Physical properties of 3-methyl-N-butylpyridinium tetracyanoborate and 1-butyl-1-methylpyrrolidinium tetracyanoborate and ternary LLE data of [3-mebupy]B(CN)4 with an aromatic and an aliphatic hydrocarbon at T = 303.2 K and 328.2 K and p = 0.1 MPa

Several physical properties were determined for the ionic liquids 3-methyl-N-butylpyridinium tetracyanoborate ([3-mebupy]B(CN)₄) and 1-butyl-1-methylpyrrolidinium tetracyanoborate ([1-mebupyr]B(CN)₄), viz. liquid density, viscosity, surface tension, thermal stability, and heat capacity over the temperature range from 283.2 K to 475.2 K and at 0.1 MPa. The density and the surface tension were well correlated with linear equations and the viscosity with a Vogel–Fulcher–Tamman equation. The IL [3-mebupy]B(CN)₄ is stable up to a temperature of 480 K and the IL [1-mebupyr]B(CN)₄ up to a temperature of 548 K.Ternary data for the systems {(benzene + n-hexane), or (toluene + n-heptane), or (p-xylene + n-octane + [3-mebupy]B(CN)₄)} were determined at T = 303.2 K and 328.2 K and p = 0.1 MPa. All experimental data were well correlated with the NRTL model. The values of the experimental and calculated aromatic/aliphatic selectivity are in good agreement with each other. The LLE data of [1-mebupyr]B(CN)₄ were only measured in a 10 vol% aromatic feed for the three systems.     

Studies on some ternary complexes of copper(II) involving an amino penicillin drug

Multiple equilibrium studies by pH-metric measurements in the ternary copper(II) complexes with ampicillin(amp) as ligand A and glycine(gly), dl-2-aminobutanoic acid(2aba), dl-3-aminobutanoic acid(3aba), 1,2-diaminopropane(dp), 1,3-diaminopropane(tp), dl-2,3-diaminopropanoic acid(dapa), dl-2,4-diaminobutanoic acid(daba) & dl-2,5-diaminopentanoic acid(ornithine)(orn) as ligands B show the presence of CuABH, CuAB or CuAH?1 B ternary complex species. In the CuAB species the binding of the ligands A and B is similar to their binding in their respective binary complexes. In CuABH_?1 species the deprotonation occurs with amp(A) ligand. The Δlog K values indicate higher stabilities for the ternary complexes than the binary species. The CuAB species with B = gly, 2aba, dapa & orn have been isolated and characterized. The conductivity measurements indicate that the complexes are non-electrolytes. Magnetic susceptibility and electronic spectral data suggest a square pyramidal geometry for CuAB with B = gly/2aba complexes and distorted octahedral geometry for CuAB with B = dapa/orn. The vibrational spectra are interpreted to find the mode of binding of ligand to metal. The TG/DTA studies reveal that the complexes decompose in three steps, indicating non-involvement of hydrated or coordinated water molecules in the complex. The cyclic voltammograms indicate a quasi reversible Cu²⁺/Cu⁺ couple. The antimicrobial activity and CT-DNA cleavage ability of the complexes show higher activity for ternary complexes.     

Combined experimental and computational study on the energetics of 1,2-benzisothiazol-3(2H)-one and 1,4-benzothiazin-3(2H, 4H)-one

The present work reports an experimental and computational study of the energetics of 1,2-benzisothiazol-3(2H)-one and 1,4-benzothiazin-3(2H, 4H)-one. The standard (p° = 0.1 MPa) massic energy of combustion, at T = 298.15 K, of each compound was measured by rotating bomb combustion calorimetry, in oxygen that allowed the calculation of the respective standard molar enthalpy of formation, in the condensed phase, at T = 298.15 K. The standard molar enthalpies of sublimation, at T = 298.15 K, were measured by high-temperature Calvet microcalorimetry. From the combination of data obtained by both techniques we have calculated the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K. In addition, computational calculations were carried using the density functional theory with the B3LYP functional and the 6-31G1 basis set and some correlations between structure and energetics were obtained for the keto and enol forms of both compounds. Using the G3(MP2)//B3LYP composite method and various appropriate reactions, the standard molar enthalpies of formation of 1,2-benzisothiazol-3(2H)-one and 1,4-benzothiazin-3(2H, 4H)-one, at T = 298.15 K, were computationally derived and compared with the experimental data. The aromaticity of 1,2-benzisothiazol-3(2H)-one, 1,4-benzothiazin-3(2H, 4H)-one and that of some related species was evaluated by analysis of nucleus independent chemical shifts (NICS).     

