A DFT study of reduction of nitrobenzene to aniline with SnCl2 and hydrochloric acid

A fundamental reduction reaction, nitrobenzene to aniline in SnCl₂ and hydrochloric acid, was investigated by density functional theory (DFT) calculations. First, the change of SnCl₂ → SnCl₄^2? → Cl₄SnH^? was discussed, and the reaction path of SnCl₄^2? + H₃O⁺ → Cl₄SnH^? + H₂O was obtained. Starting from nitrobenzene, six elementary processes were found so as to arrive at the protonated aniline. The hydride ion from Cl₄SnH^? is connected always to the cationic nitrogen, and the proton is always to oxygens. An intermediate Ph?N⁺H₂OH was obtained, which is isomerized to the para O?H adduct protonated imine via the Bamberger rearrangement. This species may undergo the H^? acceptance at the sp² N⁺H₂ center. In the nitrobenzene reduction, the proton enhances the electrophilicity of the nitrogen center, which makes the hydride shift ready. N?H bonds are formed, and N?O bonds are cleaved both by the proton attach and subsequent H₂O elimination and by the formal [1,5] OH shift. Copyright © 2016 John Wiley & Sons, Ltd.     

FT-IR and Raman spectra and vibrational investigation of bis (4-acetylanilinium) hexachlorostannate using DFT (B3LYP) calculation

4-acetylanilinium was used as a ligand for the synthesis of the organic/inorganic compound bis (4-acetylanilinium) hexachlorostannate. Vibrational study in the solid state was performed by FT-Raman of the free 4-acetylanilinium ligand C₈H₉ON⁺ and by FT-IR and FT-Raman spectroscopies of the [C₈H₁₀NO]₂ SnCl₆ compound. The comparative analysis of the Raman spectra of the title compound with that of the free ligand was discussed. The structure of the [C₈H₁₀NO]₂SnCl₆ was optimized by density functional theory (DFT) using B3LYP method and shows that the calculated values obtained by B3LYP/LanL2DZ basis are in a better agreement with the experimental data reported by Song et al. (2011) [1] than those obtained by B3LYP/LanL2MB basis. The vibrational frequencies are calculated using density functional theory (DFT) with the B3LYP/LanL2DZ basis, and scaled by various factors. Root mean square (RMS) value was calculated and the small difference between experimental and calculated modes has been interpreted by intermolecular interactions in the crystal.     

Study of chemical shift in Ll and Lƞ X‐ray emission lines in different chemical forms of 48Cd and 50Sn compounds using WDXRF technique

Chemical shift in Ll and L? X‐ray emission lines of ₄₈Cd and ₅₀Sn elements in various chemical compounds was determined with high resolution wavelength dispersive X‐ray fluorescence (WDXRF) spectrometer. The positive and negative shifts were measured in ₄₈Cd compounds viz, CdS, CdB₄O₇, CdCl₂, Cd₃(PO₄)₂, CdCO₃, CdI₂ and CdO with reference to pure Cd foil and ₅₀Sn compounds viz, Sn(CrO₄)₂, SnO, SnO₂, SnCl₂, SnF₂, SnF₄ with reference to pure Sn foil. The measured energy shifts in Ll X‐ray emission lines range from ?0.47 to 1.82 eV and L? emission lines range from ?2.67 to 1 eV for both compounds. The effective charges (q, q ^/ , q ^// , and q ^/// ) were calculated from four models (Pauling method, Suchet method, Levine method and Batsonav method) and found to be linear dependence with chemical shift. The measured chemical shifts were correlated with effective charge, number of ligands and electronegativity of the central metal atom in the given compounds.     

