Platinum chalcogenido MCM-41 analogues. High hexagonal order in mesostructured semiconductors based on Pt(2+) and [Ge(4)Q(10)](4-) (Q = S, Se) and [Sn(4)Se(10)](4-) adamantane clusters

Highly periodic hexagonal honeycombs of platinum-germanium chalcogenide and platinum-tin selenide frameworks were prepared by linking corresponding [Ge(4)Q(10)](4)(-) (Q = S, Se) and [Sn(4)Se(10)](4)(-) clusters with Pt(2+) ions. The non-oxidic honeycombs designated as C(n)PyPtGeQ and C(n)PyPtSnSe were templated by the lyotropic liquid-crystalline phase of alkylpyridinium surfactant [C(n)H(2)(n)(+1)NC(5)H(5)]Br (C(n)PyBr) with n= 12, 14, 16, 18, 20, and 22. Although the materials are amorphous at the microscale, they have crystalline mesoporosity with well-ordered and aligned surfactant-filled cylindrical pores. In addition to high mesoscopic order, the pore-pore separation is adjustable with the surfactant chain length (i.e., value of n). The quality of these materials, as judged by the degree of hexagonal order, rivals or exceeds that reported for the highest quality MCM-41 silicates. The materials have the lowest band gap reported so far for mesostructured chalcogenides solids, in the range 1.5 < E(g)< 2.3 eV. The C(n)PyPtGeS analogues show intense photoluminescence at 77 K when excited with light above the band gap.     

Stereoselective synthesis of optically active disilanes and selective functionalization by the cleavage of silicon-naphthyl bonds with bromine

Optically active disilanes with one chiral silicon center, (R)-1,2-dimethyl-1-(naphth-1-yl)-1,2,2-triphenyldisilane and (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane, were obtained by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with methyldiphenylsilyllithium or by the reaction of methyldiphenylchlorosilane with optically active (S)-methyl(naphth-1-yl)phenylsilyllithium and by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with dimethyl(4-methoxynaphth-1-yl)silyllithium. Under the optimized conditions, the reactions proceeded with almost complete inversion for the cholorosilanes and retention for the silyl anions. Optically active disilanes with two chiral centers, (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane and (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane, were obtained in high optical purity by the reactions of corresponding optically active halogenosilanes (Cl or F) with optically active silyllithiums. The silicon-silicon bond and the silicon-naphthyl bond of (R)-1,1,2-trimethyl-1,2-di(naphth-1-yl)-2-phenyldisilane and (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane were cleaved without selectivity on bromination. The silicon-(4-methoxynaphth-1-yl) bond of (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane was regiospecifically cleaved, followed by the stereoselective cleavage of the remaining chiral silicon-naphthyl bond (94% inversion). Although the silicon-(4-methoxynaphth-1-yl) bonds of (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane (> 99% ee) were regioselectively cleaved without silicon-silicon bond scission, remarkable racemization could not be avoided during the one-pot reaction.     

Results from the KGF proton decay experiment

Summary The data from the KGF experiment at the depth of 2.3 km underground are used to search for GUT signals in the form of nucleon decay oscillation and monopoles. Four events are considered as candidates for nucleon decay, whereas one plausible event is recorded to correspond to oscillation. Using different methods the monopole flux is shown to be <10⁻¹⁴ cm⁻² s⁻¹ sr⁻¹ for velocity range 10⁻³ c÷c. The angular distribution of cosmic-ray muons is used to derive an upper limit of 10⁻³ for the flux of prompt muons of energy up to a few hundred TeV in comparison to pions of same energy at production.

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Riassunto Si usano i dati dell'esperimento KGF alla profondità di 2.3 km sottoterra per ricercare segnali di GUT sotto forma di decadimento di nucleoni, oscillazioni e monopoli. Quattro eventi possono esser considerati come candidati per il decadimento di nucleoni, mentre si è registrato un evento che plausibilmente corrisponde all'oscillazione . Si mostra, con metodi diversi che il flusso di monopoli è <10⁻¹⁴ cm⁻¹ s⁻² sr⁻¹ nel-l'intervallo di velocità 10⁻³ c÷c. Si fa uso della distribuzione angolare dei muoni dei raggi cosmici per dedurre un limite superiore di 10⁻³ al flusso di muoni pronti di energia sino a qualche centinaio di TeV in rapporto ai pioni con la stessa energia di produzione.

