Bonding interactions in oxydiacetate and thiodiacetate cobalt(II) and nickel(II) complexes

The influence of the central donor atom of the oxydiacetate and thiodiacetate ligands (oxygen and sulphur atoms, respectively) on the thermodynamic parameters for complexation reactions of the Co²⁺ and Ni²⁺ ions has been investigated using the isothermal titration calorimetry (ITC) technique and density functional theory (DFT) computations. The polarized continuum (PCM) - solvation model was employed to describe the structural factors that govern the coordination modes of the ligands (mer or fac) in the solution. The differences in the binding enthalpies of the investigated complexes were discussed based on the results obtained both from the natural bond orbital (NBO) analysis and the second-order perturbation theory.     

2-Methylthio-imidazolins: a rare case of different tautomeric forms in solid state and in solution

Structural Chemistry - The synthesis and structure elucidation of two new compounds, 2-(methylthio)-1,3-diazaspiro[4.4]non-2-ene-4-one (1) and 2-(methylthio)-1,3-diazaspiro[4.4]non-2-ene-4-thione...     

Macro- and micro- elements in some herbal drug raw materials and their water extracts consumed in Poland

The concentrations of seven macro- and microelements (K, Mg, Ca, Na, Fe, Zn, Mn) in 59 herbs (herbs, leaves, flowers, fruits, roots), which are commercially available and frequently used in Poland for medical purposes as well as in their water extracts (infusions and decoctions), were determined after microwave mineralization. The data obtained show that all herbal raw materials analysed contain macroelements in the range of mg g⁻¹ on d.w. whereas microelements in the range of mg kg⁻¹ on d.w. and that elemental concentrations varied widely. On the basis of a comparison of concentrations of elements in herbal raw materials examined and water extracts prepared from them, the extraction efficiency was expressed as a percent of the total content of each element present in the infusion or decoction. The percentages of macro- and micro- elements leaching from different morphological parts of plants into water extracts varied across a wide range of values, from 1% in the case of Na to 56% in the case of K. Real daily intake of the macro- and microelements elements through one cup of infusions or decoctions were shown that water extracts from herbal raw materials are not an important source of bioelements in human diet.      

Electrochemical characterization of Prussian blue type nickel hexacyanoferrate redox mediator for potential application as charge relay in dye-sensitized solar cells

A polynuclear electronically/ionically (redox) conducting mixed-valent inorganic material such as nickel(II) hexacyanoferrate(II,III), NiHCF, was considered for potential application as a redox mediator (charge relay) in dye-sensitized solar cell (DSSC). The NiHCF redox reactions were found fast and reversible not only when the system was studied as thin film exposed to an aqueous supporting electrolyte but also as bulk material (pasted powder) in solid state, i.e., in the absence of contact with external liquid electrolyte phase. Usefulness of NiHCF material was diagnosed using conventional electroanalytical approaches, solid-state voltammetric methodology, as well as the dynamic electrochemical impedance spectroscopy technique that permitted monitoring of impedance spectra under potentiodynamic conditions. The material was utilized in a mixed-valent state, i.e., as a mixture of K₄Ni^II[Fe^II(CN)₆] and K₃Ni^II[Fe^III(CN)₆] in which iron(II) and iron(III) sites were at the 1:1 ratio. Under such conditions, dynamics of electron-hopping between mixed-valent iron sites was maximized. Our DSSC utilized cis–dithiocyanoatobis(4,4′-dicarboxylic acid-2,2′-bipyridine) ruthenium(II) dye (N3) adsorbed onto TiO₂ semiconductor and NiHCF as redox mediator. Although performance of our DSSC was not optimized in terms of the NiHCF film thickness and morphology, as well as lower photocurrents in comparison to those characteristic of the iodine/iodide based DSSC were obtained, our system yielded readily fairly high open-circuit photovoltages on the level of 800 mV. An important issue was that the formal potential of NiHCF was more positive relative to the potential of the iodide/triiodide couple while being still more negative than that equivalent to the ground state of the N3 dye. Thus, NiHCF mediator was able to regenerate the dye.

