Telluride Misfit Layer Compounds: [(PbTe)1.17]m(TiTe2)n

Telluride misfit layer compounds are reported for the first time. These compounds were synthesized using a novel approach of structurally designing a precursor that would form the desired product upon low‐temperature annealing, which allows the synthesis of kinetically stable products that do not appear on the equilibrium phase diagram. Four new compounds of the [(PbTe)_1.17]_m(TiTe₂)_n family are reported, and their structures were examined by a variety of X‐ray diffraction techniques.     

Cationic radius ratio and formation of K2NiF4-type compounds

A survey of known compounds which can assume K₂NiF₄-type structure at least over a certain P, T range was made. The cationic radius ratios r_A/r_B of this family of compounds were found to vary over a relatively narrow range of values around 2.00, in contrast to the much wider ranges known for other important A₂BX₄ structure groups, e.g., β-K₂SO₄, thenardite, olivine, etc., providing thereby a constraint on the crystal chemical variabilities in this group of compounds. Usefulness of the simple size parameter r_A(IX)/r_B(VI) in predicting formation of new K₂NiF₄-type compounds is discussed.     

新型三硅氧烷表面活性剂的合成与界面性能

低聚乙二醇单甲醚和环氧氯丙烷在相转移催化剂(P.T.C)存在下合成出低聚乙二醇甲醚缩水甘油醚, 然后与氨丙基三硅氧烷进行开环反应, 合成出了新型的三硅氧烷表面活性剂Me₃SiOSiMeROSiMe₃ [R＝(CH₂)₃N(CH₂CH(OH)CH₂- (OCH₂CH₂)_xOCH₃)₂, x＝1, 2]. 通过¹H NMR确证了这些目标产物的结构, 并且通过测定其水溶液的平衡表面张力研究了其表面活性. 在浓度约为10^－4 mol•L^－1时可以将水的表面张力降低至约21～22 mN•m^－1.     

A new structural type of liquid crystal Crystal structures and thermotropic mesophases of dihydroxytetraalkyldisiloxanes: Columnar phases with hydrogen bonded assemblies

Abstract

Previous structural investigations of mesogenic organosilicon compounds (1, 3-dihydroxytetraalkyldisiloxanes, [R₂(OH)Si]₂O, R = C _n H_2n+1) which form thermotropic phases are outlined. The crystal and molecular structure determination of a non-mesogenic member of this series [Me₂(OH)Si]₂O is described. It is inferred that the mesophases formed by this family of compounds belong to a new structural type with columnar stacks of the molecules laced together with hydrogen bonds.     

Synthese Des 5-Desoxy-5,5,5-Trifluoro-d- et -l-Pentofuranoses

ABSTRACT

Synthetic pathways leading to 5-deoxy-5,5,5-trifluoropentofuranoses are reported. The main difficulty was to obtain a good diastereoselectivity at the C-4 carbon bearing the CF₃ group. For the ribose and the lyxose derivatives the problem was partially solved by reacting trifluoromethyltrimethylsilane with 1,4-lactones of suitable glyconic acids leading to hemiketalic 1-deoxy-1,1,1-trifluoro-2-ketoses. Reduction of these ketoses with NaBH₄ or LiA1H₄ allowed the desired configuration at the C-4 carbon. For the arabinose and the xylose derivatives it was found more convenient to synthesize uncyclised 1-deoxy-1,1,1-trifluoro-2-ketopentoses by Dess-Martin oxidation of the corresponding protected alcohols. Highly selective reductions of these trifluoromethylketones led to arabino or xylo derivatives depending on the reducing agent.     

Synthese et Comportement Polarographique Des Cis et Trans Azoxycyclohexanes

Abstract

In order to compare the polarographic behaviour of cis and trans aliphatic azoxy compounds, synthesis and polarographic study of cis and trans azoxycyclohexanes are performed. The cis form is a new compound obtained by photoisomerisation of the trans compound. In acid medium the polarographic reduction process is the same for both forms: hydrazocyclohexane is the final reduction product. In alkaline medium the trans azoxy compound is electroinactive and the cis azoxy compound is reducible and leads to a mixture of trans azocyclohexane and hydrazocyclohexane.     

