Three 4,7‐diaryl‐2‐ethylsulfanylpyrazolo[1,5‐a][1,3,5]triazines

The molecular dimensions of 2‐ethylsulfanyl‐7‐(4‐methylphenyl)‐4‐phenylpyrazolo[1,5‐a][1,3,5]triazine, C₂₀H₁₈N₄S, (I), 7‐(4‐chlorophenyl)‐2‐ethylsulfanyl‐4‐phenylpyrazolo[1,5‐a][1,3,5]triazine, C₁₉H₁₅ClN₄S, (II), and 4,7‐bis(4‐chlorophenyl)‐2‐(ethylsulfanyl)pyrazolo[1,5‐a][1,3,5]triazine, C₁₉H₁₄Cl₂N₄S, (III), show evidence for some aromatic delocalization in the pyrazole rings. The conformations adopted by the ethylsulfanyl substituents are different in all three compounds. There are no hydrogen bonds in any of the crystal structures, but pairs of molecules in (II) and (III) are linked into centrosymmetric dimers by π‐stacking interactions.     

Thermal behavior of some new triazole derivative complexes

A series of new complexes with mixed ligands of the type [ML(C₃H₃O₂)₂]·nH₂O (((1) M=Mn, n=1; (2) M=Co(II), n=2; (3) M=Ni(II), n=4; (4) M=Cu(II), n=1.5; (5) M=Zn(II), n=0; L=3-amino-1,2,4-triazole and (C₃H₃O₂)=acrylate anion) were synthesized and characterised by chemical analysis and IR data. In all complexes the 3-amino-1,2,4-triazole acts as bridge while the acrylate acts as bidentate ligand except for complex (5) where it is found as unidentate. The thermal behaviour steps were investigated in nitrogen flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion and 3-amino-1,2,4-triazole degradation respectively. The final products of decomposition are the most stable metal oxides, except for complex (4) that leads to metallic copper.     

Simultaneous profiling of multiple neurochemical pathways from a single cerebrospinal fluid sample using GC/MS/MS with electron capture detection

Biogenic amines and amino acids are widely characterized in the pathways representing neurotransmission. Although several analytical methodologies have been used to detect specific target molecules in relevant fluids such as cerebrospinal fluid (CSF), multiple assays must be used to survey the primary pathways involved. This article describes the development of a GC/MS/MS method capable of analyzing up to 43 analytes (representing 20 amino acids and more than seven neurochemical pathways) from a single 50 microl CSF sample. In this procedure, a CSF sample is first treated with acetonitrile to precipitate proteins. The dried sample is then derivatized with a mixture of 2,2,3,3,3-pentafluoro-1-propanol and pentafluoropropionic acetic anhydride to replace all active hydrogen atoms with fluorine-containing groups. Due to the concentration difference between amino acids and neurotransmitters, these two compound classes are analyzed in separate injections of the same derivatized extract. The total run time for each injection is approximately 15-20 min. An essential feature of the method is the use of argon as a reagent gas for electron capture chemical ionization (ECCI), as the use of the more traditional gas (methane) lacked sufficient durability to be considered for use with the present instrumentation. This article describes the development of this method including a detailed investigation of the chemical ionization conditions used. The resultant conditions allow for the profiling of biogenic amines (e.g. serotonin, norepinephrine, and dopamine) in the low picogram per milliliter range.     

Confinement-Driven Photophysics in Hydrazone-Based Hierarchical Materials

Confinement-imposed photophysics was probed for novel stimuli-responsive hydrazone-based compounds demonstrating a conceptual difference in their behavior within 2D versus 3D porous matrices for the first time. The challenges associated with photoswitch isomerization arising from host interactions with photochromic compounds in 2D scaffolds could be overcome in 3D materials. Solution-like photoisomerization rate constants were realized for sterically demanding hydrazone derivatives in the solid state through their coordinative immobilization in 3D scaffolds. According to steady-state and time-resolved photophysical measurements and theoretical modeling, this approach provides access to hydrazone-based materials with fast photoisomerization kinetics in the solid state. Fast isomerization of integrated hydrazone derivatives allows for probing and tailoring resonance energy transfer (ET) processes as a function of excitation wavelength, providing a novel pathway for ET modulation.     