     

1H and 13C NMR characteristics of β-blockers

The β-blockers are important drugs and decades of clinical experience proved their high medical status. However, to the best of our knowledge, there is no complete assignment of (1)H and (13)C NMR resonances of popular representatives: acebutolol, alpenolol, pindolol, timolol and propranolol and the published NMR data on carvedilol and atenolol are incorrect. Therefore, (1)H and (13)C NMR spectroscopy was applied for the characterization of a series of β-adrenolytics: carvedilol (1), pindolol (2), alprenolol (3), acebutolol (4), atenolol (5), propranolol (6) and timolol (7). Two-dimensional NMR experiments (COSY, HMQC, HMBC, NOESY) allowed the unequivocal assignment of (1)H and (13)C spectra for solution (DMSO-d(6) ). Salts and bases can be easily distinguished based on (13)C chemical shifts which are within 65.0-65.5 ppm (OC2) and 46.9-47.0 (NC3) for hydrochlorides and larger, ca. 68.4 ppm (OC2) and 50.3-52.6 (NC3) for bases. NMR data of 1-7 should be included in pharmacopoeias.     

Investigations on the interaction of dichloroaluminum carboxylates with Lewis bases and water: an efficient road toward oxo- and hydroxoaluminum carboxylate complexes

A series of dichloroaluminum carboxylates [Cl(2)Al(O(2)CR)](2) (were R = Ph (1a), (t)Bu (1b), CHCH(2) (1c) and C(11)H(23) (1d)) were prepared and extended investigations on their structure and reactivity toward various Lewis bases and H(2)O performed. Compounds [Cl(2)Al(O(2)CR)](2) and their adducts with Lewis bases show a large structural variety, featuring both molecular and ionic forms with different coordination numbers of the metal center and various coordination modes of the carboxylate ligand. Upon addition of a Lewis base of moderate strength the molecular form [Cl(2)Al(O(2)CR)](2) equilibrates with new ionic forms. In the presences of 4-methylpyridine the six-coordinate Lewis acid-base adducts [Cl(2)Al(λ(2)-O(2)CR)(py-Me)(2)] [R = Ph (3a), (t)Bu (3b)] with a chelating carboxylate ligand were formed. The reactions of 1a, 1b, and 1d with 0.33 equiv of H(2)O in THF-toluene solution lead to oxo carboxylates [(Al(3)O)(O(2)CR)(6)(THF)(3)] [AlCl(4)] [where R = Ph (4a(THF)), (t)Bu (4b(THF)), and C(11)H(23) (4d(THF))] in high yield. The similar reaction of 1c in tetrahydrofuran (THF) afforded the chloro(hydroxo)aluminum acrylate [(ClAl)(2)(OH)(O(2)CC(2)H(3))(2) (THF)(4)][AlCl(4)] (5), while the hydrolysis of 1b in MeCN lead to the hydroxoaluminum carboxylate [Al(2)(OH)(O(2)C(t)Bu)(2)(MeCN)(6)][AlCl(4))(3)] (6). All compounds were characterized by elemental analysis, (1)H, (27)Al NMR, and IR spectroscopy, and the molecular structure of 1a, 3a, 3b, 4a(THF), 4b(THF), 4b(py-Me'), 5, and 6 were determined by single-crystal X-ray diffraction. The study provides a platform for testing transformations of secondary building units in Al-Metal-Organic Frameworks toward H(2)O and neutral donor ligands.     