Structural characterization,spectroscopic, thermal,AC conductivity and dielectric properties and antimicrobial studies of (C8H12N)2[SnCl6]

A new inorganic-organic hybrid material produced from 2,6-dimethylanilinium cations and tin halide (SnCl₆)^2? has been synthesized and structurally determined by X-ray diffraction method. The title compound crystallizes in the monoclinic system, space group C2/m with a = 19.8772(4), b = 6.9879(1), c = 8.3001(2) Å, β = 98.487(2)° and V = 1140.26(4) ų. The crystal structure is built up of sheets of (SnCl₆)^2? octahedral anions and 2,6-xylidinium cations. The optical band gap was calculated and found to be 4.11 eV. At high temperature this compound exhibits a structural phase transition at 338 K. This has been characterized by differential scanning calorimetric and dielectric studies. Measurements of AC conductivity as a function of frequency at different temperatures indicated the hopping conduction mechanism. The bioassay results showed that the structure exhibits significant antibacterial activity.     

Synthesis of novel 4H-pyrimido[1,6-a]pyrimidines via a one-pot three-component condensation

Abstract  

Highly substituted novel 4H-pyrimido[1,6-a] pyrimidines were prepared by a trifluoromethanesulfonic acid catalyzed one-pot three-component condensation of 4-aminopyrimidines, aldehydes, and β-ketoesters. A preliminary feasibility study was undertaken on these compounds, to assess the potential production of a library of further diversified compounds by nucleophilic replacement of Cl (R¹) or by reaction of electrophiles with the NH₂ (R²) group.     

A 119Sn Mössbauer Spectroscopic Investigation of Tin Complexes with Amidines

Several novel tin(IV) adducts of amidines, [SnClPh₃L], [SnCl₂Ph₂L] and [SnBr₄L] {L=N,N-diphenylacetamidine (Hdpac) or N,N-diphenylbenzamidine (Hdpba)}, were prepared and investigated by Mössbauer spectroscopy which was an important tool for the elucidation of bonding and structural features. The resulting Mössbauer data also led to the conclusion that the tin(IV) centre for the adduct [SnClPh₃L] is pentacoordinated in a trigonal bipyramidal arrangement and hexacoordinated for [SnCl₂Ph₂L] and [SnBr₄L] in a geometric patterns of an octahedral. The amidines act as monodentate ligands to the metal centre for the former and bidentate for the latter.     

Structural characterization,thermal, ac conductivity and dielectric properties of (C7H12N2)2[SnCl6]Cl2·1.5H2O

(C₇H₁₂N₂)₂[SnCl₆]Cl₂·1.5H₂O is crystallized at room temperature in the monoclinic system (space group P2₁/n). The isolated molecules form organic and inorganic layers parallel to the (a, b) plane and alternate along the c-axis. The inorganic layer is built up by isolated SnCl₆ octahedrons. Besides, the organic layer is formed by 2,4-diammonium toluene cations, between which the spaces are filled with free Cl^? ions and water molecules. The crystal packing is governed by means of the ionic N—H···Cl and Ow—H···Cl hydrogen bonds, forming a three-dimensional network. The thermal study of this compound is reported, revealing two phase transitions around 360(±3) and 412(±3) K. The electrical and dielectric measurements were reported, confirming the transition temperatures detected in the differential scanning calorimetry (DSC). The frequency dependence of ac conductivity at different temperatures indicates that the correlated barrier hopping (CBH) model is the probable mechanism for the ac conduction behavior.     

Complete basis set,hybrid‐DFT study and NBO interpretations of conformational behaviors of trans‐2,3‐ and trans‐2,5‐dihalo‐1,4‐dithianes

