Effect of ultrasound on the growth striation and electrical properties of Ga<Subscript>0.03</Subscript>In<Subscript>0.97</Subscript>Sb single crystals

The growth striation of impurity segregation and electrical properties of Ga_0.03In_0.97Sb single crystals grown by the Czochralski method in an ultrasonic field have been investigated. It is established that ultrasonic irradiation of the melt during growth significantly decreases the growth striation (in particular, it eliminates striations spaced at a distance of more than 14 μm). The Ga_0.03In_0.97Sb single crystals grown in an ultrasonic field had a higher charge-carrier mobility and thermoelectric power in comparison with the single crystals grown without ultrasound.     

Hydrazine hydrate: A new reagent for Fmoc group removal in solid phase peptide synthesis

In solid-phase peptide synthesis using the Fmoc/tBu strategy (SPPS-Fmoc/tBu), an orthogonal protection scheme of amino acids is used; specifically, the alpha-amine group is protected by the 9-fluorenylmethyloxycarbonyl (Fmoc) group, which is removed by weak bases, while side chains are protected by groups that are acid labile. We demonstrated that hydrazine hydrate is an efficient reagent for eliminating the Fmoc group in SPPS-Fmoc/tBu. First, experimental conditions were established for Fmoc group removal from Fmoc-Val-OH in solution. It was determined that the Fmoc group was completely removed with 16% hydrazine hydrate in DMF after 60?min at rt. Second, SPPS-Fmoc/tBu using hydrazine hydrate for Fmoc group removal was standardized. The Fmoc group removal was completed using 16% hydrazine hydrate in DMF for 10?min at rt (twice). When the reaction of Fmoc group removal was microwave-assisted, the reaction only required 30?s to efficiently remove the Fmoc group in SPPS-Fmoc/tBu. The method reported here can be routinely used, and it is equivalent to conventional SPPS-Fmoc/tBu methodologies where 4-methylpiperidine or piperidine is used.     

Phloxine B as a probe for entrapment in microcrystalline cellulose

The photophysical behaviour of phloxine B adsorbed onto microcrystalline cellulose was evaluated by reflectance spectroscopy and laser induced time-resolved luminescence in the picosecond-nanosecond and microsecond-millisecond ranges. Analysis of the absorption spectral changes with concentration points to a small tendency of the dye to aggregate in the range of concentrations under study. Prompt fluorescence, phosphorescence and delayed fluorescence spectral decays were measured at room temperature and 77 K, without the need of sample degassing because cellulose protects triplet states from oxygen quenching. In all cases, spectral changes with time and lifetime distribution analysis were consistent with the dye coexisting in two different environments: dyes tightly entrapped between polymer chains in crystalline regions of cellulose showed longer fluorescence and phosphorescence lifetimes and more energetic triplet states, while dyes adsorbed in more amorphous regions of the support showed shorter lifetimes and less energetic triplet states. This behaviour is discussed in terms of the different dye-support interactions in both kinds of adsorption sites.     

Molybdenum(VI) catalysts obtained from η3-allyl dicarbonyl precursors: synthesis, characterization and catalytic performance in cyclooctene epoxidation

The oxidative decarbonylation of the η(3)-allyl dicarbonyl complexes [Mo(η(3)-C(3)H(5))Cl(CO)(2)(L)] (L = 2,2'-bipyridine (bipy) (1), 4,4'-di-tert-butyl-2,2'-bipyridine (di-tBu-bipy) (2)) by reaction with aqueous tert-butylhydroperoxide (TBHP) or H(2)O(2) gave the following compounds in good to excellent yields: the oxo-bridged dimers [MoO(2)Cl(L)](2)O (L = bipy (3), di-tBu-bipy (6)) using TBHP(10 equiv.)/CH(3)CN/r.t.; the molybdenum oxide/bipyridine hybrid material {[MoO(3)(bipy)][MoO(3)(H(2)O)]}(n) (4) and the octanuclear complex [Mo(8)O(24)(di-tBu-bipy)(4)] (7) using TBHP(50 equiv.)/H(2)O/70 °C; the oxodiperoxo complexes MoO(O(2))(2)(L) (L = bipy (5), di-tBu-bipy (8)) using H(2)O(2)(10 equiv.)/CH(3)CN/r.t. The structure of 7·x(solvent) (where solvent = CH(2)Cl(2) and/or diethyl ether) was determined by single crystal X-ray diffraction. Despite possessing the same windmill-type complex as that described previously for 7·10CH(2)Cl(2), the crystal structure of 7·x(solvent) is unique due to differences in the crystal packing. Compounds 1-8 were examined as catalysts or catalyst precursors for the epoxidation of cyclooctene using aqueous TBHP or H(2)O(2) as oxidant at 55 or 70 °C. Reactions were performed without co-solvent or with the addition of water, ethanol or acetonitrile. Cyclooctene oxide was always the only reaction product. Solids recovered after 24 h reaction at 70 °C were identified by FT-IR spectroscopy as the hybrid 4 from (1,3-5)/TBHP, complex 5 from (1,3-5)/H(2)O(2), and complex 8 from (2,6-8)/H(2)O(2). With TBHP as oxidant, the highest epoxide yields (for 24 h reaction at 70 °C) were obtained using excess H(2)O as solvent (28-38% for 1,3-5; 87-98% for 2,6-8), while with H(2)O(2) as oxidant, the highest epoxide yields were obtained using CH(3)CN as solvent (54-81% for 3-8).     

