Impact sensitivity of energy systems based on nanoporous silicon and oxidant: influence of the hydrogen content and specific surface

The impact sensitivity of the energy systems based on nanoporous silicon, obtained by electrochemical etching of monocrystalline silicon wafers in an HF-containing electrolyte, and calcium perchlorate was studied using a modified Weller—Ventselberg technique (estimation of the impact sensitivity of initiating explosives). The impact sensitivity of these systems is shown to be determined by both the presence of hydrogen, which is stored on the porous silicon surface during the preparation of the latter, and also the influence of other factors, including the specific surface of porous silicon. The composition, amount of the generated gas, and gas evolution rate during nonisothermal and isothermal calcination of porous silicon in a temperature range of 60—120 °С were determined using methods of thermal gravimetry (TG), measurement of the gas volume, and mass spectrometry. The generated gas almost completely consists of hydrogen, and its content in the studied samples of porous silicon achieved ~3.8 wt.%. The calculated activation energy of the hydrogen evolution process in vacuo was 103.7±3.3 kJ mol^–1. The dependences of the impact sensitivity of the energy composition based on porous silicon and heat of combustion of porous silicon on oxygen on the hydrogen content were established. The impact sensitivity of the energy system decreases with a decrease in the hydrogen content in porous silicon and its specific surface.     

1,4,7,10‐Tetra­oxacyclo­dodeca­ne–triphenyl­methane­thiol (1/2)

In the centrosymmetric formula unit of the title complex, C₈H₁₆O₄·2C₁₈H₁₆S, the 1,4,7,10‐tetra­oxacyclo­dodecane mol­ecule adopts the biangular [66] conformation, and the triphenyl­methane­thiol mol­ecules are linked to the macrocycle via a long S—H⋯O hydrogen bond [S⋯O = 3.460 (2) Å and S—H⋯O = 161 (2)°]. Attractive inter­actions of phenyl groups in edge‐to‐face conformations combine inversion‐related formula units into chains running along the [111] direction in the crystal structure. Association of the chains into sheets is achieved via C—H⋯π inter­actions.     

Intermolecular overlap geometry gives two classes of fulleride superconductor: electronic structure of 38 K Tc Cs3C60

Superconductivity emerges for the A15 polymorph of the fulleride Cs3C60 upon compression to a pressure of approximately 4 kbar. Using density functional theory we study the bonding in the A15 phase as a function of unit cell volume comparing it to that in the fcc polymorph. We find that, despite its smaller packing density, the bcc-derived A15 phase has both a substantially wider bandwidth for the partially occupied t1u band and a higher density of states at the Fermi level. This result can be traced to the striking differences in the nature of the interanion Tc--the two sphere packings (body centered versus face centered) observed experimentally produce two electronically distinct classes of fulleride superconductors.     

NMR Spectra of Guest–Host Complexes of Boron and Silicon Fluorides with Crown Ethers in Nonaqueous Solutions

¹⁹F, ¹¹B, and ²⁹Si NMR spectroscopy was used to examine the behavior of the guest–host complexes (BF₃· H₂O)₂· 18-crown-6 · 2H₂O, (BF₃· H₂O)₂· DCH-6B, and (DCH-6A · H₃O)SiF₅in acetone (DCH-6B and DCH-6A are the cis-anti-cis- and cis-syn-cis-isomers of dicyclohexano-18-crown-6, respectively). It was shown that molecular boron fluoride complexes undergo partial solvolysis in acetone to yield BF₃· acetone as the main product; the ionic pentafluorosilicate complex does not experience significant solvolysis transformations.     

Crystal structures of molecular complexes of 18-crown-6 with 2-aminobenzoic and 5-amino-1-benzyl-1,2,3-triazole-4-carboxylic acid hydrazides

