A thermodynamic study of interaction of Ag+, Mg2+, Ca2+, and K+ cations with 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine in some binary mixed non-aqueous solvents

In the present work the complexation process between Ag⁺ and Mg²⁺ cations and 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine (HBFPY) ligand was studied in pure dimethylformamide (DMF), ethanol (EtOH), acetonitrile (AN) and in (DMF-EtOH), (AN-EtOH) and (DMF-AN) binary mixed solvent solutions at different temperatures using the conductometric method. Also in this work the complexation reaction between Ca²⁺, K⁺ cations and HBFPY ligand, was studied in pure dimethylformamide (DMF), propanol (PrOH), 1,4-dioxane (DOX), ethanol (EtOH) and in DMF-PrOH, DMF-DOX and DMF-EtOH binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between this ligand and the studied cations is 1 : 1 [ML]. In most cases, addition of HBFPY to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The stability constant of [Mg(HBFPY)]²⁺ complex in various neat solvents at 15°C decreases in order: EtOH > DMF > AN and the stability constant of [Ag(HBFPY)]⁺ complex in various neat solvents at 35°C decreases in order: DMF > EtOH. The values of standard enthalpy changes (ΔH° _c ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (ΔS° _c ) were calculated from the relationship ΔH° _c,295.15= ΔH° _c –298.15ΔS° _c .     

Synthesis and crystal structures of tetraacetylethylenediamine and <Emphasis Type="Italic">N</Emphasis>-(2-ammoniumethyl)carbamate

Two ethylenediamine derivatives—N-(2-ammoniumethyl)carbamate HN(COO^?)CH₂CH₂N⁺H₃ (I) and tetraacetylethylenediamine (H₃CC(O))₂NCH₂CH₂N(C(O)CH₃)₂ (II) (synthesized for the first time)—have been synthesized and characterized by X-ray crystallography. Compounds I and II are isolated as minor admixtures upon an attempt to synthesize ethylenediamine complexes of lanthanum and neodymium nitrates, respectively. The crystals of I and II are monoclinic: a = 7.778 Å, b = 8.060 Å, c = 7.568 Å, β = 95.73°, Z = 4, space group P2₁/c (I); a = 5.946, b = 10.255, c = 9.343 Å, β = 95.72°, Z = 2, space group P2₁/c (II). The bond lengths and bond angles lie within the corresponding standard values. Compounds I and II have different conformations of the N-C-C-N ethylenediamine moiety: gauche in I and trans in II, and the corresponding torsion angles are equal to 66.6° and 180°, respectively.     

New approaches to the calculation and interpretation of asymmetry factors of chromatographic peaks

The suitability of the determination of the asymmetry factor of chromatographic peaks by the ratio of areas of two components separated by a perpendicular dropped from the maximum of the peak to the base-line, A _s * = S _b /S _a , where symbol a corresponds to the leading edge of the peak and b is for its tailing slope, is discussed. It is demonstrated that this method enables the estimation of the asymmetry of even partially separated chromatographic signals, including those eluted “in the tail” of intense peaks of solvents. The concepts of the asymmetry index I(A _s *) and its increment ΔI(A _s *) = (A _s *)–I(A _s *) are introduced, which ensures the characterization of the asymmetry of peaks of polar analytes with respect to the asymmetry of nonpolar reference components, that is, the separation of the effects of the polarity of analytes and their quantities injected into the chromatographic column on this parameter. For the first time we revealed a correlation of the asymmetry factors of compounds of different chemical nature with such a characteristic of their polarity as the difference in chromatographic separation temperature and the normal boiling point of analytes.     

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.     