Mitochondrially Targeted Nanoparticles Based on α‐TOS for the Selective Cancer Treatment

The aim of this work is the preparation of an active nanovehicle for the effective administration of α‐tocopheryl succinate (α‐TOS). α‐TOS is loaded in the core of nanoparticles (NPs) based on amphiphilic pseudo‐block copolymers of N‐vinyl pyrrolidone and a methacrylic derivative of α‐TOS. These well‐defined spherical NPs have sizes below 165 nm and high encapsulation efficiencies. In vitro activity of NPs is tested in hypopharynx squamous carcinoma (FaDu) cells and nonmalignant epithelial cells, demonstrating that the presence of additional α‐TOS significantly enhances its antiproliferative activity; however, a range of selective concentrations is observed. These NPs induce apoptosis of FaDu cells by activating the mitochondria death pathway (via caspase‐9). Both loaded and unloaded NPs act via complex II and produce high levels of reactive oxygen species that trigger apoptosis. Additionally, these NPs effectively suppress the vascular endothelial growth factor (VEGF) expression of human umbilical vein endothelial cells (HUVECs). These results open the possibility to use this promising nanoformulation as an α‐TOS delivery system for the effective cancer treatment, effectively resolving the current limitations of free α‐TOS administration.

     

Structural determination of the novel fragmentation routes of morphine opiate receptor antagonists using electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Electrospray ionization quadrupole time-of-flight (ESI-QqToF) mass spectra of naltrindole hydrochloride 1, naltriben mesylate 2, and naltrexone hydrochloride 3, a common series of morphine opiate receptor antagonists, were recorded using different declustering potentials. Low-energy collision-induced dissociation (CID) MS/MS experiments established the fragmentation routes of these compounds. In addition, re-confirmation of the various established fragmentation routes was effected by conducting a series of ESI-CID-QqTof-MS/MS experiments using non-conventional quasi MS(n) (up to MS8) product ion scans, which were initiated by CID in the atmospheric pressure/vacuum interface using a higher declustering potential. Precursor ion scan analyses were also performed with a conventional quadrupole-hexapole-quadrupole tandem mass spectrometer and allowed the confirmation of the genesis of some diagnostic ions.     

Dispersive solid-phase extraction based on oleic acid-coated magnetic nanoparticles followed by gas chromatography-mass spectrometry for UV-filter determination in water samples

A sensitive analytical method to concentrate and determine extensively used UV filters in cosmetic products at (ultra)trace levels in water samples is presented. The method is based on a sample treatment using dispersive solid-phase extraction (dSPE) with laboratory-made chemisorbed oleic acid-coated cobalt ferrite (CoFe(2)O(4)@oleic acid) magnetic nanoparticles (MNPs) as optimized sorbent for the target analytes. The variables involved in dSPE were studied and optimized in terms of sensitivity, and the optimum conditions were: mass of sorbent, 100mg; donor phase volume, 75 mL; pH, 3; and sodium chloride concentration, 30% (w/v). After dSPE, the MNPs were eluted twice with 1.5 mL of hexane, and then the eluates were evaporated to dryness and reconstituted with 50 μL of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) for the injection into the gas chromatography-mass spectrometry (GC-MS). Under the optimized experimental conditions the method provided good levels of repeatability with relative standard deviations below 16% (n=5, at 100 ng L(-1) level). Limit of detection values ranged between 0.2 and 6.0 ng L(-1), due to the high enrichment factors achieved (i.e., 453-748). Finally, the proposed method was applied to the analysis of water samples of different origin (tap, river and sea). Recovery values showed that the matrices under consideration do not significantly affect the extraction process.     

