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.     

Identification of degradation products of indigoids by tandem mass spectrometry

The study concerns identification of photodegradation products of indigotin, indirubin and isoindigo. Experimental methodology consists of degradation of standard solutions of indigoids in a solar box and analysis of samples taken at different aging time by using capillary high‐performance liquid chromatography coupled with electrospray ionization tandem mass spectrometric and spectrophotometric detectors. Identification of the formed compounds was based on careful interpretation of the electrospray ionization MS/MS spectra. Apart from the well‐known degradation products of indigoids: isatin, isatoic anhydride and anthranilic acid, another seven species were also identified, and their proposed structures were confirmed by high‐resolution molecular masses measurements; according to the best knowledge of authors, they have not been reported so far. The obtained results formed the basis for postulating mechanism of the process. Moreover, the MRM (Multiple Reaction Monitoring) method was developed for the identification of natural dyes and their degradation products in textiles of historical value. Apart from such colorants as indigotin and flavonoids, also presence of degradation products of indigoids was confirmed. Copyright © 2015 John Wiley & Sons, Ltd.     

Physicochemical characteristics of 2-, 3- and 4-methylpyridinium tetrachloroferrates(III)

The crystal structure of 2-methylpyridinium tetrachloroferrate(III) was determined. The iron cation is tetracoordinated by chloride anions, and it adopts a slightly distorted tetrahedral coordination with three angles smaller, two almost equal and one larger than the tetrahedral. The compound is isostructural with its 3-, and 4-methylpyridinium analogues. The thermal properties of 2-, 3- and 4-methylpyridinium tetrachloroferrates(III) have been studied using TG and DSC techniques. The compounds exhibit a high stability in the melt.      

Ligand binding intermediates of nitrosylated human hemoglobin induced at low temperature by X-ray irradiation

Under prolonged X-ray irradiation, the ferrous heme of nitrosylated human adult hemoglobin derivative (HbNO) undergoes a reversible transition generating a 5-coordinate species, due to release of the Fe-NO bond. The overall process can be investigated using X-ray absorption near edge structure (XANES) spectroscopy. In this work, Fe K-edge XANES spectra were measured at T < 15 K, pH 9.2, i.e., on a high-affinity state (R-HbNO) where all the hemes are 6-coordinate, and at pH 6.5 in the presence of inositol hexakis-phosphate (IHP), i.e., on a low-affinity ligated state (T-HbNO) where the iron-hemes of the α-chains are 5-coordinate due to breaking of the Fe-proximal histidine bond. Under X-ray irradiation, 5-coordinate Fe-hemes are populated in both R-HbNO and T-HbNO, the Fe-NO bond lysis induced in T-HbNO involving rebinding of the proximal histidine to the transiently populated 4-coordinate hemes of the α-chains. A detailed analysis of the spectra confirms that different intermediate states in the ligand binding cooperative process of hemoglobin can be populated by X-ray irradiation, and that the part of the energy associated to the R-T quaternary transition, that is transmitted to the heme site, can be monitored by XANES spectroscopy.     

1H, 13C, 15N NMR coordination shifts in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2':6',2″-terpyridine

(1)H, (13)C and (15)N NMR studies of iron(II), ruthenium(II) and osmium(II) bis-chelated cationic complexes with 2,2':6',2″-terpyridine ([M(terpy)(2) ](2+) ; M = Fe, Ru, Os) were performed. Significant shielding of nitrogen-adjacent H(6) and deshielding of H(3'), H(4') protons were observed, both effects being mostly expressed for Fe(II) compounds. The metal-bonded nitrogens were shielded, this effect being much larger for the outer N(1), N(1″) than the inner N(1') atoms, and enhanced in the Fe(II) → Ru(II) → Os(II) series.     

Liquid crystalline properties of new unsymmetrical compounds with benzothiazole core detected by TG/DSC-POM-XRD

Thermal properties of two azomethine liquid crystals with a benzothiazole core were synthesized and investigated by applied Mettler-Toledo AG equipment (TG/DSC). Azomethines with benzothiazole core was obtained by nucleophilic addition of benzothiazole-2-carboxaldehyde in N,N-dimethylacetamide (DMA) solution with 4-(heptadecafluoroctyl)aniline (BTA1) or 4-hexadecylaniline (BTA2). The differential scanning calorimetry (DSC) was employed to evaluate their phase transitional behavior. Variable heating and cooling rates were used to study liquid crystalline properties of azomethines with benzothiazole core. Compound BTA1 exhibited liquid crystalline properties, while BTA2 is non-mesogenic. Three or four endothermic DSC peaks were observed for both compounds during heating process with the rate 0.5?°C/min. The mesophase was identified and confirmed by XRD study and polarized optical microscopy (POM) too. The thermal stability was determined by thermogravimetric analysis (TG). The temperatures of 5% mass loss (T _5%) of BTA1 and BTA2 range from 212 to 317?°C in nitrogen.     

The K-functional for p-convexifications

The $K$ -functional of Peetre is calculated for $p$ -convexifications of normed ideal space as an answer to Lozanovski? problem.     

Generalized Topological Essentiality and Coincidence Points of Multivalued Maps

A concept of generalized topological essentiality for a large class of multivalued maps in topological vector Klee admissible spaces is presented. Some direct applications to differential equations are discussed. Using the inverse systems approach the coincidence point sets of limit maps are examined. The main motivation as well as main aim of this note is a study of fixed points of multivalued maps in Fréchet spaces. The approach presented in the paper allows to check not only the nonemptiness of the fixed point set but also its topological structure.      

Semiclassical Weyl Formula for a Class of Weakly Regular Elliptic Operators

We investigate the semiclassical Weyl formula describing the asymptotic behaviour of the counting function for the number of eigenvalues in the case of self-adjoint elliptic differential operators satisfying weak regularity hypotheses. We consider symbols with possible critical points and with coefficients which have Hölder continuous derivatives of first order. Mathematics Subject Classification (2000) 35P20.