PROPIOLATE CLUSTER COMPLEXES (Bu4N)2[Mo6X8(OOC–C≡CH)6] (X = Br,I)

Journal of Structural Chemistry - Two new cluster complexes (Bu4N)2[Mo6X8(OOC–C≡CH)6] (1) (X = Br) and (2) (X = I) are synthesized by the reaction of...     

WS2/MoS2 Heterostructures through Thermal Treatment of MoS2 Layers Electrostatically Functionalized with W3S4 Molecular Clusters

The preparation of 2D stacked layers combining flakes of different nature gives rise to countless numbers of heterostructures where new band alignments, defined at the interfaces, control the electronic properties of the system. Among the large family of 2D/2D heterostructures, the one formed by the combination of the most common semiconducting transition metal dichalcogenides, WS₂/MoS₂, has awakened great interest owing to its photovoltaic and photoelectrochemical properties. Solution as well as dry physical methods have been developed to optimize the synthesis of these heterostructures. Here, a suspension of negatively charged MoS₂ flakes is mixed with a methanolic solution of a cationic W₃S₄-core cluster, giving rise to a homogeneous distribution of the clusters over the layers. In a second step, a calcination of this molecular/2D heterostructure under N₂ leads to the formation of clean WS₂/MoS₂ heterostructures, where the photoluminescence of both counterparts is quenched, proving an efficient interlayer coupling. Thus, this chemical method combines the advantages of a solution approach (simple, scalable, and low-cost) with the good quality interfaces reached by using more complicated traditional physical methods.     

Observation of Coherent Population Trapping in Ensembles of Diamond NV-Centers under Ground-State Level Anticrossing Conditions

Optics and Spectroscopy - The coherent population trapping effect in ensembles of diamond NV-centers under ground-state level anticrossing conditions was implemented with the application of a...     

A characterization of a minimax test in the problem of testing two composite hypotheses

We obtain a characterization of a minimax test in the problem of testing two composite hypotheses via a solution of a dual problem. In comparison to previous results, our characterization is valid under much weaker assumptions, which became possible, in particular, due to a modification of a dual problem.     

Thermodynamic characteristics of triphenylantimony diacrylate

The heat capacity of triphenylantimony diacrylate Ph₃Sb(O₂CCH=CH₂)₂ was studied in an adiabatic vacuum calorimeter at 6?C350 K and differential scanning calorimeter at 330?C450 K. Melting was revealed at these temperatures; the melting point was estimated at 428.4 ± 0.5 K. It was accompanied by the partial decomposition of the substance. The low-temperature (20 K ?? T ?? 50 K) heat capacity was treated using the Debye theory of the heat capacity of solids and its multifractal model. The type of the structure topology was determined. The standard thermodynamic functions C _p ^o (T), H ^o(T) ? H ^o(0), S ^o(T), and G ^o(T) ? H ^o(0) of the compound in the crystal state were calculated from the obtained experimental data in the range from T ?? 0 to 428 K. The standard entropy of the formation of the crystalline compound Ph₃Sb(O₂CCH=CH₂)₂ at T = 298.15 K was determined.     

Magnetic and magnetooptical properties of multilayer ferromagnet-semiconductor nanostructures

The magnetic and magnetooptical properties of spin-tunneling multilayer permalloy-silicon carbide nanoheterostructures deposited by rf sputtering have been studied. Magnetometric and magnetooptical methods are used to show that the magnetic-semiconducting nanostructures have a complex magnetic structure and to track the evolution of the magnetic properties of these structures as functions of the magnetizing field and the thickness and sequence order of ferromagnetic and semiconducting layers in them. The induction response and the field and orientation dependences of the transversal Kerr effect are found to have anomalies. The experimental results are interpreted under the assumption that there is exchange interaction between the ferromagnetic and semiconducting layers through a thin magnetically ordered transition layer formed inside the interface.     

Interaction of Tris(3-Hydroxymethyl)Phosphine with Cinnamic Acids

Abstract

Phosphonium zwitterions of the known type R₃P⁺CH(Ar)CH₂CO₂ ^? (II) are obtained as a racemic mixture in moderate yield via a 1:1 reaction of cinnamic acids (Ar = phenyl, or substituted phenyl) with [HO(CH₂)₃]₃P in acetone at room temperature under Ar. The products are characterized by elemental analysis, ³¹P{¹H}-, ¹H-, and ¹³C{¹H}-NMR spectroscopies, and mass spectrometry, although they contain a minor coproduct formed via neutralization of the positive and negative charges of II with the respective acid and phosphine reactants (see Experimental Section). In CD₃OD, the monodeuterated salts R₃P⁺CH(Ar)CH(D)CO₂ ^? are formed as a mixture of diastereomers with d.r. values of ～2 to 8, depending on substituent groups present in the organic acid; in these studies, 2-HO-cinnamic acid is the most reactive, and β-methylcinnamic acid is the least reactive.     

Mechanochemical reactions of molybdenum and tungsten chalcohalides with (Bu4N)2[Zn(Dmit)2]. Crystal structure of (Bu4N)2[Mo3Se5.88S1.12(Dmit)3] · 1.15CH2Cl2

The mechanochemical reactions of cluster chalcohalides M₃Q₇X₄ (M = Mo, W; Q = S, Se, Te; X = Br, I) with (Bu₄N)₂[Zn(Dmit)₂] (Dmit is 1,3-dithia-2-thionedithiolate, C₃S₅ ^2?) are studied. It is shown that the reaction of Mo₃Se₇Br₄ with (Bu₄N)₂[Zn(Dmit)₂] followed by crystallization from CH₂Cl₂ results in the formation of a new compound of the composition (Bu₄N)₂[Mo₃Se_5.88S_1.12(Dmit)₃] · 1.15CH₂Cl₂ (I) characterized by IR spectroscopy, electrospray mass spectrometry, and X-ray structure analysis. Under similar conditions, W₃Q₇Br₄ and Mo₃Te₇I₄ form binuclear complexes [M₂O₂Q₂(Dmit)₂]^2? identified by electrospray mass spectrometry. Various types of nonvalent contacts Q…Q are observed in the crystal structure of compound I.     

Use of electromagnetically induced transparency for measurement of superhyperfine splitting of the levels of rare-earth metals doped in optical crystals

The results of experimental and theoretical investigations of the electromagnetically induced transparency regime on the ⁴ I _9/2-⁴ G _5/2 transition in Nd³⁺ ions doped in LaF₃ are presented. The superhyperfine splitting of the upper and lower working levels has been determined on the basis of the results obtained. A theoretical model adequately describing the parameters of the resonances of electromagnetically induced transparency has been developed by analyzing the experimental data. Original Russian Text ? R.A. Akhmedzhanov, A.A. Bondartsev, L.A. Gushchin, N.A. Zharova, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 9, pp. 646–650.