Antiferromagnetic Ordering and Structural Characterization of the Brown Colored R2BaCoO5 Oxides (R = Rare Earth)

New R₂BaCoO₅ oxides (_R = rare earth) have been prepared in Ar flow, and the X-ray diffraction data reveal that they crystallize in the Nd₂BaNiO₅ structural type (space group Immm ). The existence of dimorphism has been shown for R = Dy, Ho, Er, and Tm. A comparative study of the influence of the rare earth size on the structural parameters is presented for this family of compounds. The relative stability of these oxides is discussed from the variation of the so-called global instability index (GII) calculated using the bond valence method. The GII values around 0.2 v.u. are indicative of the high stress present in this structure. The magnetic properties of these oxides have been studied from magnetic susceptibility measurements and one-dimensional antiferromagnetic correlations in the Co⁺² sublattice are presented around the room temperature, while three-dimensional antiferromagnetic interactions in both R⁺³ and Co⁺² sublattices have been observed at lower temperatures (T_Néel < 40 K) in this family of oxides. This behavior is explained considering the crystal structure of these compounds and the electronic states of the Co⁺² and R⁺³ cations.     

LiBaAlF6 and the crystal chemistry of LiAIIBIIIF6 phases

Lithium barium hexafluoroaluminate (LBAF), LiBaAlF₆, is a new member of the large family of compounds of formula LiA^IIB^IIIF₆. These materials display a variety of structures depending on the sizes of the A and B cations. LiBaAlF₆, which is isomorphous with LiBaCoF₆, belongs to the monoclinic P2₁/c subset and has a three‐dimensional network structure consisting of distorted LiF₄³⁻ tetrahedra corner‐sharing with AlF₆³⁻ octahedra and BaF₁₂ polyhedra. All of the atoms reside on general positions. An analysis of the ionic radii of the A cations versus formula volumes for the known members of the family yields a structure map that reasonably segregates the compounds by space group. The data obtained are thus suitable for predicting new isomorphic crystal structures.     

Mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones and their derivatives

The mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones (compounds 1) and their 2,4-dinitrophenylhydrazones (compounds 2) and semicarbazones (compounds 3) have been studied. The characteristic fragments at m/z (M ? 73) from compounds 1, m/z (M ? 253) from compounds 2 and m/z (M ? 130) from compounds 3 are abundant and proposed to be [ArCROCH₃]⁺. Fragmentations yielding [M⁺ ? 49] from compounds 2 are abnormal and probably involve the methoxyl and nitro groups. The intense peak at m/z 130 due to [CH₃OCH₂CNNHCONH₂]⁺ from compounds 3 corresponds to α-cleavage of the molecular ion. Some other fragments from these new compounds are interpreted in this paper.     

Preparation, structure, and properties of new ternary rhenium arsenides and phosphides with metal-metal bondings

The M₂Re₅As₁₂ arsenides (M = Fe, Co, Ni) and the Co₂Re₅P₁₂ phosphide were synthesized. The unit cell is orthorhombic with space group Pnnm and contains two formula units. The X-ray structure of Ni₂Re₅As₁₂ was studied from three-dimensional single-crystal counter data and was refined down to R = 0.048 for 637 independent reflections. The structure can be described as built up from two different structural domains; the first one is the marcasite type and shows As---As pairs and linear Re---Re chains, the second one consists of Re₄ clusters with common edges linked to terminal Ni atoms. A nearly temperature-independent paramagnetism and p-type metallic conduction were observed from the magnetic and electrical measurements. Also observed in this new family of compounds were the resistivities along and perpendicular to the c axis and their anisotropic behavior.     

Anionic Sublattices in Halide Solid Electrolytes: A Case Study with the High-Pressure Phase of Li3ScCl6

The Li₃MX₆ compounds (M=Sc, Y, In; X=Cl, Br) are known as promising ionic conductors due to their compatibility with typical metal oxide cathode materials. In this study, we have successfully synthesized γ-Li₃ScCl₆ using high pressure for the first time in this family. Structural analysis revealed that the high-pressure polymorph crystallizes in the polar and chiral space group P6₃mc with hexagonal close-packing (hcp) of anions, unlike the ambient-pressure α-Li₃ScCl₆ and its spinel analog with cubic closed packing (ccp) of anions. Investigation of the known Li₃MX₆ family further revealed that the cation/anion radius ratio, r_M/r_X, is the factor that determines which anion sublattice is formed and that in γ-Li₃ScCl₆, the difference in compressibility between Sc and Cl exceeds the ccp r_M/r_X threshold under pressure, enabling the ccp-to-hcp conversion. Electrochemical tests of γ-Li₃ScCl₆ demonstrate improved electrochemical reduction stability. These findings open up new avenues and design principles for lithium solid electrolytes, enabling routes for materials exploration and tuning electrochemical stability without compositional changes or the use of coatings.     