The conformational behaviors of trans‐2,3‐dihalo‐1,4‐dithiane [halo = F ( 1 ), Cl ( 2 ), Br ( 3 )] and trans‐2,5‐dihalo‐1,4‐dithiane [halo = F ( 4 ), Cl ( 5 ), Br ( 6 )] have been analyzed by means of complete basis set CBS‐4, hybrid‐density functional theory (B3LYP/6‐311 + G**//B3LYP/6‐311 + G**) based methods, and natural bond orbital (NBO) interpretation. Both methods showed that the axial conformations of compounds 1–5 are more stable than their equatorial conformations but CBS‐4 resulted in an equatorial preference for compound 6 . The Gibbs free energy difference (G_eq?G_ax) values (i.e., ΔG_eq–ax) at 298.15 K and 1 atm between the axial and equatorial conformations decrease from compound 1 to compound 2 but increase from compound 2 to compound 3 . Also, the calculated ΔG_eq–ax values decrease from compound 4 to compound 6 . The NBO analysis of donor–acceptor (LP → σ*) interactions showed that the anomeric effect (AE) increase from compound 1 to compound 3 and also from compound 4 to compound 6 . On the other hand, the calculated dipole moment values between the axial and equatorial conformations [Δ(µ_eq?µ_ax)] decrease from compound 1 to compound 3 . The conflict between the increase of AE and the decrease of Δ(µ_eq?µ_ax) values could explain the variation of the calculated ΔG_eq–ax for compounds 1–3 . The Gibbs free energy difference values between the axial and equatorial conformations (i.e., ΔG_ax–ax and ΔG_eq–eq) of compounds 1 and 4 , 2 and 5 and also 3 and 6 have been calculated. The correlations between the AE, bond orders, pairwise steric exchange energies (PSEE), ΔG_eq–ax, ΔG_ax–ax, ΔG_eq–eq, dipole–dipole interactions, structural parameters, and conformational behaviors of compounds 1–6 have been investigated. Copyright © 2010 John Wiley & Sons, Ltd.     

Solid‐phase cadmium speciation in soil using L3‐edge XANES spectroscopy with partial least‐squares regression

Cadmium (Cd) has a high toxicity and resolving its speciation in soil is challenging but essential for estimating the environmental risk. In this study partial least‐square (PLS) regression was tested for its capability to deconvolute Cd L₃‐edge X‐ray absorption near‐edge structure (XANES) spectra of multi‐compound mixtures. For this, a library of Cd reference compound spectra and a spectrum of a soil sample were acquired. A good coefficient of determination (R²) of Cd compounds in mixtures was obtained for the PLS model using binary and ternary mixtures of various Cd reference compounds proving the validity of this approach. In order to describe complex systems like soil, multi‐compound mixtures of a variety of Cd compounds must be included in the PLS model. The obtained PLS regression model was then applied to a highly Cd‐contaminated soil revealing Cd₃(PO₄)₂ (36.1%), Cd(NO₃)₂·4H₂O (24.5%), Cd(OH)₂ (21.7%), CdCO₃ (17.1%) and CdCl₂ (0.4%). These preliminary results proved that PLS regression is a promising approach for a direct determination of Cd speciation in the solid phase of a soil sample.     

N‐Chlorination rate of five‐membered heterocyclic nitrogen compounds

The kinetics of N‐chlorination reaction of pyrrolidine, pyrrolidone, succinimide, 5,5,‐dimethyloxazolidine‐2,4‐dione, 5,5‐dimethylhydantoin and 1‐hydroximethyl‐5,5‐dimethylhydantoin with HOCl in aqueous solution were studied at 25 °C, constant ionic strength and under isolation conditions in a wide pH range. The set of compounds studied in this paper is characterized by having different functional groups and the same cyclic structure, consisting of a five‐member ring with a nitrogen atom in the ring, which is susceptible to be chlorinated. This series of compounds covers nine pK_a units, and the kinetic studies allow us to know, like, the presence of an amino, amide or imide group modify the reactivity of nitrogenous compound. Experimental data were fitted to the first‐order kinetic equation. All reactions were found to be of first order in both HOCl and nitrogenous compound concentration. Kinetics studies demonstrate that some of these compounds are hydrolyzed in alkaline medium. In each case, reaction mechanism in agreement with the experimental results is proposed. The results were compared with other compounds with similar cyclic structure (2‐oxazolidinone and proline). Copyright © 2016 John Wiley & Sons, Ltd.     

