Construction and evaluation of a hermetically sealed accurate ion mobility instrument

Ion mobility spectrometry (IMS) is widely used to detect and identify chemical warfare agents, narcotics, and explosives in the field based on their reduced mobility (K ₀ ) values. Current detection windows for these analytes can only be as narrow as ±2% of the K ₀ values for the analyte being sought. These wide detection windows cause false positive alarms when an interferent with a similar reduced mobility falls within the detection window and triggers an alarm. This results in the loss of time and money as resources are diverted to verify the alarm. A high rate of false positive alarms is caused by a discrepancy in the reported K ₀ values across the literature that is, at best, ± 2% of the average available values. By accurately and precisely measuring the variables affecting an ion’s K ₀ value, an accurate K ₀ value can be produced and the detection windows widths that are established using these reference values can be reduced. Components for accurate analyses have been assembled in the past and here the construction of an accurate ion mobility spectrometry drift tube is described that is accurate to 0.1% of the calculated K ₀ value and can be hermetically sealed without inserting the drift tube into a large vacuum chamber. Having a pressure sealed accurate ion mobility spectrometer will allow for the control of the pressure variable within the K ₀ equation and the safe analysis of hazardous chemicals. Here the construction of an inexpensive and easily reparable sealed drift tube is described.     

Crystal structure of KPb<Subscript>2</Subscript>Cl<Subscript>5</Subscript> and KPb<Subscript>2</Subscript>Br<Subscript>5</Subscript>

The KPb₂Cl₅ and KPb₂Br₅ crystals are monoclinic (P2₁/c) with a microtwinned structure. X-ray analysis of chloride resulted in the parameters a = 8.854(2) Å, b = 7.927(2) Å, c = 12.485(3) Å; β = 90.05(3)°, d_calc = 4.78(1) g/cm³ (STOE STADI4, MoK_α, 2θ_max = 80°), R₁ = 0.0702 for 4094 F ≥ 4 σ(F) reflections. For bromide, a = 9.256(2) Å, b = 8.365(2) Å, c = 13.025(3) Å; β = 90.00(3)°, d_calc = 5.62(1) g/cm³ (Bruker P4, MoK_α, 2θ_max = 70°), R₁ = 0.0692 for 3076 F ≥ 4 (F) reflections.     

Calculation of the concentration limits of detonation for liquid homogeneous explosive systems

The results of the crush method applied to the experimental determination of the concentration limit of detonation for binary systems based on tetranitromethane and fluoronitromethane are generalized. A universal line (for the class of standard explosives with the atomic composition C _a H _b N _c O _d F _e ) dividing the plane of pairs of dimensionless parameters (heat of explosion, coefficient of oxidizer excess) into regions of detonating solutions and those unable of detonation was found.     

Characterization and crystal structure of a new layered cadmium diphosphate: KCdHP<Subscript>2</Subscript>O<Subscript>7</Subscript>∙2H<Subscript>2</Subscript>O

A new potassium cadmium hydrogen diphosphate dihydrate, KCdHP₂O₇?2H₂O (1), has been synthesized by slow evaporation at room temperature and characterized by FT-IR, Raman, TG-DTA, and single crystal X-ray diffraction. Compound (1) crystallizes in the orthorhombic Pcmn space group with the unit cell parameters a = 6.5814(8) Å, b = 7.9428(9) Å, c = 15.961(6) Å, V = 834.4(3) Å3 and Z = 4. Its structure consists of polyhedral layers parallel to the ab plane where each CdO₆ octahedron (m position) shares four edges with three different diphosphate groups. In the Cd octahedron, two oxygen atoms residing in (m) special positions belong to coordinated water molecules. These layers are joint by K⁺ cations (4c Wyckoff position) and hydrogen bonds, leading thus to a two-dimensional framework. The structural model is supported by the bond-valence-sum validation tool as calculated valences are close to the formal oxidation numbers.     

