The inductive effect of a radical center and transferability of the properties of functional groups in <Emphasis Type="Italic">n</Emphasis>-alkyl radicals

Electron density distribution in n-alkyl radicals (from ethyl to n-octyl) was studied by the B3LYP/6-311++G(3df,3pd) DFT method. The theory of atoms in molecules was used to show that the inductive effect of a free valence extends to two neighboring CH₂ groups. The electronegativities χ(C^?H₂) > χ(CH₃) > χ(CH₂) of groups and χ(C^?) > χ(H) > χ(C) atoms were qualitatively determined. The group method for calculating the enthalpies of formation of n-alkyl radicals Δ_f H°(n-C _n H_{2n+ 1}, n > 5) was substantiated.     

A Systematic Search for Structures and Stabilities of Asymmetric Clusters (HfInN<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1-6)

In order to find single source precursors (SSP), the structures, relative stabilities, and IR spectra of small asymmetric clusters (HFInN₃) _n (n = 1–6) are systematically investigated by means of the density functional theory at the B3LYP level. The obtained geometries show that the frameworks of clusters (HFInN₃) _n (n = 2–6) prefer to be 2n-membered ring with alternating indium and α-nitrogen atoms. The averaged binding energies reveal that all of asymmetric clusters (HFInN₃) _n (n = 1–6) can continue to gain energy as the cluster size n increasing. The second-order difference of energy (Δ₂E) and the HOMO-LUMO energy gap (E_gap) as a function of the cluster size n both exhibit a pronounced even-odd alternation phenomenon. The influences of cluster size n and temperature T on the thermodynamic properties of clusters are discussed. Judged by enthalpies and Gibbs free energies, the formations of the most stable clusters (HFInN₃) _n (n = 2–6) from the monomer are thermodynamically favorable in the range of 200–800 K.     

Optical Band Gap Energies in Quasi-Metal Carbon Nanotubes

The structure of carbon nanotubes is described by two positive integers (n₁, n₂). The π-electron model of the nanotube band structure predicts that when the difference n₁–n₂ is multiple of three, the energy gap between the valence and conduction bands vanishes so that such tubes should exhibit quasi-metal properties. The band structure of 50 chiral and achiral (n₁, n₂) nanotubes with 4 ≤ n₁ ≤ 18 and n₂ = n₁–3q has been calculated by the linearized augmented cylindrical wave method. Nanotubes have been identified for which the optical band gaps are in the terahertz range (1–40 meV) and which can be used for design of emitters, detectors, multipliers, antennas, transistors, and other nanoelements operating in the high-frequency range.     

Determination of the molecular masses of tetrafluoroethylene telomers by gel-permeation chromatography

Gel-permeation chromatography has been employed to study the molecular-mass distribution of tetrafluoroethylene telomers prepared through γ irradiation of 0.05–0.56 mol/l monomer solutions in acetone. The molecular-mass-retention-volume V _R calibration dependence has been plotted from chromatograms of perfluoroenanthic and perfluoropelargonic acids (F(CF₂-CF₂) _n COOH; n = 3 or 4, respectively). The measured V _R-log n curve is located parallel to that plotted earlier for oligo(oxyethylene glycol)s (OH-(CH₂-CH₂O) _n -OH) and is shifted along the volume axis. The shift value is determined by the ratio between logarithmic volumes of chain units of these oligomers. The shift agrees with the assumption that the retention volumes of oligomers with the same spatial chain structure are proportional to the logarithm of the ratio between their van der Waals volumes. This assumption is supported by the quantum-chemical calculation of the molecular volumes of oligomers composed of (CH₂-CH₂) _n , (CH₂-CH₂O) _n , and (CF₂-CF₂) _n fragments. As the concentration of tetrafluoroethylene in the initial solution is increased, the average length of (CF₂-CF₂) _n chains increases from \(\bar n\) ≈ 3 to \(\bar n\) ≥ 8. The maximum values of n = 12–15 are determined by the solubility limit of telomers in THF.     

Kinetics of Isothermal Pyrolysis of Iodomethanes in the Gas Phase

The limiting step of the isothermal pyrolysis of gaseous iodomethane (CH₃I → 3/4CH₄ + 1/2I₂ + 1/(4n)C _n ) and diiodomethane (CH₂I₂ → 1/2CH₄ + I₂ + 1/(2n)C _n ) are the reactions 2CHI → C₂ + 2HI and 2CI₂ → C₂ + 2I₂, respectively. The rate constants of these reactions were determined.     