On Mössbauer effect in polypyrrole doped with selected metal halides

The reaction of partially oxidized polypyrrole [(C₄H₃N)₄⁺Cl₋]_n with FeCl₃ and SnCl₄ leads to the insertion of only one type metal halide species namely FeCl₄⁻ and SnCl₅⁻. The reaction with stannic halide is acid-base in nature whereas the reaction with ferric chloride may be either redox or acid-base. The use of SbCl₅ results in the insertion of two non-equivalent antimony halide species: SbCl₆⁻ and SbCl₃. Much simpler Mössbauer spectra can be obtained if in the doping reactions SbCl₅ or SbF₅ are replaced by NO₂⁺SbF₆⁻. Only one type of antimony with Mössbauer parameters characteristics of SbF₆⁻ is observed in this case. The Mössbauer lattice temperatures, θ_M, calculated from the temperature dependence of the recoil free fractions are 94 K and 105 K for FeCl₃ and SnCl₄ doped polypyrrole respectively. The obtained values are within the range typically observed for other conducting polymeric systems.     

The crystal structures and physical properties of the solid solution compound Ba5Y8-xMn4O21-1.5x (x=0, 1)

New oxometallides with the formula Ba5Y8 xMn4O21 1.5x(x = 0,1) are prepared through an atmospherecontrolled solid-state reaction.Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4(Y8) and 5/7/4(Y7) are obtained.The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction,magnetization,conductivity,and dielectricity measurements.The Ba5Y8 xMn4O21 1.5x compound is demonstrated to be a Y-deficient solid solution.The solid solution compound Ba5Y8 xMn4O21 1.5x crystallizes into tetragonal symmetry with the space group I4/m.Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y(2) site.Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds,and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples,respectively.Strong frequency dependences of the dielectric constant are observed above ～175 K for the two compounds.     

Synthesis and mesomorphism of 2,5-bis(3,4-bis(n-alkoxy)phenyl)thiazolo[5,4-d]thiazole tetracatenar liquid crystals

A series of new symmetrical 2,5-bis(3,4-bis(n-alkoxy)phenyl)thiazolo[5,4-d]thiazoles (TTn) prepared via condensation of dithiooxamide with six different 3,4-di-n-alkoxybenzaldehydes were characterized by ¹H NMR, FTIR, UV-Vis, and photoluminescence spectroscopy. Moreover, one compound lack of aliphatic chains, i.e., 2,5-diphenylthiazolo[5,4-d]thiazole (TT) was synthesized and characterized. The investigated TTn compounds emitted blue light. The effect of length of n-alkoxy (i.e., OC _n H_{2 n +1}, n?=?8, 10, 12, 14, 16, and 18) peripheral groups on thermal and mesomorphic behavior was investigated by means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. Variable heating and cooling rates were used to study the liquid-crystalline properties of TTn. All compounds exhibited liquid-crystalline properties which self-organize into one or two smectic mesophases (SmB and SmE).     

Sonochemical preparation of SnS and SnS2 nano- and micropowders and their characterization

Sonochemical production of tin(II) and tin(IV) sulfides is investigated. Different conditions of syntheses are examined: used solvent (ethanol or ethylenediamine), source of tin (SnCl₂ or SnCl₄), the molar ratio of thioacetamide to the tin source, and time of sonication. The obtained powders are characterized by the X-ray diffraction method (PXRD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and the Tauc method. Raman and FT-IR measurements were performed for the obtained samples, which additionally confirmed the crystallinity and phase composition of the samples. The influence of experimental conditions on composition (is it SnS or SnS₂), morphology, and on the bandgap of obtained products is elucidated. It was found that longer sonication times favor more crystalline product. Each of bandgaps is direct and most of them show typical values – c.a. 1.3 eV for SnS and 2.4 eV for SnS₂. However, there are some exceptions. Synthesized powders show a variety of forms such as needles, flower-like, rods, random agglomerates (SnS₂) and balls (SnS). Using ethanol as a solvent led to powders of SnS₂ independently of which tin chloride is used. Sonochemistry in ethylenediamine is more diverse: this solvent protects Sn²⁺ cations from oxidation so mostly SnS is obtained, while SnCl₄ does not produce powder of SnS₂ but Sn(SO₄)₂ instead or, at a higher ratio of thioacetamide to SnCl₄, green clear mixture.     