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Резюме Данные, полученные в эксперименте Колар Голд Филдна глубине 2.3 км, анализируются с целью поиска эффектов, предсказываемых теориями Веяикого Обьединения: распада нуклона, осцилляций , магнитных монополей. 4 события могут рассматриваться как кандидаты на нуклонный распад, 1 событие-как кандидат на переход . С применением различных методов анализа показано, что поток монополей <10⁻¹⁴ см⁻² с⁻¹ стер⁻¹ для диапазона скоростей 10⁻³ с. Из углового распределения мюонов космических лучей получен верхний предел для потока мюонов непосредственной генерации с энергиями до нескольких сотен ТэВ. Этот поток не превышает 10⁻³ потока пионов с теми же начальными энергиями.

     

Synthesis and structural study of thiacyclophanes utilizing dibromides and methane dithiolate

The synthesis of a series of thiacyclophanes and optically active binaphthol-based chiral thiacyclophanes is reported with XRD structure. Two diastereomeric tetrathiacyclophanes are designed and synthesized. The two diastereomers are evidenced by crystal structure; the single-crystal X-ray studies reveal that one of the isomers possesses an inherent property of self-assembling into a vertical stack of tunnel-like structures.     

Core-shell like Cu<Subscript>2</Subscript>O nanocubes enfolded with Co(OH)<Subscript>2</Subscript> on reduced graphene oxide for the amperometric detection of caffeine

The authors report on the fabrication of Co(OH)₂-enfolded Cu₂O nanocubes on reduced graphene oxide (rGO), and the use of this material in an electrochemical caffeine sensor. The rGO/Cu₂O/Co(OH)₂ composite was characterized by X-ray powder diffraction pattern analysis, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. A rotating disc glassy carbon electrode covered with the nanocomposite displays enhanced electrocatalytic activity towards the electro-oxidation of caffeine. The peak oxidation potential is at 1.4  V (vs. Ag/AgCl) and hence is strongly shifted to the negative side when compared to other modified electrodes. The calibration plot is linear in the 0.83 to 1200 μM concentration range, with a 0.4 μM detection limit (at a signal-to-noise ratio of 3). The modified electrode is sensitive, selective and stable. It was successfully applied to the determination of caffeine in (spiked) caffeine-containing beverages and coffee powder and gave recoveries that ranged from 95.7 to 98.3 %.

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Graphical abstract Co(OH)₂ enfolded Cu₂O nanocubes on reduced graphene oxide (rGO) for the caffeine sensor

     

N‐Methyl‐N‐(1‐phenyl­sulfonyl­indol‐2‐ylmethyl)­aniline

In the title compound, 2‐[(methylphenylamino)methyl]‐1‐(phenylsulfonyl)indole, C₂₂H₂₀N₂O₂S, the indole system is not strictly planar and the dihedral angle between the fused rings is 2.7 (1)°. The angles around the S atom of the sulfonyl substituent deviate significantly from the ideal value for tetrahedral geometry. The pyramidalization at the indole N atom is very small. Of the two C—H?O interactions, one influences the orientation of indole with respect to the sulfonyl group and the other determines the orientation of the phenyl bound to sulfonyl. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 89.6 (1)° with the best plane of the indole. The molecular packing is stabilized by C—H?π and C—H?O hydrogen bonds.     

Photosynthetic hydrogen production

Among various technologies for hydrogen production, the use of oxygenic natural photosynthesis has a great potential as can use clean and cheap sources—water and solar energy. In oxygenic photosynthetic microorganisms electrons and protons produced from water and redirected by the photosynthetic electron-transport chain via ferredoxin to the hydrogen-producing enzymes hydrogenase or nitrogenase. By these enzymes, e^? and H⁺ recombine and form molecular hydrogen. Hydrogenase activity can be very high but is extremely sensitive to the photosynthetically evolved O₂ that leads to reduced and unstable H₂ production. However, presently, several approaches are developed to improve the energetic efficiency to generate H₂. This review examines the main available pathways to improve the photosynthetic H₂ production.