¹H NMR and Fourier transform infrared spectroscopy. In some cases, the copolymers really showed improved solubility in organic solvents. The ¹⁵N solid‐state NMR technique was applied to examine the degree of conversion from the precursor polyhydrazides to the final polymers, which determined the effective conjugated length in the target polyoxadiazoles. Thermal stability and structural characteristics of all the polymers as well as a preliminary investigation on the optical properties of polyoxadiazoles are also reported. The copolymers retained high absorbance in the UV region and high transmission in the whole telecommunication range. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3916–3928, 2003     

Synthesis, crystal structure and magnetic properties of an oxalato-bridged Re(IV)Mo(VI) heterobimetallic complex

The Re(IV)-Mo(VI) compound of formula (PPh(4))(2)[ReCl(4)(μ-ox)MoO(2)Cl(2)] (1) constitutes the first example of a heterodinuclear oxalato-bridged complex in the coordination chemistry of molybdenum.     

Optimization and Validation of a Confirmatory Method for Determination of Ten Sulfonamides in Feeds by LC and UV-Diode Array Detection

A simple, rapid, and reliable multiresidue method, based on liquid chromatography (LC) and ultraviolet (UV)-diode array detection (DAD), is described for assaying ten sulfonamides (sulfadiazine, sulfathiazole, sulfamerazine, sulfamethazine, sulfamethoxypyridazine, sulfamonomethoxine, sulfachloropyridazine, sulfamethoxazole, sulfaquinoxaline, and sulfadimethoxine) in feeds. The chromatographic separation is accomplished using a C18 column, eluted with a mobile phase consisting of acetate buffer, acetonitrile, and methanol. The sample preparation requires a simple extraction with chloroform/acetone and a purification step by solid-phase extraction. The analytical parameters of precision, detection and quantification limits, recovery, and ruggedness have been evaluated by a validation procedure following the European guidelines of Regulation 882/2004/EC and Decision 657/2002/EC.     

Advances in the chemistry of nanosized zirconium phosphates: a new mild and quick route to the synthesis of nanocrystals

Simple addition of zirconyl propionate to phosphoric acid in alcoholic media surprisingly led to the formation, in few minutes, of transparent gels containing solvent intercalated zirconium phosphate (ZrP) nanoparticles with hexagonal shape and a planar size of about 40 nm. With the help of elemental analysis, inductively coupled plasma-optical emission spectrometry (ICP-OES), and (31)P magic angle spinning (MAS) NMR, the nanoparticle composition was formulated as Zr(R)(w)(HPO(4))(x)(H(2)PO(4))(y), in which R can be an hydroxyl or a propionate group. The stoichiometric coefficients for propanol intercalated ZrP are x = 1.43, y = 0.83, and w = 0.32. Solvent elimination at 60 °C gave rise to an increase in the x value and a decrease in the y and w values. X-ray powder diffraction analysis and transmission electron microscopy (TEM) observations showed a concomitant increase in the particle size: planar size and thickness ranged from 90 to 200 nm and from 20 to 85 nm, respectively, depending on the nature of the solvent. A possible mechanism explaining the change in the x, y, and w values, the growth of nanoparticles, and the role of the solvent is proposed. Finally, the possibility of using these gels to disperse the ZrP nanoparticles within the polymer matrix of Nafion117 is shown.     

Dual asymmetric-flow microdialysis for in vivo monitoring of brain neurochemicals

Microdialysis is an extensively used technique for both in vivo and in vitro experiments, applicable to animal and human studies. In neurosciences, the in vivo microdialysis is usually performed to follow changes in the extracellular levels of substances and to monitor neurotransmitters release in the brain of freely moving animals. Catecholamines, such as dopamine and their related compounds, are involved in the neurochemistry and in the physiology of mental diseases and neurological disorders. It is generally supposed that the brain's energy requirement is supplied by glucose oxidation. More recently, lactate was proposed to be the metabolic substrate used by neurons during synaptic activity. In our study, an innovative microdialysis approach for simultaneous monitoring of catecholamines, indolamines, glutamate and energy substrates in the striatum of freely moving rats, using an asymmetric perfusion flow rate on microdialysis probe, is described. As a result of this asymmetric perfusion, two samples are available from the same brain region, having the same analytes composition but different concentrations. The asymmetric flow perfusion could be a useful tool in neurosciences studies related to brain's energy requirement, such as toxin-induced models of Parkinson's disease.     