Conformational analysis of 4,4‐dimethyl‐1‐(trifluoromethylsulfonyl)‐1,4‐azasilinane and 2,2,6,6‐tetramethyl‐4‐(trifluoromethylsulfonyl)‐1,4,2,6‐oxazadisilinane

4,4‐Dimethyl‐1‐(trifluoromethylsulfonyl)‐1,4‐azasilinane 1 and 2,2,6,6‐tetramethyl‐4‐(trifluoromethylsulfonyl)‐1,4,2,6‐oxazadisilinane 2 were studied by variable temperature dynamic ¹H, ¹³C, ¹⁹F NMR spectroscopy and theoretical calculations at the DFT (density functional theory) and MP2 (Møller‐Plesset 2) levels of theory. Both kinetic (barriers to ring inversion) and thermodynamic data (frozen conformational equilibria) could be obtained for the two compounds. The computations revealed two minima on the potential energy surface for molecules 1 and 2 corresponding to the rotamers with the CF₃SO₂ group directed ‘inward’ and ‘outward’ the ring, the latter being 0.2–0.4 kcal/mol (for 1 ) and 1.1 kcal/mol (for 2 ) more stable than the former. The vibrational calculations at the DFT and MP2 levels of theory give the values of the free energy difference ΔG^o for the ‘inward’ ‘outward’ equilibrium consistent with those determined from the experimentally measured ratio of the rotamers. The structure of crystalline compound 2 was ascertained by X‐ray diffraction analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

Two Mn(II) and Zn(II) Coordination Polymers: Aqueous-Phase Detection of Nitroaromatic Explosives and Protective Effect on Atherosclerosis

Via the solvothermal reaction between Zn(II) or Mn(II) salts and 5-(3,4-dicarboxylphenoxy)nicotinic acid (H₃L) ligand, a trifunctional N,O-building block having three diverse kinds of functional groups (O-ether, N-pyridyl and COOH), two new coordination polymers (CPs) could be generated, and their chemical formulae respectively are {[Mn₃(L)₂(H₂O)₂]·4H₂O} (1) and {[Zn(HL)]·NMP} (2). The complex 2 based on Zn(II) possesses high efficiency of fluorescence quenching for the nitrophenol (2,4,6-trinitrophenol, TNP; 4-nitrophenol, 4-NP; 3-nitrophenol, 3-NP; 2-nitrophenol, 2-NP) in the aqueous solution. Furthermore, the treatment activity of compounds on the atherosclerosis was assessed, and relevant mechanism was investigated. First of all, the ELISA assay was used to measure the content of the inflammatory cytokines released into the plasma. Besides, the levels of the NF-κb signaling pathway in the vascular endothelial cells were measured with real time RT-PCR. The hemolysis test was conducted in this research to measure the biocompatibility of the new compound.

     

Crystal structure of ethyl (2Z)-2-(3-methoxy-4-acetyloxy benzylidene)-7-methyl-3-oxo-5-phenyl-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate

The title compound, C₂₆H₂₄N₂O₆S, (I), crystallizes in the monoclinic space group, P2₁/c, with cell parameters a = 16.248(1), b = 7.927(1), c = 19.371(4) ?, β = 105.295(2)°, Z = 4. The central pyrimidine ring in the compound (I) is significantly puckered, assuming a screw-boat conformation. The C11–C16 benzene ring stands vertical while thiazole and C18–C23 benzene rings are coplanar to the mean plane of pyrimidine ring having dihedral angles of 87.48(12), 3.63(11) and 0.94(12)°, respectively. In the absence of potential hydrogen bonding interaction, the crystal packing is influenced by intramolecular C-H…S interaction and intermolecular C-H…π interactions.     