Two new saponins from Anemarrhena asphodeloides Bge.

Two new saponins 3-O-β-D-glucopyranosyl (1→2)-β-D-mannopyranosyl sarsasapogenin, named timosaponin A IV(1) and (5β, 25S)-26-O-β-D-glucopyranosyl-furost-20(22)-en-3,26-diol-3-O-β-D-glucopyranosyl (1→4) glucopyranosyl (1→2)-β-D-galacopyranoside, named timosaponin B IV(2), were isolated by silica gel column chromatography and preparative HPLC from Anemarrhena asphodeloides Bge. Their structures were elucidated by chemical characters and spectroscopic analysis.     

A study of the conformational stability and the vibrational spectra of 2,3-dichloro-1-propanol

The conformational stability and the three rotor internal rotations in 2,3-dichloro-1-propanol were investigated at DFT-B3LYP/6-311 + G**, MP2/6-311 + G** and MP4(SDQ) levels of theory. From the calculated potential energy surface, ten distinct minima were located all of which were predicted to have real frequencies at the B3LYP level of theory. The calculated lowest energy minima in the potential curves of the molecule were predicted to correspond to the Ggg and Gtg1 structures. The observed broad and very intense infrared band centered at about 3370 cm^?1 supports the existence of the strong intermolecular H-bonding in 2,3-dichloro-1-propanol. The equilibrium constants for the conformational interconversion in the molecule were estimated from the calculated Gibb's energies at the B3LYP/6-311 + G** level of calculation and found to correspond to an equilibrium mixture of about 49% Ggg, 27% Gtg1, 5% Ggt and 5% Tgg conformations at 298.15 K.     

Thermodynamics of binary and ternary interactions in the tin(II)/phytate system in aqueous solutions,in the presence of Cl− or F−

An extensive study of the tin(II)/phytate (Phy) system was carried out in NaNO_3(aq), at different ionic strengths (0.10 ⩽ I/mol · L⁻¹ ⩽ 1.00) and temperatures (278.15 ⩽ T/K ⩽ 328.15), by potentiometric and voltammetric techniques. The stability and formation enthalpy changes of six SnH_qPhy species were determined. To better characterise this system, some potentiometric titrations were also carried out in mixed ionic media (NaNO_3(aq) + NaCl_(aq) and NaNO_3(aq) + NaF_(aq)) at total ionic strength I = 1.00 mol · L⁻¹. The formation of some ternary mixed SnH_qPhyCl and SnH_qPhyF species (charges omitted for simplicity) was found. The formation enthalpies of the complex species were calculated, at I = 0.40 mol · L⁻¹ in NaNO_3(aq), by the dependence of stability constants on temperature obtained by potentiometric titrations, in the range 278.15 ⩽ T/K ⩽ 328.15. The complex formation process is endothermic, and the main contribution to tin(II) complexation by phytate is entropic in nature. For example, for the SnPhy species we have, at T = 298.15 K and I = 0.40 mol · L⁻¹ in NaNO_3(aq): ΔH = 57.7 ± 2.8 kJ mol · L⁻¹, ΔG = −99.9 ± 1.7 kJ mol · L⁻¹, and TΔS = 158 ± 3 kJ mol · L⁻¹. The ionic strength dependence of the formation constants of the simple tin(II)/phytate species, was modelled by the Debye–Hückel and the SIT approaches. The sequestering ability of phytate towards tin(II) was evaluated by calculating the pL_0.5 values (i.e., the total ligand concentration necessary to bind 50% of cation present in trace) at different ionic strengths, ionic media, and pH. The sequestering ability increases with increasing the pH, whilst it decreases with increasing the ionic strength (the same behaviour shown by the stability constants). Moreover, taking into account the different sequestering ability of phytate towards tin(II) in the different ionic media, the trend: pL_0.5 = 5.70 (in NaNO_3(aq) + NaF_(aq)) > pL_0.5 = 5.16 (in NaNO_3(aq) + NaCl_(aq)) > pL_0.5 = 4.86 (in NaNO_3(aq)) was observed at pH 8.1 and I = 1.00 mol · L⁻¹. This is due to the presence of a second ligand (Cl⁻ or F⁻) that stabilizes the complex species with the formation of ternary complex species. Some empirical relationships were also found.     