Crystal and molecular structure of <Emphasis Type="Italic">tris</Emphasis>(<Emphasis Type="Italic">m</Emphasis>-chlorophenyl)phosphine selenide

The crystal and molecular structure of tris(m-chlorophenyl)phosphine selenide, C₁₈H₁₂Cl₃PSe (I), was investigated by X-ray diffraction (XRD) analysis. The trigonal rhombohedral structure of I (space group \(R\overline 3 c\), a = 14.110(2) Å, c = 32.360(4) Å, Z = 12) was solved by direct methods and refined by least squares in an anisotropic approximation (R = 0.029) for 1319 averaged measured reflections (CAD-4 automatic diffractometer, λCuK_α).     

Calculation of the composition of detonation products and optimization of dynamic characteristics for mixed explosives

A mathematical model describing the composition of products and dynamic characteristics for the detonation of a multicomponent mixture of condensed explosives was proposed. The model consists of a system of equations with respect to a possible composition and temperature with allowance for the laws of conservation, partial conditions of detailed equilibrium, and semiempirical functional dependence of the energy-release coefficient. The numerical solution of these equations makes it possible to predict a relative impulse, rate, and pressure of detonation of individual explosives and their mixtures and to solve the problem of optimization of the detonation characteristics by composition. The application of the model for the calculation of optimum compositions for standard explosives with the empirical formula C _a H _b N _c O _d F _e was considered.     

Synthesis and structure investigation of Co(III) complex salts with the perrhenate anion

Complex salts of the composition [Co(NH₃)₆](ReO₄)₃·2H₂O (I), [Co(en)₃](ReO₄)₃ (II), [Co(NH₃)₅H₂O](ReO₄)₃·2H₂O (III), and [Co(NH₃)₅Cl](ReO₄)₂·0.5H₂O (IV) are obtained. Their crystal structures are determined by single crystal XRD. Crystallographic characteristics: (I) a = 9.9797(3) Å, b = 12.6994(3) Å, c = 14.7415(4) Å, β = 102.870(1)°, C2/c space group; (II) a = 8.0615(3) Å, b = 8.4483(4) Å c = 8.8267(4) Å, α = 61.923(2)°, β = 89.552(2)°, γ = 72.295(2)°, P1 space group; (III) a = 8.0086(4) Å, b = 12.9839(6) Å, c = 17.5122(7) Å, β=91.858(1)°, P2₁/n space group; (IV) a = 14.9446(3) Å, b = 14.6562(4) Å, c = 12.2434(4) Å, Cmc2₁ space group.     

Hexa(isothiocyanato)chromates(III) of Some Yttrium Group Lanthanide(III) and Europium Complexes with Nicotinic Acid: Synthesis and Crystal Structures

Double ionic complexes [M(C₅H₅NCOO)₃(H₂O)₂][Cr(NCS)₆] · nH₂O, where M = Eu (I), n = 1.15; Dy (II), Er (III), n = 1.5; M = Yb (IV), n = 2, have been synthesized by the reaction between M(NO₃)₃, M = Eu, Dy, Er, Yb, K₃[Cr(NCS)₆], and nicotinic acid (C₅H₅NCOO) in an aqueous solution and studied by chemical analysis, IR spectroscopy, and X-ray diffraction. Crystals of complexes I–IV are monoclinic, space group P2₁/n, Z = 4; a = 9.5358(2) Å, b = 25.4871(5) Å, c = 15.4303(4) Å, β = 105.513(1)°, V = 3613.6(1) ų, ρ_calcd = 1.799 g/cm³ for I, a = 9.5901(5) Å, b = 25.8599(15) Å, c = 15.6316(9) Å, β = 106.829(2)°, V = 3710.6(4) ų, ρ_calcd = 1.782 g/cm³ for II, a = 9.5640(3) Å, b = 25.8936(11) Å, c = 15.6498(7) Å, β = 106.895(2)°, V = 3708.3(3) ų, ρ_calcd = 1.791 g/cm³ for III, and a = 9.5049(2) Å, b = 25.6378(4) Å, c = 15.5120(3) Å, β = 106.934(1)°, V = 3616.1(1) ų, ρ_calcd = 1.864 g/cm³ for IV.     