New mixed palladium—lead and palladium—tin tellurides of the NiAs type

New ternary mixed nickel arsenide-type palladium and platinum—Group 14 metal tellurides were searched for by the high-temperature ampoule synthesis combined with the X-ray powder diffraction analysis. As a result, new phases of the ternary Pd—Pb—Te and Pd—Sn—Te systems belonging to the NiAs structure type were synthesized. The crystal structure of the compound PdPb_0.304(5)Te_0.695(5) was determined by the Rietveld method (P6₃/mmc, a = 4.151(1) Å, c = 5.680(1) Å, Z = 2, R ₁ = 0.032, R _p = 0.075, wR _all = 0.025). It was shown that no ordering exists in the occupancy of the main-group atom site by lead and tellurium. In the Pd—Sn—Te system, a phase isostructural with the above-mentioned compound was found. In the latter phase, there is also no ordering in the occupancy of the main-group atom site. According to the electron diffraction data, a superstructure derived from the NiAs type exists in a narrow range of the compositions PdSn_0.3Te_0.7—PdSn_0.4Te_0.6.     

TXRF determination of mercury(II) in water in combination with liquid–liquid microextraction

A highly selective hybrid way of TXRF determination of mercury(II) in drinking water at the level of n(10^–2–10⁰) μg/L is developed. The technique of preconcentration of mercury(II) ions includes directly suspended droplet microextraction with benzene in the form of an iodide molecular complex. The proposed method of determination is characterized by its high degree of sensitivity and reproducibility (c _min = 8 ng/L, s _r = 0.12 (100 ng/L)). The accuracy of the analysis results is confirmed by the introduced–found method.     

Structure of the hexanuclear Cu(II) β-diketonate complex

The structure of the hexanuclear copper(II) β-diketonate complex with gfa (hexafluoroacetylacetone) and dpm (dipivalylmethanate) ligands was studied by low-temperature (T = 100 K) X-ray diffraction. Crystal data for Cu₆(gfa)₄(dpm)₄(OH)₄ [C₆₄H₈₄Cu₆F₂₄O₂₀]: a = 28.2364(7) Å, b = 12.8072(3) Å, c = 24.7199(7) Å, β= 115.900(1)°, V = 8041.5(4) ų, space group C2/m, Z = 4, d _calc 1.661 g/cm³. The coordination polyhedra of the copper atoms — squares and octahedra — are formed by the oxygen atoms of the gfa and dpm ligands and groups. In all cases, the Cu-O distances vary from 1.89 Å to 2.13 Å. The complexes follow the sites of the rhombohedral sublattice with the parameters a _c ≈ 14.4 Å and a _c ≈ 61.5°.     

Microwave spectrum,centrifugal perturbation,dipole moment,and conformation of 5-methyl-1,3-dioxane

The microwave spectrum of 5-methyl-1,3-dioxane was studied in the frequency range 12–35 GHz. The a and c type rotation transitions with J≤30 were identified. The rotational constants A = 4658.5244(33) MHz, B = 2383.3930(12) MHz, and C = 1724.28907(88) MHz and the quartic constants of the centrifugal distortion of the molecule in the ground vibrational state were determined. The components of the dipole moment were found, μ _a = 1.76 ± 0.01 D and μ _c = 1.10 ± 0.01 D; the net dipole moment of the molecule is μ = 2.08 ± 0.01 D. 5-Methyl-1,3-dioxane was calculated by the B3PW91/aug-cc-pVDZ density functional theory method. The calculated data are compared with the experimental data. The most stable conformation is the chair conformation with an equatorial orientation of the methyl group.     

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.     

New linear driving force correlation spanning long and short cycle time pressure swing adsorption processes

A simple, semi-empirical, generalized expression was developed for the LDF mass transfer coefficient k as a function of the half cycle time θ _c that encompasses and transitions between the well-known regions governed by the long cycle time constant Glueckauf k and the short cycle time dependent k. This new expression can be used to estimate k = f(θ _c ) for any system, irrespective of the loading and irrespective of θ _c , no matter if k is in the cycle time dependent region or not. A three times wider transition region between the Glueckauf k and the cycle time dependent k was also established, with the Glueckauf LDF limit now valid for θ _c  > 0.3 and the short cycle time limit now valid for θ _c  < 0.01. When evaluating this region for several adsorbate-adsorbent systems, the minimum Glueckauf θ _c spanned three orders of magnitude from thousands of seconds to just a few seconds, indicating a cycle time dependent k is not necessarily limited to what is normally considered a short cycle time. For virtually any θ _c less than this minimum Glueckauf θ _c , this new first-of-its-kind expression can be used to readily provide an accurate value of k = f(θ _c ). Since the widely accepted half cycle time concept does not apply to the actual simulation of a multi-step, unequal step time, pressure swing adsorption process, the value of k = f(θ _c ) from this new expression can be based on either the shortest cycle step in the cycle or a different value of k = f(θ _c ) for each cycle step time in the cycle, with validity confirmed either by experiment or by process simulation using the exact solution to the pore diffusion equation.     