Energetic effects of ether and ketone functional groups in 9,10-dihydroanthracene compound

The energetic effects caused by replacing one of the methylene groups in the 9,10-dihydroanthracene by ether or ketone functional groups yielding xanthene and anthrone species, respectively, were determined from direct comparison of the standard (p° = 0.1 MPa) molar enthalpies of formation in the gaseous phase, at T = 298.15 K, of these compounds. The experimental static-bomb combustion calorimetry and Calvet microcalorimetry and the computational G3(MP2)//B3LYP method were used to get the standard molar gas-phase enthalpies of formation of xanthene, (41.8 ± 3.5) kJ · mol^?1, and anthrone, (31.4 ± 3.2) kJ · mol^?1. The enthalpic increments for the substitution of methylene by ether and ketone in the parent polycyclic compound (9,10-dihydroanthracene) are ?(117.9 ± 5.5) kJ · mol^?1 and ?(128.3 ± 5.4) kJ · mol^?1, respectively.     

Chemical composition and antioxidant, α-glucosidase inhibitory and antibacterial activities of three Echeveria DC. species from Mexico

Three Echeveria species from Sinaloa, Mexico (Echeveria craigiana, Echeveria kimnachii and Echeveria subrigida) were analyzed for their content of antioxidant compounds (β-carotene, ascorbic acid, α-tocopherol, total phenolics and flavonoids) and the in vitro antioxidant (DPPH, ABTS, ORAC and β-carotene bleaching [β-CBM]), α-glucosidase inhibitory and antibacterial activities. The studied Echeveria species showed high α-tocopherol content (2.9–9.0 mg/100 g f.w.) and total phenolics as Gallic Acid Equivalents (GAE) (152.2–400.5 mg GAE/100 g f.w.). Antioxidant activities of the three Echeveria methanol extracts (ME) were higher than those of other well-known plants with this property; the activities of E. craigiana (ABTS, 65.91 μmol ET/g f.w.) and E. subrigida (β-CBM, 79.3%) were remarkable. The Echeveria ME showed stronger α-glucosidase inhibition (IC₅₀ 25.21–50.57 μg/mL) than acarbose (IC₅₀ 3.59 mg/mL) as well as high antibacterial activity (Minimal Inhibitory Concentrations, MICs ⩽ 1 mg/mL), mainly against Gram positive bacteria. The results showed the three Echeveria species had components/biological activities with high potential for food/pharmacological uses and could be exploited by sustainable management schemes.     

Phase transitions on (liquid + liquid) equilibria for (water + 1-methylnaphthalene + light aromatic hydrocarbon) ternary systems at T = (563, 573, and 583) K

Phase transitions for (water + 1-methylnaphthalene + light aromatic hydrocarbon) ternary systems are observed at their (liquid + liquid) equilibria at T = (563, 573, and 583) K and (8.6 to 25.0) MPa. The phase transition pressures at T = (563, 573, and 583) K were measured for the five species of light aromatic hydrocarbons, o-, m-, p-xylenes, ethylbenzene, and mesitylene. The measurements of the phase transition pressures were carried out by changing the feed mole fraction of water and 1-methylnaphthalene in water free, respectively. Effects of the feed mole fraction of water on the phase transition pressures are very small. Increasing the feed mole fraction of 1-methylnaphthalene results in decreasing the phase transition pressures at constant temperature. The slopes depending on the feed mole fraction for 1-methylnaphthalene at the phase transition pressures are decreased with increasing temperature for (water + 1-methylnaphthalene + p-xylene), (water + 1-methylnaphthalene + o-xylene), and (water + 1-methylnaphthalene + mesitylene) systems. For xylene isomers, the highest and lowest of the phase transition pressures are obtained in the case of p- and o-xylenes, respectively. The phase transition pressures for ethylbenzene are lower than those in the case of p-xylene. The similar phase transition pressures are given for p-xylene and mesitylene.     