Adsorption Properties of Thiocontaining Schungite

Chromatography–mass spectrometry and thermodesorption mass spectrometry have been employed to study mineral schungite-III, in which various thiocompounds have been detected and identified. The influence of these compounds on the adsorption activity of schungite with respect to iodine has been investigated. It has been shown that sulfur present in schungite has no effect on the results of determining its adsorption activity and does not interact with iodine; however, it can interact with amino compounds to yield sulfides. Activation energies E_a have been experimentally determined for sulfur, iodine, and dimethyl disulfide desorption from the surfaces of schungite and a model sorbent, graphitized thermal carbon black. The E_a values of these compounds have appeared to be several times lower than the heats of their adsorption on carbon black calculated by the molecular-statistical method.     

Electron affinity and substituent effects in radical anions

The first vertical electron affinities EA of 13 series of molecules and free radicals D(X _i ) _n are related to the inductive (σ _I ), resonance (σ _R ^? ), and polarization (σ_α) parameters of substituents X _i by the dependences EA = EA _H + aΣσ _I + bΣσ _R/? + cΣσ_α: In radical anions D^+·(X _i ) _n , compared to radical cations D^+·(X _i ) _n , the polarization interaction is weaker or similar in magnitude but has an opposite sign. The previously unknown resonance parameters σ _R ^? of substituents SiMe₃ and CH₂SiMe₃ bound to the radical anion center H₂C=CH^?· were calculated.     

The molecular designs and properties of asymmetric heterocycles (HBrBN<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1-4)

The structures and properties of asymmetric heterocycles (HBrBN₃) _n (n = 1-4) are systematically studied at the B3LYP/6-31G* level. The molecules (HBrBN₃) _n (n = 2-4) have the core structures of a 2n-membered ring with alternating boron and α-nitrogen atoms. The relationships between geometrical parameters and oligomerization degree n are discussed. The calculated IR spectra have four main characteristic regions. Trends in thermodynamic properties with temperature and oligomerization degree n are discussed. Thermodynamic analysis of the gas-phase oligomerizations shows that formation of the most stable heterocycles (HBrBN₃) _n (n = 2-4) is enthalpy driven in the range of 200-800 K.     

Search for the structures,stabilities, IR spectra,and thermodynamic properties of the asymmetric clusters (HClBN<Subscript>3</Subscript>)<Subscript> <Emphasis Type="Italic">n</Emphasis> </Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1–6)

The density functional theory (DFT) method has been employed to systematically investigate the geometrical structures, stabilities, IR spectrum and thermodynamic properties of small asymmetric clusters (HClBN₃)_n (n = 1–6). When n ≥ 2, the optimized results suggest that the (BN_α)_2n cyclic structures with alternating boron and α-nitrogen atoms are observed in clusters. The influences of cluster size on the structures of clusters were discussed. The second-order difference in energies show that the (HClBN₃)₃ isomer is the most stable among the asymmetric clusters (HClBN₃)_n. Four main characteristic regions are obtained and assigned for the calculated IR spectra. A study of their thermodynamic properties suggests that monomer 1 forms clusters (2–6) thermodynamically favorable by the enthalpies at 298.2 K.     

Random packing of monoatomic structures

The dependence of the first coordination number k _n on the packing factor k _y is obtained for four cubic structures: fcc, bcc, simple cubic, and diamond. The k _n (k _y ) dependence is described by a third-degree polynomial k _n = ?71.76782 + 467.78914 k _y ? 925.48451 k _y ² + 603.01146 k _y ³ with the confidence factor R _d = 1. The k _n (k _y ) function has an N loop with a maximum at k _n = 6.32; k _y = 0.454 and a minimum at k _n = 5.84; k _y = 0.573. The tangents intersect the k _n (k _y ) curve at extrema at k _y = 0.4 and k _y = 0.625. Around the N loop, i.e., at 5.84 ≤ k _n ≤ 6.32 and 0.4 ≤ k _y ≤ 0.625, two or three packing factors correspond to a certain value of the coordination number. Therefore, this range of the k _n and k _y values can be defined as a “random packing” region. Estimations presented here agree well with the results of calculations, both geometric and numerical. For monoatomic solids with the random packing parameters, the difference between the specific volumes of the solid and liquid phases is insignificant. The dilatancy effect is possible in the region where ?k _n / ?k _y ≤ 0.     

Synthesis of Polyfluorinated Ethers

Procedures for preparing polyfluorinated ethers H(CF₂CF₂) _n CH₂OR by alkylation of the corresponding telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1–3) with alkyl halides and alkyl tosylates were examined.     