Method validation parameters for drugs and explosives in ambient pressure ion mobility spectrometry

An approach using method validation (MV) parameters, otherwise known as analytical figures of merit was combined with electrospray ionization high performance ion mobility spectrometry (ESI-HPIMS) to describe an approach for evaluating drugs and explosives analysis in the field. MV parameters such as reduced mobility (K _o ), conditional reduced mobility (K _c ), resolving power (R _p ), theoretical plates (N), linearity, accuracy, precision, limit of detection (LOD), limit of quantitation (LOQ), repeatability, range, and reporting limit were investigated and developed for eleven drugs and six explosives. Our investigation estimated resolving power at 66 ± 0.64 for the ESI-HPIMS used. The LOD’s calculated ranged from 0.45–2.97 ng of material electrosprayed into the ESI-HPIMS. The LOQ’s calculated falls in the range 4.11–8.63 ng of material electrosprayed into the ESI-HPIMS. The key findings from this investigation were the following: K _c proves to be a measure of the identity of an explosive or drug ion; a parameter that may be applied to help aid IMS devices when detecting drugs and explosives. MV parameters, especially, K _c , introduced in this study is an effective parameter for establishing a unique identity of a drug or explosive. A control chart is an effective way to monitor the performance of an instrument and may be a useful tool for establishing reliability of confirmatory data in forensic investigations. MV parameters may be a reliable, accurate and unique identification marker for target drugs and explosives capable of differentiating these substances from false positive responses.     

Unexpected reactions of dichloro(ethyl)silane with DMSO in organic solvents

The effect of the solvent nature on the composition of the products formed upon the reaction between EtSi(H)Cl₂ and DMSO (molar ratio 1: 1, 0 °C) was revealed. This reaction in non-polar and low polar solvents (toluene, chloroform) gives oligoethyl(hydro)cyclo-siloxanes ((EtSi(H)O) _n , n = 3—8) as the major products in the yields up to 77%. In MeCN, oligoethyl(hydro)cyclosiloxanes are formed along with cyclic monochlorinated siloxanes ((EtSi(H)O) _n (EtSi(Cl)O), n = 2—7) in a ratio of ~7: 3 (68: 29 wt.%). In excess diethyl ether, the overall yield of oligoethyl(hydro)cyclosiloxanes does not exceed 25% and the major products are linear α,ω-diethoxyoligoethyl(hydro)siloxanes (EtO(EtSi(H)O) _n Et, n = 2—7) formed in 70—75% yields. A plausible reaction mechanism leading to the final products was suggested. Apparently, the reaction proceeds via ethyl(hydro)-and chloro(ethyl)silanones as intermediates.     

Synthesis,crystal, and molecular structure of coordination polymers constructed by self-assembly of NiN<Subscript>4</Subscript> cores with 2,2′-iminodibenzoate and nitroprusside ions