A DFT study on group III and V combined hexagonal clusters as potential building motifs for inorganic nanomaterials

A detail theoretical investigation on the structure and electronic properties of inorganic hexagonal units and their higher order derivatives comprising group III (B, Al and Ga) and V (N, P and As) elements is performed. A series of 45 clusters, formed by a linear combination of hydrogen saturated hexagonal motifs up to five units, (MY)_2n+1H_2n+4 (M = B, Al, Ga; Y = N, P, As; n = 1–5) are considered to look into their metal–insulator–semiconductor (MIS) behavior. It is evident from the present study that the arsenic doped group III hexagonal units clearly have a decisive role in forming semiconductor materials.     

Fluoride affinities of fluorinated alanes

The fluoride affinities of fluorinated alanes, AlH_mF_3?m (m = 1–3) were measured using energy-resolved collision-induced dissociation of fluorinated aluminate anions. The AlH_mF_4?m^? anions were formed by reaction of dimethylethylamine-alane with fluoride ion and F₂. From the measured bond dissociation energies, the fluoride affinities of fluorinated alanes are determined to be 93.2 ± 3.1, 97.5 ± 4.0, and 108.6 ± 3.7 kcal/mol for m = 3, 2, and 1, respectively. The fluoride affinities are in good agreement with the theoretical calculations at the CCSD(T)/CBS and B3LYP/6-31 + G* levels of theory. The increased Lewis acidity of more fluorinated alanes is attributed to increased positive charge density on the aluminum.     

The experimental and DFT studies of 1,3-dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide

1,3-Dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide (1) was synthesized and characterized by X-ray diffraction, ¹H NMR, MS, IR, UV–vis spectra and elemental analysis. The crystals are monoclinic, space group P2₁/c, with a = 12.507(3) Å, b = 7.3259(19) Å, c = 36.705(9) Å, V = 3358.9(15) Å³, and Z = 4 (at 296(2) K). Crystal stacking scheme indicates the face-to-face π?π aromatic stacking interactions. Molecular geometries, frequencies, IR, ¹H NMR and UV–vis were calculated at DFT/TD-DFT level using two hybrid exchange–correlation functionals, B3LYP and PBE1PBE. The stability of the molecule arising from hyperconjugative interaction and charge delocalization had been analyzed using natural bond orbital (NBO) analysis. These calculations on (1) provide deep insight into its electronic structure and properties.     

An oxazoline derivatized Pybox ligand for Eu(III) and Tb(III) sensitization

A new Tb(III) dimer with an oxazoline-derivatized pyridine ligand, dimethyl-2,2′-(pyridine-2,6-diyl)bis(4,5-dihydrooxazole-4-carboxylate), has been isolated. This complex is highly luminescent and crystallizes in the triclinic P-1 space group with parameters a = 9.6167(2) Å, b = 11.6786(2) Å, c = 12.7548(3) Å, α = 70.026(1)°, β = 83.219(1)°, γ = 81.973(1)° and V = 1329.31(51)ų. Solution speciation studies showed the formation of monomeric species with 1:1 and 2:1 ligand-to-metal ion stoichiometries with log β₁₁ = 3.66 ± 0.41 and log β₂₁ = 6.16 ± 0.37 for Eu(III) and log β₁₁ = 3.56 ± 0.41 and log β₂₁ = 6.21 ± 0.38 for Tb(III). The quantum yields of emission Φ and luminescence lifetimes τ of solutions with 2:1 stoichiometry were 26.4 ± 0.5% and 1.47 ± 0.06 ms for Eu(III) and 41.0 ± 1.3% and 1.87 ± 0.06 ms for Tb(III).     

Standard molar enthalpy of formation of 1-benzosuberone: An experimental and computational study

The energetics of 1-benzosuberone was studied by a combination of calorimetric techniques and computational calculations.The standard (p° = 0.1 MPa) molar enthalpy of formation of 1-benzosuberone, in the liquid phase, was derived from the massic energy of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The standard molar enthalpy of vaporization, at T = 298.15 K, was measured by Calvet microcalorimetry. From these two parameters the standard (p° = 0.1 MPa) molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived: ?(96.1 ± 3.4) kJ · mol^?1. The G3(MP2)//B3LYP composite method and appropriate reactions were used to computationally calculate the standard molar enthalpy of formation of 1-benzosuberone, in the gaseous phase, at T = 298.15 K. The computational results are in very good agreement with the experimental value.     