Synthesis and structure of Pt(II) acetamidate complexes containing <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-substituted ethylenediamine and trimethylenediamine

Reactions of acetamide with platinum(II) diamines [Pt(N,N-DimeEn)Cl₂], [Pt(Tm)Cl₂], and [Pt(N,N-DimeTm)Cl₂] (N,N-DimeEn = (CH₃)₂N(CH₂)₂NH₂, Tm = NH₂(CH₂)₃NH₂, N,N-DimeTm = (CH₃)₂N(CH₂)₃NH₂) with preliminary precipitation of chlorine ions by silver salts gave binuclear Pt(II) acetamidates [Pt₂(CH₃)₂N(CH₂)₂NH₂)₂(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (I), [Pt₂(NH₂(CH₂)₃NH₂)₂)(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (II), and [Pt₂(CH₃)₂N(CH₂)₃NH₂)₂(μ-NHCOCH₃)₂](HSO₄)₂ (III), whose crystal structures were determined. Crystals of I are monoclinic: a = 14.459(2) Å, b = 17.197(3) Å, c = 9.822(2) Å, β = 105.923(10)°, V = 3348.6(8) ų, space group P2(1)/c, Z = 4, R _hkl = 0.0419 for 6663 reflections. Complex I is a binuclear acetamidate with bridging (NHCOCH₃)^? ligands, one of which is bound to two Pt atoms through the N and O atoms, and the other ligand is bound only through the N atom. The Pt-Pt distance is 2.987(1) Å. Crystals of II are monoclinic: a = 10.213(7) Å, b = 13.373(9) Å, c = 16.533(11) Å, β = 97.971(9)°, V = 2236(3) ų, space group P2(1)/n, Z = 4, R _hkl = 0.557 for 6462 reflections. The Pt-Pt distance is 3.057(1) Å. Crystals of III are monoclinic: a = 10.557(12) Å, b = 18.531(2) Å, c = 14.4744(17) Å, β = 108.705(2)°, V = 2682(5) ų, space group P2(1)/n, Z = 4, R _hkl = 0.569 for 8506 reflections. The Pt-Pt distance is 3.202(1) Å. Complexes II and III are binuclear acetamidates, in which two chelating Pt(Tm) or Pt(N,N-DimeTm) moieties are coordinated through the N and O atoms of (NHCOCH₃)^? cis-bridges.     

Complexing and extraction of palladium(II) by <Emphasis Type="Italic">n</Emphasis>-alkyl(tolyl)thiamethylcalix[4]arenes from chloride solutions

Complexing [PdCl₄]^2? with calix[4]arenes (L) functionalized by CH₂SR (R = Me (1), n-Bu (2), or p-Tol (3)) in their upper rims has been studied in toluene and CCl₄. The stoichiometry of the extracted palladium species (PdCl₂) _n L, where n = 1 or 2 is established by spectroscopic methods (NMR spectroscopy, UV/Vis spectrophotometry, atomic absorption) and extraction. For slow coordinative extraction, the concentration constants of complex formation and extraction from chloride solutions are determined using the coupled equilibria method. The kinetic and thermodynamic laws of extraction coincide, and their parameters increase in the following row of the substituents at the sulfur atom: p-Tol < Bu < Me.     

Alkali (alkaline-earth) metal,aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A_{1 + x} Al _x Ti_{2 ? x} P₃O₁₂ (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} P₃O₁₂ (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A_{1 + x} Al _x Ti_{2 ? x} (PO₄)₃ with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} (PO₄)₃ with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi₂(PO₄)₃ (x = 0), Rietveld refinement was carried out: space group Ia \(\bar 3\) d, Z = 32, a = 19.909(5) Å, V = 7892(1) ų. This compound has a framework structure. The framework is built of TiO₆ octahedra and PO₄ tetrahedra; eight- and 12-coordinated Cs⁺ cations populate interstices.     

Synthesis,characterization, antimicrobial activity and ultrastructure of the affected bacteria of new quinoline compounds

The reaction on 8-hydroxy quinoline-7-aldehyde azo compounds (HL _n ) (where n = 1–5) with 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one to obtain HL _n (where n = 6–10) have been characterized by means of TLC, melting point and spectral data, such as IR, ¹H NMR, mass spectra and thermal studies. The X-ray diffraction patterns of two starting materials 8-hydroxy quinoline-7-aldehyde (start 1), 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (start 2) and the ligands (HL_5,10) are investigated in powder form. All the ligands have been screened for their antimicrobial activity against four local bacterial species, two Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) as well as against four local fungi; Aspergillus niger, Alternaria alternata, Penicillium italicum and Fusarium oxysporium. The results show that the azo ligands (HL _n ) (where n = 1–5) have no antimicrobial activity against bacteria and fungi while most azomethine ligands (HL _n ) (where n = 6–10) are good antibacterial agents against E. coli and K. pneumoniae as well as antifungal agents against P. italicum and A. alternata. The results were compared to standard substances (start 1) and (start 2). Among the azomethine ligands, HL₁₀ was the most effective against the most microorganisms tested. The size of clear zone was ordered as p-(OCH₃ < CH₃ < H < Cl < NO₂) as expected from Hammett’s constant (σ ^R ). Also, the ultrastructure study of the affected bacteria confirmed that HL₈ is good antibacterial agent against E. coli and S. aureus.     