Indenyl ring slippage in crown thioether complexes [IndMo(CO)2L]+ and C-S activation of trithiacyclononane: experimental and theoretical studies

The macrocycle 1,4,7-trithiacyclononane (ttcn) reacts with [(η(5)-Ind)Mo(CO)(2)(NCMe)(2)](+) (or [(η(5)-Ind)Mo(CO)(2)(κ(2)-dme)](+)) to give [(η(3)-Ind)Mo(CO)(2)(κ(3)-ttcn)](+) as the BF(4)(-) salt (1), but its reaction with [(η(5)-Ind)Mo(CO)(2)(C(3)H(6))(FBF(3))] affords the C-S bond cleavage product [(η(5)-Ind)Mo(CO)(κ(3)-1,4,7-trithiaheptanate)]BF(4) (6), which has been characterised by X-ray crystallography (Ind = C(9)H(7), indenyl). In contrast to ttcn, the macrocycles 1,3,5-trithiane (tt) and 1,4,7,10-tetrathiacyclododecane (ttcd) fail to induce changes in the coordination mode of indenyl: tt and ttcd react with [(η(5)-Ind)Mo(CO)(2)(NCMe)(2)](+) (or [(η(5)-Ind)Mo(CO)(2)(κ(2)-dme)](+)) to give [(η(5)-Ind)Mo(CO)(2)(κ(2)-tt)](+) (2), characterised by X-ray crystallography, and [(η(5)-Ind)Mo(CO)(2)(κ(2)-ttcd)](+) (3), respectively. The cyclopentadienyl (Cp = C(5)H(5)) analogues [(η(5)-CpMo(CO)(2)(κ(2)-tt)](+) (4) and [(η(5)-CpMo(CO)(2)(κ(2)-ttcn)](+) (5) have also been synthesised and 5 characterised by X-ray crystallography. DFT calculations showed that the η(5)-Ind/Cp coordination mode is always the most stable. However, a molecular dynamics study of the macrocycles conformations revealed that the major conformer of ttcn was a chair, which favoured κ(3) coordination. As indenyl complexes undergo slippage with a small barrier (<10 kcal mol(-1)), the kinetically preferred species [(η(3)-Ind)Mo(CO)(2)(κ(3)-ttcn)](+) (1) is the observed one. The conversion to 6 proceeds stepwise, with loss of ethylene followed by loss of CO, as calculated by DFT, with a barrier of 38.7 kcal mol(-1), consistent with the slow uncatalysed reaction.     

Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO2 hydrate equilibria

In the present work, experimental data on the equilibrium conditions of mixed CO₂ and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl₂), magnesium chloride (MgCl₂), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO₂ and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L_W), liquid organic (L_V), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid–liquid phase split of (water + THF) mixture when pressurized with CO₂ and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF < KBr < NaCl < NaBr < CaCl₂ < MgCl₂. Among the cations studied, the strength of hydrate inhibition increases in the following order: K⁺ < Na⁺ < Ca²⁺ < Mg²⁺. Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br^? > Cl^? > F^?. Based on the results, it is suggested that the probability of formation and the strength of ionic–hydrogen bond between an ion and water molecule and the effects of this bond on the ambient water network are the major factors that contribute to hydrate inhibition by electrolytes.     

Metalloenzyme‐Like Zeolites as Lewis Acid Catalysts for CC Bond Formation

The use of metalloenzyme‐like zeolites as Lewis acid catalysts for C? C bond formation reactions has received increasing attention over the past few years. In particular, the observation of direct aldol condensation reactions enabled by hydrophobic zeolites with isolated framework metal sites has encouraged the development of catalytic approaches for producing chemicals from biomass‐derived compounds. The discovery of new Diels–Alder cycloaddition/dehydration routes and experimental and computational studies of Lewis acid catalyzed carbonyl–ene reactions have given a further boost to this rapidly evolving field.