Solute–solvent interactions in 2,4-dihydroxyacetophenone isonicotinoylhydrazone solutions in N,N-dimethylformamide and dimethyl sulfoxide at 298–313 K on ultrasonic and viscometric data

The speed of sound (u), density (ρ), and viscosity (η) of 2,4-dihydroxyacetophenone isonicotinoylhydrazone (DHAIH) have been measured in N,N-dimethyl formamide and dimethyl sulfoxide at equidistance temperatures 298.15, 303.15, 308.15, and 313.15 K. These data were used to calculate some important ultrasonic and thermodynamic parameters such as apparent molar volume (V _{? s} ^st ), apparent molar compressibility (K _?), partial molar volume (V _? ⁰ ) and partial molar compressibility (K _? ⁰ ), were estimated by using the values of (V _? ⁰ ) and (K _?), at infinite dilution. Partial molar expansion at infinite dilution, (? _E ⁰ ) has also been calculated from temperature dependence of partial molar volume V _? ⁰ . The viscosity data have been analyzed using the Jones–Dole equation, and the viscosity, B coefficients are calculated. The activation free energy has been calculated from B coefficients and partial molar volume data. The results have been discussed in the term of solute–solvent interaction occurring in solutions and it was found that DHAIH acts as a structure maker in present systems.     

New complex of Zn(II) with 3,4,5-trimethoxybenzoate and 2-methylimidazolyl: Synthesis,structure, and luminescence properties

A new zinc(II) complex Zn(TMB)₂(2-MIM)(H₂O)₂ (I), where HTMB is 3,4,5-trimethoxybenzoic acid, 2-MIM is 2-methylimidazole, was synthesized and characterized by Powder X-ray diffraction, FT-IR and photoluminescence spectrum. The complex crystallizes in the monoclinic crystal system (space group C2/c) with the unit cell parameters: a = 18.104(9), b = 8.509(4), c = 17.688(9) Å, β = 103.185(9)°, Z = 4, R ₁ = 0.0740 and wR ₂ = 0.1790. At room temperature the photoluminescence spectrum of complex I in the solid state exhibits maximum excitation at 314 nm and maximum emission at 337 nm.     

Nickel(II) complexes of new polydentate carboxyamide: spectroscopic,kinetics of thermal decomposition and X-ray powder diffraction studies

Complexes of Ni^II with new ligands N′,N′′-bis(3-carboxy-1-oxoprop-2-enyl), 2-Amino-N-arylbenzamidine (C₂₁H₁₇N₃O₆), N′,N′′-bis(3-carboxy-1-oxopropanyl) 2-Amino-N-arylbenzamidine (C₂₁H₂₁N₃O₆) and N′,N′′-bis(3-carboxy-1- oxophenelenyl) 2-Amino-N-arylbenzamidine (C₂₉H₂₁N₃O₆) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, TOF-mass spectra, magnetic susceptibility measurements, thermal studies and X-ray powder diffraction studies. Vibrational spectra indicate coordination of amide and carboxylate oxygen of the ligands along with two water molecules giving a MO₆ weak field octahedral chromophore. Electronic spectra and magnetic susceptibility measurements reveal octahedral geometry for Ni^II complexes. The elemental analyses and mass spectral data have justified the ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The crystal data: C₂₁H₁₉N₃O₈ Ni is orthorhombic, space group P_mmm, a = b = 9.015360(Å), c = 10.554430(Å), V = 572.11A³; C₂₁H₂₃N₃O₈Ni is monoclinic, space group P_2/m, a = 15.08206(Å), b = 5.358276(Å), c = 9.898351(Å), V = 671.58A³; C₂₉H₂₃N₃O₈Ni is tetragonal, space group P_4/m, a = b = 6.328104(Å), c = 9.82213(Å), V = 393.33A³. Molecular structures of the complexes have been optimized by MM2 calculations and supported octahedral arrangements around Nickel(II) ions.     