New carborane-containing acids and amines

Alkylation of nido-carborane methyl sulfide derivative [9-MeS-7,8-C₂B₉H₁₁]^– was used to synthesize a series of new carborane-containing acids 9-HOOC(CH₂) _n (Me)S-7,8-C₂B₉H₁₁ (n = 1—4) and amines 9-H₂N(CH₂) _n (Me)S-7,8-C₂B₉H₁₁ (n = 2, 3). The compounds obtained can be used for the development of BNCT agents.     

Systems Li<Subscript>2</Subscript>O(Na<Subscript>2</Subscript>O)-CdO-V<Subscript>2</Subscript>O<Subscript>5</Subscript>: Phase composition and phase diagrams

The subsolidus phase composition of the M₂O-CdO-V₂O₅ systems with M = Li or Na is studied. Double orthovanadates MCdVO₄ and MCd₄(VO₄)₃ form solid solutions of composition Li_{1 ? 2x/3}Cd _x/3CdVO₄ (0 ≤ x ≤ 1, orthorhombic space group Cmcm, modulation at x = 0.6) and Na_{3 ? 2x} Cd_{3 + x} (VO₄)₃ (0 ≤ x ≤ 0.10 and 0.30 ≤ x ≤ 1, orthorhombic space group Cmcm and Pn2₁ a or Pnma, respectively). In the range 0.10 < x < 0.30, the end-members of the solid solutions coexist. Isothermal sections of the systems are mapped.     

Synthesis and crystal structure of the equimolar complex of copper(I) cyanide with 3,3′-[ethane-1,2-diylbis(oxy)]dipropanenitrile

Complex [Cu(CN)(NC(CH₂)₂O(CH₂)₂O(CH₂)₂CN))] is obtained by the heating of copper(I) cyanide with 3,3′-[ethane-1,2-diylbis(oxy)]dipropanenitrile (DPN) followed by slow cooling. The X-ray diffraction analysis shows that the crystals are monoclinic, space group C2/c, a = 12.183(2), b = 10.667(2), c = 8.4700(13) Å, β = 92.444(10)°, V = 1099.7(3) ų, Z = 4. The structure is built of infinite zigzag fragments [Cu(CN)(DPN)] _n . The tetrahedral environment of the copper atom includes two cyano groups of the ligand and two cyano groups of the inorganic fragment.     

Silicon-containing dimethylphosphoric acid amides

α-Silylmethylamines MeNHCH₂SiMen(OMe)_3?n (n=0, 2) were involved into Todd-Atherton reaction with (MeO)₂P(O)H giving N-methyl-N-trimethoxysilylmethyl-and N-methyl-N-dimethyl-(methoxy)silylmethylamides of dimethylphosphoric acid. A reaction of these compounds with BF₃·Et₂O led to the formation of the corresponding N-methyl-N-trifluoro-and N-methyl-N-(dimethyl)fluorosilylmethylamides of dimethylphosphoric acid. (MeO)₂P(O)N(Me)CH₂SiF₃ existed as an (O-Si)-chelate with a pentacoordinate silicon due to the occurrence of a rare and unstudied intramolecular coordinating interaction P=O → Si.     

Kinetics of the formation of precipitates and the physicochemical properties of technetium-99 and rhenium sulfides according to small-angle X-ray scattering and ultramicrocentrifugation data

The interaction of technetium and rhenium with sulfides in aqueous solutions was studied by small-angle X-ray scattering and ultramicrocentrifugation. It was shown that, although the stoichiometry of technetium sulfide corresponds to the formula Tc₂S_7–x, the oxidation state of technetium in it is +4 and the excess sulfur is bound into a disulfide group so that its formula can correctly be written as [Tc₃(µ³-S)(µ²-S₂)₃(S₂)_(3n–n)/n)]_n. The determination of the solubility of technetium sulfide is complicated by its tendency to form colloids, which was the reason why the above methods were chosen to find features of its formation and describe its solubility in solutions.