Effect of N-substitution in multinuclear complexes allows interplay between magnetic states and multistability investigated by Mössbauer spectroscopy

A series of pentadentate ligands N–X–⁵LH₂ (X?=?H, Methyl, Benzyl)?=?N–X–saldptn (4-X-N,N′-bis(1-hydroxy-2-benzylidene)-1,7-diamino-4-azaheptane) has been prepared by a Schiff base condensation between 1,7-diamino-4-X-azaheptane and salicylaldehyde. Complexation with Fe(III) yields a series of high-spin (S?=?5/2) complexes of [Fe^III(N–X–⁵L)Cl]. Such precursors were combined with [Mo(CN)₈]^4? and a series of blue nonanuclear cluster compounds [Mo^IV{(CN)Fe^III(N–X–⁵L)}₈]Cl₄ resulted. Such star-shaped nonanuclear compounds are high-spin systems at room temperature. On cooling to 10 K some of the iron(III) centers switched to the low-spin state as proven by Mössbauer spectra, i.e. multiple electronic transitions. Parts of the compounds perform a high-spin to high-spin transition. Under light irradiation the populations are altered slightly.     

Sonochemical synthesis,characterization, and effects of temperature,power ultrasound and reaction time on the morphological properties of two new nanostructured mercury(II) coordination supramolecule compounds

Two new mercury(II) coordination supramolecular compounds (CSCs) (1D and 0D), [Hg(L)(I)₂]_n (1) and [Hg₂(L′)₂(SCN)₂]·2H₂O (2) (L = 2-amino-4-methylpyridine and L′ = 2,6-pyridinedicarboxlic acid), have been synthesized under different experimental conditions. Micrometric crystals (bulk) or nano-sized materials have been obtained depending on using the branch tube method or sonochemical irradiation. All materials have been characterized by field emission scanning electron microscope (FESEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and FT-IR spectroscopy. Single crystal X-ray analyses on compounds 1 and 2 show that Hg²⁺ ions are 4-coordinated and 5-coordinated, respectively. Topological analysis shows that the compound 1 and 2 have 2C1, sql net. The thermal stability of compounds 1 and 2 in bulk and nano-size has been studied by thermal gravimetric (TG), differential thermal analyses (DTA) for 1 and differential scanning calorimetry (DSC) for 2, respectively. Also, by changing counter ions were obtained various structures 1 and 2 (1D and 0D, respectively). The role of different parameters like power of ultrasound irradiation, reaction time and temperature on the growth and morphology of the nano-structures are studied. Results suggest that increasing power ultrasound irradiation and temperature together with reducing reaction time and concentration of initial reagents leads to a decrease in particle size.     

X-ray, scanning electron microscopy and electrical properties of synthetic fresnoite (Ba2TiSi2O8) ceramics

Polycrystalline ceramic samples of fresnoite (Ba₂TiSi₂O₈ or BTS) have been prepared by a standard solid-state reaction method using high-purity oxides and carbonates. For one set of compounds, in stoichiometric ratio BaCO₃, TiO₂ and SiO₂ were melted at 1300°C and then sintered into pellet form, whereas the other set of compounds have been prepared without melting and sintered into pellet form at 1250°C. The formation of the single-phase compound and its structural parameters were investigated by X-ray diffraction followed by Rietveld refinement and scanning electron microscopic (SEM) techniques. A better agreement between the observed and calculated X-ray diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group P4bm. A better agreement between observed and calculated d-values shows that the lattice parameters calculated using the Rietveld refinement analysis are better than that of the earlier report so far. The activation energies of both compounds were calculated by measuring its dc electrical conductivities. The results are discussed in detail.