In-channel atom-transfer radical polymerization of thermoset polyester microfluidic devices for bioanalytical applications

A new technique for polymer microchannel surface modification, called in-channel atom-transfer radical polymerization, has been developed and applied in the surface derivatization of thermoset polyester (TPE) microdevices with poly(ethylene glycol) (PEG). X-ray photoelectron spectroscopy, electroosmotic flow (EOF), and contact angle measurements indicate that PEG has been grafted on the TPE surface. Moreover, PEG-modified microchannels have much lower and more pH-stable EOF, more hydrophilic surfaces and reduced nonspecific protein adsorption. Capillary electrophoresis separation of amino acid and peptide mixtures in these PEG-modified TPE microchips had good reproducibility. Phosducin-like protein and phosphorylated phosducin-like protein were also separated to measure the phosphorylation efficiency. Our results indicate that PEG-grafted TPE microchips have broad potential application in biomolecular analysis.     

Resistance to sulfur poisoning of Rh supported catalysts

Sulfur thiotolerance by thiophene during toluene hydrogenation on rhodium supported catalysts prepared on different supports and metal precursors have been studied. The catalysts were characterized by H₂ chemisorption, TEM, TPD of ammonia and XPS. The turnover frequency of the reaction does not change significantly with the carrier but in the presence of 10 ppm of thiophene a drastic decrease in the activity is observed. The initial deactivation constant follows the order Rh/SiO₂>Rh/TiO₂>Rh/Al₂O₃.     

Q-shear transformation for MQMAS and STMAS NMR spectra

The multiple-quantum magic-angle spinning (MQMAS) and satellite-transition magic-angle spinning (STMAS) experiments refocus second-order quadrupolar broadening of half-integer quadrupolar spins in the form of two-dimensional experiments. Isotropic shearing is usually applied along the indirect dimension of the 2D spectra such that an isotropic projection free of anisotropic quadrupolar broadening can be obtained. An alternative shear transformation by a factor equal to the coherence level (quantum number) selected during the evolution period is proposed. Such a transformation eliminates chemical shift along the indirect dimension leaving only the second-order quadrupolar-induced shift and anisotropic broadening, and is expected to be particularly useful for disordered systems. This transformation, dubbed Q-shearing, can help avoid aliasing problems due to large chemical shift ranges and spinning sidebands. It can also be used as an intermediate step to the isotropic representation for expanding the spectral window of rotor-synchronized experiments.     

Leptogorgolide, a biogenetically interesting 1,4-diketo-cembranoid that reinforces the oxidation profile of C-18 as taxonomical marker for octocorals

The cembranoid 1 and the furanocembranolides 2-4 along with the known pukalide were isolated from Leptogorgia sp. and their structures determined spectroscopically. The 1,4-diketo-cembranoid 1 follows an oxidation pattern of C-18 that reinforces the concept of oxidation profile of C-18 as taxonomical marker for octocorals. The co-occurrence within a species of furanocembranolide/1,4-diketo-cembranoid congeners 1/2-4 raises the question about which one is the biogenetic precursor. A biogenetic pathway is proposed.     

The neutral cluster amminehexa‐μ2‐chlorido‐μ4‐oxido‐tris(1,4,6‐triazabicyclo[3.3.0]oct‐4‐ene)tetracopper(II)

The title compound, [Cu₄Cl₆O(C₅H₉N₃)₃(NH₃)], is a neutral conformationally chiral cluster which crystallizes under the conditions described in this paper as a racemic conglomerate. It contains four Cu^II atoms in a tetrahedral coordination with a central O atom lying on a crystallographic threefold axis. Six chloride anions bridge the four Cu^II atoms. Three Cu^II atoms are bound by an N atom of a monodentate 1,4,6‐triazabicyclo[3.3.0]oct‐4‐ene (Htbo) ligand and the remaining Cu^II atom is bound by a terminal ammine ligand. The geometry at each copper center is trigonal bipyramidal, produced by the bound N atom of Htbo or ammonia, the O atom in the axial position, and three chloride ions in the equatorial plane. The chloride anions form an octahedron about the oxygen center. The copper–ammonia bond lies along the crystallographic threefold axis, along which the molecules are packed in a polar head‐to‐tail fashion.