Hardy–Sobolev Type Inequalities with Sharp Constants in Carnot–Carathéodory Spaces

We prove a generalization with sharp constants of a classical inequality due to Hardy to Carnot groups of arbitrary step, or more general Carnot–Carathéodory spaces associated with a system of vector fields of Hörmander type. Under a suitable additional assumption (see Eq. 1.6 below) we are able to extend such result to the nonlinear case \(p\not= 2\). We also obtain a sharp inequality of Hardy–Sobolev type.     

Geochemical study of black crusts as a diagnostic tool in cultural heritage

This contribution focuses on spectrometric analyses carried out on crust samples covering the stone surface of the boundary walls of the Tower of London. The main goal of this research is to investigate the degradation processes related to the environmental impact on cultural heritage. Specifically, the chemical contamination of stone substrate in the Tower of London due to the crust formation was examined through laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This technique allowed us to achieve a complete characterization of the damage layers in terms of trace elements. In addition, optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS) and infrared spectroscopic techniques (FT-IR) were also used for an exhaustive characterization of the examined samples. Results obtained demonstrated that such a geochemical approach represents a powerful diagnostic tool in the study of black crusts, since it represents a reliable indicator of the environmental pollution. The higher concentrations of most heavy metals in black crusts with respect to the underlying stone suggest that crusts were greatly influenced by atmospheric inputs in their formation, mainly represented by mobile combustion sources. In addition, the possibility of analyzing in some samples the portion of altered substrate allowed us to hypothesize that some specific heavy metals tend to migrate from the crust to the unaltered substrate over time, becoming catalysts for the formation of new crust. Therefore, this research focuses on the role of diagnostics in order to plan suitable cleaning and consolidation intervention aimed at a better protection of the monument.     

MOF-Stabilized Perfluorinated Palladium Cages Catalyze the Additive-Free Aerobic Oxidation of Aliphatic Alcohols to Acids

Extremely high electrophilic metal complexes, composed by a metal cation and very electron poor σ-donor ancillary ligands, are expected to be privileged catalysts for oxidation reactions in organic chemistry. However, their low lifetime prevents any use in catalysis. Here we show the synthesis of fluorinated pyridine-Pd²⁺ coordinate cages within the channels of an anionic tridimensional metal-organic framework (MOF), and their use as efficient metal catalysts for the aerobic oxidation of aliphatic alcohols to carboxylic acids without any additive. Mechanistic studies strongly support that the MOF-stabilized coordination cage with perfluorinated ligands unleashes the full electrophilic potential of Pd²⁺ to dehydrogenate primary alcohols, without any base, and also to activate O₂ for the radical oxidation to the aldehyde intermediate. This study opens the door to design catalytic perfluorinated complexes for challenging organic transformations, where an extremely high electrophilic metal site is required.     

Validation of a liquid chromatography coupled with tandem mass spectrometry method for the determination of drugs in wastewater using a three‐phase solvent system

Pharmaceuticals constitute one of the most important emerging classes of environmental pollutants. A three‐phase solvent system of water, water containing 0.1% of formic acid and acetonitrile was successfully used to separate, by liquid chromatography with mass spectrometry (LC‐MS), polarity‐matched pharmaceuticals, that is, carbamazepine, clarithromycin, and erythromycin, as well as amoxicillin and metformin. Despite of polarity similarities, these pharmaceuticals were completely resolved in the analytical run time of 15 min. The optimized three‐phase solvent system based‐method was validated for the simultaneous analysis of six matched‐polarity pharmaceuticals in wastewater samples. Good linearity (coefficient of determination more than 0.993) and precision (relative standard deviation less than 15.66%) were achieved. Recovery of analytes from the wastewater was between 0.70 and 1.18. Limits of detections ranged from 0.0001 to 0.5114 µg/L. No significant matrix effect, evaluated by post extraction addition, was observed in the electrospray ionization (ESI) source. Then, this methodology has been successfully applied to environmental study of pharmaceutical residues occurring in influent and effluent wastewater samples, from the main wastewater treatment plant in Potenza (Basilicata, Southern Italy).