Synthesis and crystal structure of ternary molybdate compound K<Subscript>5</Subscript>Pb<Subscript>0.5</Subscript>Hf<Subscript>1.5</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>6</Subscript>

Single crystals of triple molybdate of composition 5:1:3 K₅Pb_0.5Hf_1.5(MoO₄)₆ have been grown and their crystal structure has been solved from X-ray diffraction data (an automated diffractometer X8 APEX, MoK _α -radiation, 2173 F(hkl), R = 0.0321). Trigonal unit cell parameters are: a = b = 10.739(2) Å, c = 37.933(9) Å; V = 3789(1) ų, Z = 6, ρ_calc = 4.014 g/cm³, space group \(R\bar 3\). Three-dimensional mixed framework of the structure is formed by two types of MoO₄ tetrahedra and Pb and Hf octahedra linking via common O-vertices. Potassium atoms of three types occupy large vacancies in the framework.     

Synthesis,crystal structure,and kinetics of thermal decomposition of the Zn(II) complex with vanillin

A complex [Zn(C₈H₇O₃)₂(H₂O)₂] (C₈H₈O₃ is vanillin) has been synthesized and characterized by IR, elemental analysis, and X-ray diffraction single-crystal analysis. The crystals are monoclinic, space group C2/c, a = 22.236(8) Å, b = 10.594(2) Å, c = 7.8190(16) Å, α = 89.90(3)°, β = 106.87(4)°, γ = 89.99(3)°, V = 1762.6(8) ų, Z = 4, F(000) = 832, S = 1.079, ρ _c = 1.521g cm^?3, R = 0.0221, R _w = 0.0604, μ = 1.433 mm^?1. The Zn²⁺ ion is six-coordinated with a distorted octahedron geometry. The complex forms a three-dimensional network through intermolecular hydrogen bonds. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal conditions by the TG and DTG methods. The kinetic equation can be expressed as dα/dt = Ae^?E/RT 2(1 ? α)[1 ? ln(1 ? α)]^1/2. The kinetic parameters (E, A), activation entropy ΔS ^≠, and activation free-energy ΔG ^≠ were also gained.     

Synthesis and crystal structure of dimethylgold(III) carboxylates

Three novel carboxylate complexes were synthesized: dimethylgold(III) trifluoroacetate [Me₂Au(Tfa)]₂ (I), trimethylacetate (pivalate) [Me₂Au(Piv)]₂ (II), and benzoate [Me₂Au(OBz)]₂ (III). The starting reagent was [Me₂AuI]₂. The procedure of its synthesis provides 60% product yield. Dimethylgold(III) carboxylates were identified from the IR and ¹H NMR data. The title compounds were studied by X-ray diffraction. The unit cell parameters for I, C₈H₁₂Au₂F₆O₄: a = 15.5522(13), b = 12.9398(11), c = 15.6555(14) Å, β = 104.308(2)°, Z = 8, ρ(calcd.) = 2.959 g/cm³, space group C2/c, R = 0.0779; for II, C₁₄H₃₀Au₂O₄: a = 10.3025(3), b = 15.5952(4), c = 12.6819(3) Å, β = 105.8270(10)°, Z = 4, ρ(calcd.) = 2.224 g/cm³, space group P2₁/c, R = 0.0229; for III, C₁₈H₂₂Au₂O₄: a = 12.8050(2), b = 19.7886(3), c = 7.60300(10) Å, Z = 4, ρ(calcd.) = 2.401 g/cm³, space group Pnma, R = 0.0144. Compounds I–III have the molecular structures; the structural units are the [(CH₃)₂Au(OOCR)]₂ dimers (Au…Au 2.984–3.080 Å), R = CF₃, tert-Bu, Ph. The gold atoms have the square coordination with two carbon atoms and two oxygen atoms (Au-O 2.120–2.173 Å). The molecules in compounds I–III are united into infinite unidimensional chains connected by van der Waals interactions.     