Cs6Nb4Se22 and K12Nb6Se35.3: two new compounds containing the M4Q22 building block

The title compounds, namely hexacaesium tetraniobium docosaselenide and dodecapotassium hexaniobium pentatriacontaselenide, were formed from their respective alkali chalcogenide reactive flux and niobium metal. Both compounds fall into the larger family of solid‐state compounds that contain the M₂Q₁₁ building block (M = Nb, Ta; Q = Se, S), where the metal chalcogenide forms dimers of face‐shared pentagonal bipyramids. Cs₆Nb₄Se₂₂ contains two Nb₂Se₁₁ building blocks linked by an Se—Se bond to form isolated Nb₄Se₂₂ tetrameric building blocks surrounded by caesium ions. K₁₂Nb₆Se_35.3 contains similar Nb₄Se₂₂ tetramers that are linked by an Se—Se—Se unit to an Nb₂Se₁₁ dimer to form one‐dimensional anionic chains surrounded by potassium ions. Further crystallographic studies of K₁₂Nb₆Se_35.3 demonstrate a new M₂Se₁₂ building block because of disorder between an Se²⁻ site (85%) and an (Se—Se)²⁻ unit (15%). The subtle differences between the structures are discussed.     

Molecular design of all nitrogen pentazole‐based high energy density compounds with oxygen balance equal to zero

We designed a new family of pentazole‐based high energy density compounds with oxygen balance equal to zero by introducing −NH₂, −NO₂, −N₃, −CF₂NF₂, and −C[NO₂]₃, and the properties including density, heats of formation, detonation performances, and impact sensitivity were investigated using density functional theory. The results show that half of these new energetic molecules exhibit higher densities than RDX (1.82 g/cm³), in which H5 gives the highest density of 2.09 g/cm³. Among all the 54 designed molecules, 22 compounds have higher D and P than RDX and eleven compounds have higher D and P than HMX, indicating that designing the pentazole‐based derivatives with oxygen balance equal to zero is a very effective way to obtain potential energetic compounds with outstanding detonation properties. Taking both the detonation performance and stability into consideration, nine compounds may be recognized as potential candidates of high energy density compounds. It is expected that our results will contribute to the theoretical design of new‐generation energetic explosives.     

Derivate des borabenzols: XVIII. Vanadium-komplexe Des 1-methyl- und 1-phenylborinat-ions

Six borabenzene derivatives of vanadium are described. Reaction of the alkali metal borinates M(C₅H₅BR) (M = Na, K; R = Me, Ph) with VCl₃ yields the paramagnetic, sandwich complexes V(C₅H₅BR)₂. Reaction with HgCl₂ and [Na{O(CH₂CH₂OCH₃)₂}₂][V(CO)₆] affords the tetracarbonyl compounds V(CO)₄(C₅H₅BR). Upon heating in cycloheptatriene, the latter compounds produce the paramagnetic cycloheptatrienyl complexes V(C₅H₅BR)(C₇H₇) with sandwich structures. An X-ray structural study of V(CO)₄(C₅H₅BMe) shows that the V(CO)₄ fragment in the crystal is rotated by 10.4° relative to an ideal, eclipsed conformation where two CO groups are present in the plane through the B, V and C(4) atoms.     

Synthesis and structural characterization of tricarbonyl bis-[Di(N,N′'-allylamino)carbene]chromium and tungsten(0) complexes

Summary The reaction in situ of [M(CO)₆] (M = Cr or W), 1,2-bis(N-allylamino)ethane and CH(NMe₂)(OMe)₂ has resulted in the isolation of chelated metal carbene compounds in low yield. A [3,3] amino-Claisen rearrangement of a transient allyl electron-rich olefin, the organic precursor of the carbenes, appears to be the principal product. A single crystal X-ray diffraction study has shown that the tungsten complex has similar structural parameters to a molybdenum-carbene previously communicated. Detailed characterization of family six (G, No, W) chelated carbene compounds has been completed.     