Selective determination of inorganic cobalt in nutritional supplements by ultrasound-assisted temperature-controlled ionic liquid dispersive liquid phase microextraction and electrothermal atomic absorption spectrometry

In the present work, a simple and rapid analytical method based on application of ionic liquids (ILs) for inorganic Co(II) species (iCo) microextraction in a variety of nutrient supplements was developed. Inorganic Co was initially chelated with 1-nitroso-2-naphtol (1N2N) reagent followed by a modern technique named ultrasound-assisted temperature-controlled ionic liquid dispersive liquid phase microextraction (USA-TILDLME). The extraction was performed with 1-hexyl-3-methylimidazolium hexafluorophosphate [C₆mim][PF₆] with the aid of ultrasound to improve iCo recovery. Finally, the iCo-enriched IL phase was solubilized in methanol and directly injected into an electrothermal atomic absorption spectrometer (ETAAS). Several parameters that could influence iCo microextraction and detection were carefully studied. Since the main difficulty in these samples is caused by high concentrations of potential interfering ions, different approaches were evaluated to eliminate interferences. The limit of detection (LOD) was 5.4 ng L^?1, while the relative standard deviation (RSD) was 4.7% (at 0.5 μg L^?1 Co level and n = 10), calculated from the peak height of absorbance signals. Selective microextraction of iCo species was achieved only by controlling the pH value during the procedure. The method was thus successfully applied for determination of iCo species in nutritional supplements.     

Superhalogens as building blocks of complex hydrides for hydrogen storage

Superhalogens are species whose electron affinity (EA) or vertical detachment energy (VDE) exceeds those of halogens. These species typically consist of a central electropositive atom with electronegative ligands. The EA or VDE of species can be further increased by using superhalogens as ligands, which are termed as hyperhalogens. Having established BH₄⁻ as a superhalogen, we have studied BH_4 − x(BH₄)_x⁻ (x = 1–4) hyperhalogen anions and their Li-complexes LiBH_4 − x(BH₄)_x using density functional theory. The VDE of these anions is larger than that of BH₄⁻, which increases with the increase in number of peripheral BH₄ moieties (x). The hydrogen storage capacity of LiBH_4 − x(BH₄)_x complexes is higher but binding energy is smaller than that of LiBH₄, a typical complex hydride. The linear correlation between the dehydrogenation energy of LiBH_4 − x(BH₄)_x complexes and the VDE of BH_4 − x(BH₄)_x⁻ anions is established. These complexes are found to be thermodynamically stable against dissociation into LiBH₄ and borane. This study demonstrates the role of superhalogens in designing new materials for hydrogen storage and should also motivate experimentalists to synthesize LiBH_4 − x(BH₄)_x (x = 1–4) complexes.     

Supramolecular fluoride and chloride anions

The Cambridge Structural Database has been searched for supramolecular anions of the form H_nX_n + 1⁻ where X is fluorine (n = 1 to 6) and chlorine (n = 1 to 5); no credible evidence was found for comparable bromine or iodine species. Several structural isomers have been identified, and an experimental measure has been developed which seems to distinguish between two-centre and three-centre bonded species. There are also examples of suprafluoride and suprachloride anions as ligands in organometallic complexes. Most of these anions have not been previously described.     

Thermodynamic analysis of sorption isotherms of chromium(VI) anionic species on reed biomass

A new sorbent material for removing Cr(VI) anionic species from aqueous solutions has been investigated. Adsorption equilibrium and thermodynamics of Cr(VI) anionic species onto reed biomass were studied at different initial concentrations, sorbent concentrations, pH levels, temperatures, and ionic strength. Equilibrium isotherm was analyzed by Langmuir model. The experimental sorption data fit the model very well. The maximum sorption capacity of Cr(VI) onto reed biomass was found to be 33 mg · g^?1. It was noted that the Cr(VI) adsorption by reed biomass decreased with increase in pH. An increase in temperature resulted in a higher Cr(VI) loading per unit weight of the adsorbent. Removal of Cr(VI) by reed biomass seems to be mainly by chemisorption. The change in entropy (ΔS^°) and heat of adsorption (ΔH^°) for Cr(VI) adsorption on reed biomass were estimated as 2205 kJ · kg^?1 · K^?1 and 822 kJ · kg^?1, respectively. The values of isosteric heat of adsorption varied with the surface loading of Cr(VI).