Vibrational spectroscopic characterization of the magnesium borate-phosphate mineral lüneburgite

ABSTRACT

Lüneburgite, a rare magnesium borate-phosphate mineral from Mejillones, Chile, has been characterized using Raman and mid-infrared spectroscopy methods. Boron tetrahedra are characterized by sharp Raman band at 877?cm^?1, attributed to the ν₁[BO₄]^5? symmetric stretching mode. The phosphate anion is associated with a distinct band at 1032?cm^?1, attributed to the ν₃[PO₄]^3? antisymmetric stretching mode. The most intensive Raman band at 734?cm^?1 is ascribed to stretching vibrations of bridging oxygen atoms in boron–oxygen–phosphor bridges. Bonds associated with water bending mode and stretching vibration are observed at 1661?cm^?1 (infrared) and in the 3000–3500?cm^?1 region (Raman and infrared spectrum).     

A study of the convergence of and error estimation for the homotopy perturbation method for the Volterra–Fredholm integral equations

In this work the solution of the Volterra–Fredholm integral equations of the second kind is presented. The proposed method is based on the homotopy perturbation method, which consists in constructing the series whose sum is the solution of the problem considered. The problem of the convergence of the series constructed is formulated and a proof of the formulation is given in the work. Additionally, the estimation of the approximate solution errors obtained by taking the partial sums of the series is elaborated on.     

Towards a new family of photoluminescent organozinc 8-hydroxyquinolinates with a high propensity to form noncovalent porous materials

We report on investigations of reactions of tBu(2)Zn with 8-hydroxyquinoline (q-H) and the influence of water on the composition and structure of the final product. A new synthetic approach to photoluminescent zinc complexes with quinolinate ligands was developed that allowed the isolation of a series of structurally diverse and novel alkylzinc 8-hydroxyquinolate complexes: the trinuclear alkylzinc aggregate [tBuZn(q)](3) (1(3)), the pentanuclear oxo cluster [(tBu)(3)Zn(5)(μ(4) -O)(q)(5)] (2), and the tetranuclear hydroxo cluster [Zn(q)(2)](2)[tBuZn(OH)](2) (3). All compounds were characterized in solution by (1)H NMR, IR, UV/Vis, and photoluminescence (PL) spectroscopy, and in the solid state by X-ray diffraction, TGA, and PL studies. Density functional theory calculations were also carried out for these new Zn(II) complexes to rationalize their luminescence behavior. A detailed analysis of the supramolecular structures of 2 and 3 shows that the unique shape of the corresponding single molecules leads to the formation of extended 3D networks with 1D open channels. Varying the stoichiometry, shape, and supramolecular structure of the resulting complexes leads to changes in their spectroscopic properties. The close-packed crystal structure of 1(3) shows a redshifted emission maximum in comparison to the porous crystal structure of 2 and the THF-solvated structure of 3.     

LC-MS/MS fast analysis of androgenic steroids in urine

The liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated to detect androgenic steroids: trenbolone, nortestosterone, boldenone, methylboldenone, testosterone, methyltestosterone, 17β-1-testosterone and their metabolites in bovine urine. Sample preparation before LC-MS/MS analysis involved an enzymatic hydrolysis with glucuronidase AS-HP, isolation of free hormones from urine on C(18) SPE column and purification of the extract using liquid-liquid extraction with n-pentane and SPE NH(2) column. For the chromatographic separation of steroids, the Poroshell 120-EC C18 column (150?×?2.1 mm, 2.7 μm) was used. Mass spectrometric measurement was achieved using the API 4000 triple quadrupole (QqQ) instrument with a TurboIon-Spray source operating in positive electrospray ionization mode. The procedure was validated according to the Decision 2002/657/EC. Recovery ranged from 76.5% to 118.9% for all examined compounds. The repeatability was below 20% and reproducibility did not exceed the 25%. The linearity was good for all analytes in the whole range of tested concentrations, as proved by the correlation coefficients greater than 0.99. The decision limit (CCα) ranged from 0.10 to 0.17 μg L(-1) for all analytes, whereas the detection capability (CCβ) ranged from 0.17 to 0.29 μg L(-1). The application of an innovative Poroshell column allowed for very good chromatographic separation of steroids with a much shorter time of analysis.