Ethyl β‐{2‐[4‐(dimethylamino)phenyliminomethyl]‐1‐(phenylsulfonyl)indol‐3‐yl}acrylate

The title compound, C₂₈H₂₇N₃O₄S, crystallizes in the centrosymmetric space group P2₁/n, with one mol­ecule in the asymmetric unit. In the indole ring, the dihedral angle between the fused rings is 3.6 (1)°. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 79.2 (1)° with the best plane of the indole moiety. The phenyl ring of the di­methyl­amino­phenyl group is orthogonal to the phenyl ring of the phenyl­sulfonyl group. The dihedral angle formed by the weighted least‐squares planes through the pyrrole ring and the phenyl ring of the di­methyl­amino­phenyl group is 7.8 (1)°. The molecular structure is stabilized by C—H?O and C—H?N interactions.     

Synthesis, structure, and photocatalysis in a new structural variant of the Aurivillius phase: LiBi4M3O14 (M = Nb, Ta)

Two new compounds, LiBi4Nb3O14 and LiBi4Ta3O14, have been synthesized by the solid-state method, using Li2CO3, Bi2O3, and M2O5 (M = Nb, Ta) in stoichiometric quantities. These compounds crystallize in the monoclinic C2/c space group with a = 13.035(3) A, b = 7.647(2) A, c = 12.217(3) A, beta = 101.512(4) degrees , V = 1193.4(5) A3 , and Z = 4 and a = 13.016(2) A, b = 7.583(1) A, c = 12.226(2) A, beta = 101.477(3) degrees , V = 1182.6(5) A3, and Z = 4, respectively. These are isostructural and the structure along the b axis consists of layers of [Bi2O2]2+ units separated by layers of LiO4 tetrahedra and NbO6 octahedra hence depicting an unusual variation in the Aurivillius phase isolated for the first time. The presence of lithium has been confirmed by 7Li NMR studies. ac impedance measurements and variable temperature (7)Li NMR studies indicate oxygen ion conductivity in these materials. The UV-visible spectra suggest a band gap of 3.0 eV for LiBi4Nb3O14 and 3.5 eV for LiBi4Ta3O14, respectively, and the associated studies on degradation of dyes and phenols render these materials suitable for photocatalysis.     

A Giese reaction for electron-rich alkenes

A general method for the hydroalkylation of electron-rich terminal and non-terminal alkenes such as enol esters, alkenyl sulfides, enol ethers, silyl enol ethers, enamides and enecarbamates has been developed. The reactions are carried out at room temperature under air initiation in the presence of triethylborane acting as a chain transfer reagent and 4-tert-butylcatechol (TBC) as a source of hydrogen atom. The efficacy of the reaction is best explained by very favorable polar effects supporting the chain process and minimizing undesired polar reactions. The stereoselective hydroalkylation of chiral N-(alk-1-en-1-yl)oxazolidin-2-ones takes place with good to excellent diastereocontrol.

Giese reaction not anymore limited to electron poor alkenes! A general method for the radical mediated hydroalkylation of electron rich alkenes including enol ethers, silylenolethers, enamides, and enecarbamates has been developed.     

Synthesis and characterisation of small ZnS particles

Small ZnS particles, prepared at room temperature in an alcoholic medium using a zinc salt and thioacetamide as sulphur source, have been characterised using a suite of techniques which includes XRD, TEM and Zn K-edge EXAFS. The investigation suggests that aggregates of small sphalerite particles (cubic lattice), with average size of 3.5 nm and well-defined morphology are obtained and the particle size appears not to change with increase in the reaction time from 2 to 24 h. Zn K-edge EXAFS experiments were performed at 10 K, in order to reduce thermal disorder and the refinement of the EXAFS data resulted in very small second shell coordination numbers with respect to the bulk samples. The result is in good agreement with SEM and XRD data about the presence of nanosized particles, having a large number of surface atoms with low second shell coordination number.     

Neutron activation analysis of 13 minor and trace elements in geological samples

A scheme of analysis for the determination of Na, Mn, U, Th, Hf, Sc, La, Ce, Eu, Tb, Co, Rb and Cs in geological samples using the neutron activation technique has been described. The results obtained in this work on eight geological standard rocks and a trachyte are presented and compared with literature data.     