First report of antioxidant abeo-labdane type diterpenoid from intertidal red seaweed Gracilaria salicornia with 5-lipoxygenase inhibitory potential

Abstract

Phytochemical investigation on the biologically active compounds of seaweed Gracilaria salicornia {(C. Agardh) E.Y. Dawson} (family Gracilariaceae) guided to the separation of a previously unreported abeo-labdane class of diterpenoid. The compound was characterized as methyl-16(13→14)-abeo-7-labdene-(12-oxo) carboxylate by extensive spectroscopic experiments, and comparison with the related compounds. The studied compound registered significantly greater activities against pro-inflammatory 5-lipoxygenase (IC₅₀ 0.86?mg/mL) than that exhibited by non-steroidal anti-inflammatory agent ibuprofen (IC₅₀ 0.92?mg/mL, P?<?0.05). Likewise, this compound exhibited comparable radical quenching (1, 1-diphenyl-2-picryl-hydrazil) activity (IC₅₀ 0.66?mg/mL) as standard antioxidant agent α-tocopherol (IC₅₀ 0.62?mg/mL).     

Using the QSPR Approach for Estimating the Density of Azole‐based Energetic Compounds

The relationship between density of energetic azole‐based compounds and their molecular structure is investigated through quantitative structure‐property relationship (QSPR) approach. The methodology of this work introduces a new model, which related density of azole‐based energetic compounds to the optimum elemental composition, the degree of unsaturation (DoU) of the compounds, presence of nitroimino group in the structural formula, as well as several non‐additive structural parameters. The presence of nitroimino functional group and also increasing the value of n_O/n_N in the formula of these compounds can enhance their density. The correlation is derived on the basis of experimental density values of 100 azole‐based energetic compounds with different molecular structure as training set. The determination coefficient of the new correlation is 0.923. Also, it has the root mean square deviation (RMSD) and the average absolute deviation (AAD) of 0.038 and 0.030 g · cm^–3, respectively. In addition, the correlation gives good predictions for further 25 azole‐based energetic compounds as test set (Q²_EXT = 0.901). The predictive ability of the correlation is checked using a cross validation method (Q²_LMO = 0.918). The proposed method can also apply for designing novel azole‐based energetic compounds.     

“114”‐Type Nitrides LnAl(Si4−xAlx)N7Oδ with Unusual [AlN6] Octahedral Coordination

Aluminum–nitrogen six‐fold octahedral coordination, [AlN₆], is unusual and has only been seen in the high‐pressure rocksalt‐type aluminum nitride or some complex compounds. Herein we report novel nitrides LnAl(Si_4−x Al_x)N₇O_δ (Ln=La, Sm), the first inorganic compounds with [AlN₆] coordination prepared via non‐high‐pressure synthesis. Structure refinements of neutron powder diffraction and single‐crystal X‐ray diffraction data show that these compounds crystallize in the hexagonal Swedenborgite structure type with P 6₃mc symmetry where Ln and Al atoms locate in anticuboctahedral and octahedral interstitials, respectively, between the triangular and Kagomé layers of [SiN₄] tetrahedra. Solid‐state NMR data of high‐purity La‐114 powders confirm the unusual [AlN₆] coordination. These compounds are the first examples of the “33‐114” sub‐type in the “114” family. The additional site for over‐stoichiometric oxygen in the structure of 114‐type compounds was also identified.     

Reaktionen Gespannter C—C Einfachbindungen Mit Übergangsmetallen : XI. Eisencarbonylderivative Des Homosemibullvalen

The light-induced reaction of homosemibullvalene with Fe(CO)₅ under kinetic control gives iron carbonyl compounds resulting from exo-attack at the bicyclo[3.1.0]hexene unit and a bis-allyl complex from endo-attack at the divinylcyclopropane unit; an iron carbonyl complex derived from the bicyclo[4.1.0]heptene part has been obtained on thermodynamically-controlled reaction with Fe₂(CO)₉ in refluxing hexane.     

Mass spectrometry: XI—Electron impact induced fragmentation of some amides of F-acids and their deuterated homologues

The mass spectrometry of perfluoro compounds (F-alkyl compounds) has seldom been the subject of systematic studies. Fluorocarbons excepted, only a few mass spectra of such compounds have been analysed and corresponding fragmentations correlated. In this paper we report the mass spectra of 19 amides of perfluoro acids (R_FCONHR) with R=benzyl, 2-phenylethyl, 2-phenylpropyl, 3-phenylpropyl, 2-(N-phenylamino)ethyl, and R_F=F-methyl, n-perfluoropropyl, n-perfluoropentyl and n-perfluoroheptyl. These compounds exhibit quite different behaviour from their hydrocarbon homologues under electron impact (for instance no [R_FCO]⁺ fragment was found). Specific deuterium labelling and high resolution measurements have been used to show typical rearrangements and to establish the fragmentation routes.