Crystal and molecular structure of <Emphasis Type="Italic">E</Emphasis>-3-(1,3-dimethylindol-2-yl)methylene-4-isopropylidenetetrahydrofuran-2,5-dione

The crystal and molecular structure of E-3-(1,3-dimethylindol-2-yl)methylene-4-isopropylidenetetrahydrofuran-2,5-dione, C₁₈H₁₇NO₃ (I), was investigated by XRD. The monoclinic structure of I (space group P2₁/c, a = 12.411(2) Å, b = 7.586(1) Å, c = 16.107(3) Å, β = 96.90(2)°, Z = 4) was solved by direct methods and refined by the full-matrix least squares in an anisotropic approximation to R = 0.044 for all 2842 independent reflections collected (CAD-4 automatic diffractometer, λCuK _α). The geometric parameters of sterically strained molecule I were determined with a high accuracy.     

Molecular orientation ordering in surface layers of polymer films

The spontaneous ordering of fragments of chain molecules near the surface in polymer films is described in terms of the multichain model that allows for local intra-and interchain orientational interactions of chain segments and for transverse fluctuation of their orientation in the approximation of strong planar-orientation order in the layers. Chain packing in the plane-ordered state is impossible unless the interchain interaction parameter has a value of b = 2K ₂/k _B T > b _c. The value of b _c decreases with a growth in chain rigidity (parameter a = 2K ₁/k _B T). The calculated dependence of the limiting values of the quadrupole orientation order parameter S ₀ on the length of the Kuhn statistical segment A = 2a reasonably well describes the experimental data obtained in a study of polymer-homolog (polysaccharide) films by means of the tilted polarized-beam technique at an interchain interaction parameter of b = 1.75. The monolayer thickness (d ? 10 mn) is films of some polysaccharides was calculated from the fit of the theoretical to the experimental dependences of the orientational order parameter and the birefringence on the number of layers.     

Crystal structures of a family of layered coordination polymers containing divalent metal ions (Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) and the 3-amino 4-methyl benzoate ion

The syntheses and crystal structures of the layered coordination polymers M(C₈H₈NO₂)₂ [M = Mn (1), Co (2), Ni (3) and Zn (4)] are described. These isostructural compounds contain centrosymmetric trans-MN₂O₄ octahedra as parts of infinite sheets; the ligand bonds to three adjacent metal ions in μ³-N,O,O′ mode from both its carboxylate O atoms and its amine N atom. In each case, weak intra-sheet N–H?O and C–H?O hydrogen bonds may help to consolidate the structure. Crystal data: 1, C₁₆H₁₆MnN₂O₄, M _r = 355.25, monoclinic, P2₁/c (No. 14), a = 10.6534(2) Å, b = 4.3990(1) Å, c = 15.5733(5) Å, β = 95.1827(10)°, V = 726.85(3) ų, Z = 2, R(F) = 0.026, wR(F ²) = 0.067. 2, C₁₆H₁₆CoN₂O₄, M _r = 359.24, monoclinic, P2₁/c (No. 14), a = 10.6131(10) Å, b = 4.3374(4) Å, c = 15.3556(17) Å, β = 95.473(4)°, V = 703.65(12) ų, Z = 2, R(F) = 0.041, wR(F ²) = 0.091. 3, C₁₆H₁₆N₂NiO₄, M _r = 359.02, monoclinic, P2₁/c (No. 14), a = 10.6374(4) Å, b = 4.2964(2) Å, c = 15.2827(8) Å, β = 95.9744(14)°, V = 694.66(6) ų, Z = 2, R(F) = 0.028, wR(F ²) = 0.070. 4, C₁₆H₁₆N₂O₄Zn, M _r = 365.68, monoclinic, P2₁/c (No. 14), a = 10.6385(5) Å, b = 4.2967(3) Å, c = 15.2844(8) Å, β = 95.941(3)°, V = 694.89(7) ų, Z = 2, R(F) = 0.038, wR(F ²) = 0.107.     