Kinetics of oxidation of sulphite by hexachloroplatinate(IV) in acidic solution

Summary The kinetics of the oxidation of sulphite by hexachloroplatinate(IV) has been studied over wide range of experimental conditions. The reaction is first-order in substrate and in platinum(IV). The rate decreases with the increase in acidity. The effect of salt and of changing dielectric constants on the reaction rate have been studied. Values of H and S have been calculated and are 26.3 kJ mol^–1 and –35.9 JK^–1 mol^–1, respectively. On the basis of experimental evidence, a two-electron reduction mechanism is proposed.     

A simple method of isolation of chloramphenicol in honey and its estimation by liquid chromatography coupled to electrospray ionization tandem mass spectrometry

To detect sub-ppb levels of the antibiotic chloramphenicol in honey matrix, a convenient method of extraction and measurement using liquid chromatography with detection by tandem mass spectrometry (LC/MS/MS) was developed. Honey samples fortified with chloramphenicol and isotopically labeled chloramphenicol were extracted using diatomaceous-based supported liquid-liquid extraction cartridges to generate a standard calibration curve. Four MS/MS transitions were used for quantification and four other transitions for confirmation of chloramphenicol. The limit of detection for chloramphenicol was 0.05 ng/g and the lower limit of quantification was 0.1 ng/g. Several commercial honey samples were analyzed for chloramphenicol content using this method.     

Simplifying the complex 1H NMR spectra of fluorine-substituted benzamides by spin system filtering and spin-state selection: multiple-quantum-single-quantum correlation

The proton NMR spectra of fluorine-substituted benzamides are very complex (Figure 1) due to severe overlap of (1)H resonances from the two aromatic rings, in addition to several short and long-range scalar couplings experienced by each proton. With no detectable scalar couplings between the inter-ring spins, the (1)H NMR spectra can be construed as an overlap of spectra from two independent phenyl rings. In the present study we demonstrate that it is possible to separate the individual spectrum for each aromatic ring by spin system filtering employing the multiple-quantum-single-quantum correlation methodology. Furthermore, the two spin states of fluorine are utilized to simplify the spectrum corresponding to each phenyl ring by the spin-state selection. The demonstrated technique reduces spectral complexity by a factor of 4, in addition to permitting the determination of long-range couplings of less than 0.2 Hz and the relative signs of heteronuclear couplings. The technique also aids the judicious choice of the spin-selective double-quantum-single-quantum J-resolved experiment to determine the long-range homonuclear couplings of smaller magnitudes.     

Allylations of chelated enolates using dienyl substrates

Isomerization-free reactions of dienyl carbonates (1-3) with chelated amino acid ester enolates at -78 degrees C provide important information concerning the mechanism of these dienylations. The formation of regioisomeric products can be explained by competing SN2/SN2' reactions, and the product distribution can be influenced by proper choice of the reaction conditions.     

Metalation of 2HTCNPP on Ag(111) with Zn: Evidence for the Sitting atop Complex at Room Temperature

We study the interaction and metalation reaction of a free base 5,10,15,20-terakis(4-cyanophenyl)porphyrin (2HTCNPP) with post-deposited Zn atoms and the targeted reaction product Zn-5,10,15,20-terakis(4-cyanophenyl)porphyrin (ZnTCNPP) on a Ag(111) surface. The investigations are performed with scanning tunneling microscopy at room temperature after Zn deposition and subsequent heating. The goal is to obtain further insights in the metalation reaction and the influence of the cyanogroups on this reaction. The interaction of 2HTCNPP with post-deposited Zn leads to the formation of three different 2D ordered island types that coexist on the surface. All contain a new species with a bright appearance, which increases with the amount of post-deposited Zn. We attribute this to metastable SAT (“sitting atop”) complexes formed by Zn and the macrocycle, that is, an intermediate in the metalation reaction to ZnTCNPP, which occurs upon heating to 500 K. Interestingly, the activation barrier for the successive reaction of the SAT complex to the metalated ZnTCNPP species can also be overcome by a voltage pulse applied to the STM tip.