Two coordination compounds of compositions [Ni(L¹)(idba)(H₂O)]·1.5 H₂O (1) and [Ni(L²)Fe(CN)₅NO]·C₂H₅OH (2) where L¹ is N, N′-bis(3-aminopropyl)ethylenediamine, L² is 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene, and idba^2? is 2,2′-iminodibenzoate have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2₁/n (No. 14) with a=9.810(2) Å, b=10.230(2) Å, c=25.350(5) Å, V=2543.6(9) Å³, Z=4, and R=0.0727. The nickel atom is six-coordinated by four N atoms of amine and two O atoms of water and idba^2?. The molecular packing of the complex comprises of an infinite one-dimensional layered network in which the molecules in the crystal are held together by a system of hydrogen bonding. Complex 2, however, crystallizes in the space group C2/c (No. 15) of the monoclinic system with a=19.7990(4) Å, b=14.9440(3) Å, c=19.8800(3) Å, V=5115.90(17) Å³, Z=4, and R=0.0540. The Ni ion in compound 2 has a slightly distorted octahedral arrangement of the N₄ donor atoms of primary ligand L² and two N-donor atoms of the secondary nitroprusside ligand. The structure of 2 displays an extended one-dimensional network formed by linear [—Ni—NC—Fe—CN—] units. A cyclic voltammetric study shows that compound 1 undergoes a quasireversible oxidation attributable to Ni²⁺ → Ni³⁺ in the range 300–420 mV vs SCE.     

Analysis of Novel Antioxidant Sesquarterpenes (C<Subscript>35</Subscript> Terpenes) Produced in Recombinant <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Novel synthetic isoprenoids have been synthesized in engineered microbial hosts by evolving terpene synthase or expressing heterologous terpene synthases. Recently, the native operon, crtN_aN_cM derived from Planococcus sp. PAMC 21323, has isolated for potential industrial applications of C₃₅ carotenoids. For the first time, novel C₃₅ carotenoids (sesquarterpene) were synthesized in Corynebacterium glutamicum expressing the crtN_aN_cM genes. The recombinant strains accumulate various sesquarterpene including 4-apolycopene (red color), 4-aponeurosporene (yellow color), and no pigmentation, depending on the expression of the genetic elements of the crtN_aN_cM genes. Subsequently, the carotenoid extract from the cells harboring pCES-H36-CrtN_aN_cM was analyzed, resulting in significantly higher antioxidant activity than those of other strains harboring pCES-H36-CrtN_cM and pCES-H36-CrtN_aN_c, respectively. This study will promote further engineering of C. glutamicum to increase sesquarterpene productions.     

Structure and thermal properties of a novel volatile bis(1,1,1-trifluoro-5,5-dimethyl-3-hexene-4-imino-2-onate) platinum(II) compound

A novel volatile Pt(II)β-iminoketonate complex is synthesized. β-Aminovinylketone H(i-ptac) = [CF₃–C(O)–CH=C(NH₂)–C(CH₃)₃] is used as a ligand. The XRD method is used to determine the structures of the ligand and the complex. The crystallographic data for C₁₆H₂₂F₆N₂O₂Pt are as follows: a = 10.0716(4) Å, b = 10.9572(4) Å, c = 9.6322(4) Å, β = 110.9010(10)°, space group С2/m, Z = 2, R = 0.011. The platinum atom has a square planar coordination with two oxygen and two nitrogen atoms of two bidentately linked ketoiminate ligands in trans-position; the PtO₂N₂ coordination site is formed.     

Micromechanism of Cu and Fe alloying process on the martensitic phase transformation of NiTi-based alloys: First-principles calculation

Using first-principles pseudo-potential plane wave method, the formation enthalpy ΔH, binding energy ΔE, elastic constants, and electronic structure were calculated and analyzed carefully for NiTiX (X = Cu, Fe) shape memory alloy. The results show that the Cu or Fe element prefers to occupy the Ni site in the NiTi matrix phase respectively. Compared with the NiTi matrix phase, the ΔH, ΔE, c ₄₄ and c′ of NiTi (Cu) are similar to each other. However, the structural stability of the NiTi phase is improved obviously by the Fe alloying process. Simultaneously, the shear modulus c ₄₄ and c′ of NiTi (Fe) are larger than those of the NiTi matrix phase. Furthermore, Milliken population results indicate that Q _Cu–Ti is smaller than Q _Ni–Ti after the Cu alloying process, but Q _Fe–Ti is larger than Q _Ni–Ti. The electron density difference shows that some covalent bonding exists between Fe and Ti elements. Based on the upward analysis, the difference in the phase stability and elastic constants of NiTiX (X = Cu, Fe) is the substantial mechanism for the different M _s of NiTiX (X = Cu, Fe) although Cu or Fe substitutes for the same atom Ni elements in the NiTi matrix phase.     