Determination of thermal to epithermal neutron flux ratio (f), epithermal neutron flux shape factor (α) and comparator factor (F<Subscript>c</Subscript>) in the Triga Mark II reactor,Malaysia

The thermal to epithermal neutron flux ratio (f or Ø _th /Ø _e ), epithermal neutron flux shape factor (α) and comparator factor (F _c ) are essential parameters when calculating the concentration of sample using k ₀-standardization method in the neutron activation analysis (NAA). The work was performed in the Triga Mark II reactor of Malaysian Institute for Nuclear Technology Research (MINT) using Au/Zr monitor couple. Twenty channels in the reactor have been evaluated and the corresponding thermal to epithermal neutron flux ratios (f) ranged from 11.69 to 47.89. The epithermal neutron flux shape factors (α) were found in the range of ?1.50·10^?1 to 1.59·10^?1 and the comparator factors (F _c ) were calculated within the range of 9.85·10³ to 6.70·10⁴. These results allowed us to study the neutron flux distribution more precisely and established the goodness of fit for k ₀-NAA.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-[Re<Subscript>6</Subscript>S<Subscript>8</Subscript>(CN)<Subscript>2</Subscript>L<Subscript>4</Subscript>] complexes,L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re₆S₈(CN)₂(py)₄]·H₂O (1), [Re₆S₈(CN)₂(4-Mepy)₄] (2), [Re₆S₈(CN)₂(4-Mepy)₄]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) Å, b = 14.772(1) Å, c = 9.2122(6) Å, β = 119.085(2)°, V = 1761.7(2) ų, d _x = 3.318 g/cm³, R = 0.0585 (1); I4₁/amd space group, a = 16.0018(3) Å, c = 14.7186(5) Å, V = 3768.81(16) ų, d _x = 3.169 g/cm³, R = 0.0489 (2); P2₁/c space group, a = 9.0452(4) Å, b = 15.8065(7) Å, c = 15.2951(6) Å, β = 103.700(2)°, V = 2124.57(16) ų, d _x = 2.957 g/cm³, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.     

X-ray study of rhodium(III) sulfates

Compounds with compositions [Rh(H₂O)₆]₂(SO₄)₃·4H₂O (I), (H₃O)[Rh(H₂O)₆](SO₄)₂ (II), [Rh(H₂O)₅OH](SO₄)·0.5H₂O (III), and [Rh(H₂O)₆]₂(SO₄)·(H₂SO₄) _x ·5H₂O (IV) have been studied. The crystal structures of II, III, and IV were determined. All compounds crystallized in the monoclinic crystal system. Crystal data for II: a = 7.279(2) Å, b = 10.512(7) Å, c = 15.806(3) Å, β = 96.71(3)°, space group P2₁/n, Z = 2, d _calc = 2.334 g/cm³; III: a = 20.433(4) Å, b = 7.820(2) c = 11.215(2) Å, β = 114.14(1)°, space group C2/c, Z = 8, d _calc = 2.559 g/cm³; IV: a = 6.2250(4 Å), b = 27.0270(12) Å, c = 7.2674(5) Å, β = 97.04(3)°, space group P2₁/c, Z = 4, d _calc = 2.143 g/cm³. The compounds were studied by IR spectroscopy and powder X-ray diffraction. All of the isolated crystalline phases are sparingly soluble in ethanol and well soluble in water.