The crystal structures of two host-guest molecular complexes of 18-crown-6 with 2-aminobenzoic acid hydrazide monohydrate (the ratio host: guest: H₂O = 1: 2: 2) (complex I) and 5-amino-1-benzyl-1,2,3-triazole-4-carboxylic acid hydrazide (the host: guest ratio = 1: 2) (complex II) are determined by X-ray diffraction analysis. Crystals I are monoclinic, a = 8.468(2) Å, b = 17.378(3) Å, c = 10.517(2) Å, β = 96.88(3)°, space group P2₁/n, and R = 0.0393 for 6692 reflections. Crystals II are orthorhombic, a = 18.489(1) Å, b = 10.192(3) Å, c = 20.412(2) Å, space group Pbca, and R = 0.0540 for 3513 reflections. In both complexes, the centrosymmetric 18-crown-6 and guest molecules are joined together through the NH?O (crown) hydrogen bonds, which involve all the hydrogen atoms of the hydrazine group. The NH?O=C intramolecular hydrogen bond is observed in the guest molecule. In structure I, the water molecule serves as a bridge between the guest molecules related by the glide-reflection plane and combines the guest-host-guest complexes into layers. In structure II, the guest molecules are linked into chains through hydrogen bonds of the NH?O=C type; in turn, the chains composed of guest molecules and the crown ether molecules bonded to these chains form a layered structure.     

Stabilization of germanium(IV) aquafluorocompounds in host-guest type complexes with crown ethers. synthesis,crystal structure and ir spectra of the complexes [(GeF5-H2O)2-(H2-1,10-Diaza-l 8-Crown-6)] and [(trans-GeF4 · 2H2O) · 18-Crown-6·2H2O]

Stable products have been obtained from the interaction of GeO₂-HF solution with 18-membered crown ethers, 1,10-diaza-l8-crown-6 and 18-crown 6. Complexes were characterized by X-ray analysis and IR spectroscopy. Both Ge(IV) aquafluorocompounds are isostructural with their Si analogues. It was established that in the host-guest type complexes the germanium moiety as a central atom has been stabilized in the form of octahedral complexes. The host-guest interaction occurs by means of O-H(W)...O_cr, OH...F and N-H...F hydrogen bonds.     

Twelve-membered crown ethers: Crystal structures of benzo-12-crown-4 and naphtho-12-crown-4

The crystal structures of two 12-membered crown ethers, benzo-12-crown-4 (1) and naphtho-12-crown-4 (2), have been determined by X-ray analysis. Both structures are molecular. Compound1 is monoclonic,P2₁/b,a=8.466(3),b=8.019(3),c=33.590(10) Å, =90.99(3)^o. The unit cell contains two crystallographically independent molecules of1 with similar conformations. Compound2 is also monoclinic,P2₁/a,a=24.148(8),b=14.535(4),c=7.987(5) Å, =102.87(2)^o. Two independent molecules in the unit cell have significantly different conformations. Supplementary data relating to this publication have been deposited with the British Library as Supplementary Publication No. SUP 82145 (19 pages).     

Synthesis and structures of molecular complexes of the cis-anti-cis diastereomer of dicyclohexano-18-crown-6 with o-nitroanilines

In the reaction of the cis-syn-cis and cis-anti-cis diastereomers of dicyclohexano-18-crown-6 with 2-nitro and 2,4-dinitroaniline crystalline complexes with a 1:2 stoichiometric composition were obtained only when the cis-anti-cis diastereomer was used. The three-dimensional structure of the complex of the cis-anti-cis diastereomer of dicyclohexano-18-crown-6 with 2,4-dinitroaniline was determined by an x-ray diffraction study. The complexing of o-nitroanilines with the cis-anti-cis diastereomer is explained by the topological conformity of the interacting compounds. The isolation of the individual cis diastereomers from the mixture of them formed as a result of the catalytic hydrogenation of dibenzo-18-crown-6 was accomplished by means of the selective formation of the crystalline complex of the cis-anti-cis diastereomer with 2-nitroaniline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1190–1195, September, 1988.     

Interaction of N,N′-polyoxyethylenediphthalimides with diethylenetriamine and mass spectral behavior of the macrocyclic diamides of phthalic acid formed

The reaction of diethylenetriamine and diphthalimides containing a polyoxyethylene fragment yielded macrocyclic diamides of phthalic acid, and the fragmentation of these compounds under the action of electron impact was studied. It was established that their decomposition consists of an initial ejection of a C₂H₄N radical, presuming a rearrangement of the molecular ions to the corresponding N-substituted phthalimides, followed by the splitting out of ethylene oxide and water molecules in various orders. These mass spectral principles can be used to establish the number and sequence of monomer units in the macrocycles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1048–1051, August, 1984.