Thermodynamic Parameters of the Dissolution of 4-Hydroxy-L-Proline and L-Phenylalanine in Mixed Aqueous Solvents at 298 K

The enthalpies of solution of 4-hydroxy-L-proline and L-phenylalanine in binary mixed aqueous solvents containing acetonitrile (AN), 1,4-dioxane (1,4-DO), or acetone (AC) at mole fractions of 0 to 0.25 are determined at T = 298.15 K via isothermal calorimetry. The standard enthalpies of solution (Δ_solH°) and transfer (Δ_trH°) of 4-hydroxy-L-proline and L-phenylalanine from water to mixed aqueous solvents are calculated using the experimental calorimetric data, as are the enthalpy coefficients of paired interactions (h _xy ) between the molecules of the investigated amino acids and the organic solvents. The effects the mixed aqueous solvent composition and the structure of the organic solvent molecules have on the enthalpies of solution and transfer for the investigated amino acids are considered. The correlation between the enthalpy of solution of the amino acids and the electron-donating properties of the organic solvents in the mixed aqueous solvent systems is established.     

Thermodynamics of the terpolymer of carbon monoxide,ethylene, and 1-butene

The heat capacity and the temperatures and enthalpies of physical transformations of the alternating terpolymer of carbon monoxide, ethylene, and 1-butene (the content of butene units is 10.7 mol.%) were studied by adiabatic and differential scanning calorimetry in the temperature range from 6 to 520 K. The energy of terpolymer combustion was measured at 298.15 K on an calorimeter with an isothermal shell and static bomb. The standard thermodynamic functions C°_p(T), H°(T)–H°(0), S°(T)–S°(0), and G°(T)–H°(0) for the range from Т → 0 to 400 K, the standard enthalpy of combustion, and the thermodynamic parameters of formation of the partially crystalline CO—ethylene—1-butene terpolymer at 298.15 K, as well as the thermodynamic characteristics of its synthesis in the range from T → 0 to 400 K were calculated.     

The enthalpies of solution of L-α-alanyl-L-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (T = 298.15 K) of L-α-alanyl-L-α-alanine in aqueous-organic solvents (acetonitrile, 1,4-dioxane, acetone, formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, and N,N-dimethylsulfoxide) were measured at organic component concentrations x ₂ = 0–0.3 mole fractions. The standard enthalpies of solution (Δ_sol H ^o) and transfer (Δ_tr H ^o) of the peptide from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics is considered. The enthalpy pair interaction coefficients h _xy between L-α-alanyl-L-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft four-parameter equation was used to reveal correlation between the h _xy values and the properties of organic solvents.     

Solubility and Solution Thermodynamic Properties of 4-(4-Hydroxyphenyl)-2-butanone (Raspberry Ketone) in Different Pure Solvents

The solubility of 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone) in six pure solvents was experimentally determined at temperatures ranging from 283.15 to 313.15 K under the pressure 0.10 MPa by employing a gravimetrical method. The experimental results indicate that the solubility of raspberry ketone in all studied solvents is temperature dependent, a rise in temperature brings about an increase in solubility. The experimental solubility data of raspberry ketone in six pure solvents (acetone, ethanol, ethyl acetate, n-propyl alcohol, n-butyl alcohol, and distilled water) was correlated by using several commonly used thermodynamic models, including the Apelblat, van’t Hoff and λh equations. The results of the error analysis indicate that the van’t Hoff equation was able to give more accurate and reliable predictions of solubility with root-mean-square deviation less than 0.56%. Furthermore, the changes of dissolution enthalpies (Δ_diss H°), dissolution entropies (Δ_diss S°) and dissolution Gibbs energies (Δ_diss G°) of raspberry ketone in the solvents studied were estimated by the van’t Hoff equation. The positive value of Δ_diss H°, Δ_diss S°, and Δ_diss G° indicated that these dissolution processes of raspberry ketone in the solvents studied were all endothermic and enthalpy-driven.