5‐Nitro‐N‐phenyl‐2‐thio­fur­amide

The title compound, C₁₁H₈N₂O₃S, crystallizes with two crystallographically independent mol­ecules, which are conformationally almost identical, per asymmetric unit. The dihedral angles between the phenyl and 2‐thio­fur­amide planes are 46.3 (1) and 47.0 (1)° for the first and second mol­ecule, respectively. Strong intramolecular N—H?O hydrogen bonds [N?O 2.664 (2) and 2.661 (2) Å] dictate an anti conformation of the C=S groups in relation to the furan‐O atoms.     

3‐[(2‐Oxo‐1‐naphthylidene)methyl­amino]­benzoic acid

The title compound, C₁₈H₁₃NO₃, exists as a keto­amino tautomer implying a fairly short N—H?O intramolecular hydrogen bond between the 2‐naphthalenone and amino moieties [N?O 2.531 (3) Å] which is enhanced by the π‐electron delocalization effect. The naphthald­imine and 3‐carboxy­phenyl fragments are inclined at an angle of 4.41 (7)°, so the mol­ecule is almost planar. The mol­ecules are connected by intermolecular O—H?O hydrogen bonds between the carboxy and keto O atoms, forming infinite chains around the twofold screw axes parallel to b .     

Synthesis and biological evaluation of two novel 2′-substituted tiazofurin analogues

Two novel tiazofurin analogues, 2-(2-benzamido-2-deoxy-β-d-ribofuranosyl)thiazole-4-carboxamide 4 and 2-(2-azido-2-deoxy-β-d-ribofuranosyl)thiazole-4-carboxamide 5, have been synthesized starting from d-glucose and evaluated for their in vitro cytotoxicity against several human leukaemia and solid tumour cell lines.     

Diamond coating deposition by synergy of thermal and laser methods—A problem revisited

Diamond coatings were deposited by synergy of the hot filament CVD method and the pulse TEA CO₂ laser, in spectroactive and spectroinactive diamond precursor atmospheres. Resulting diamond coatings are interpreted relying on evidence of scanning electron microscopy as well as microRaman spectroscopy. Thermal synergy component (hot filament) possesses an activating agent for diamond deposition, and contributes significantly to quality and extent of diamond deposition. Laser synergy component comprises a solid surface modification as well as the spectroactive gaseous atmosphere modification. Surface modification consists in changes of the diamond coating being deposited and, at the same time, in changes of the substrate surface structure. Laser modification of the spectroactive diamond precursor atmosphere means specific consumption of the precursor, which enables to skip the deposition on a defined substrate location. The resulting process of diamond coating elimination from certain, desired locations using the CO₂ laser might contribute to tailoring diamond coatings for particular applications. Additionally, the substrate laser modification could be optimized by choice of a proper spectroactive precursor concentration, or by a laser radiation multiple pass through an absorbing medium.     

High Pressure effect on fluorescence lifetime τ for magnetic dipole 5D0→5F1 transitions in YAG:Eu3+

The fluorescence lifetime for magnetic dipole ⁵D₀→⁷F₁ transition in yttrium aluminum garnet doped with Eu³⁺ (YAG:Eu³⁺) crystal was studied under the pressure of up to 10.4?GPa at room temperature. The fluorescence lifetime τ (⁵D₀→⁷F₁ transition) slowly decreased with pressure. The pressure effect on τ (⁵D₀→⁷F₁ transition) was explained with a model which considered pressure effect on line position: inter-ionic distance, ion volume, molecular volume, ion polarizability, molecular polarizability, sample refractive index, and surrounding hydrostatic medium refractive index. The fluorescence lifetime τ calculated by the presented model was in close correspondence with the experimental values.     

Solvent and Structural Effects on the UV–Vis Absorption Spectra of Some 4,6-Disubstituted-3-Cyano-2-Pyridones

A series of 4,6-disubstituted-3-cyano-2-pyridones was synthesized and their UV?CVis absorption spectra were recorded in the region 200?C600?nm in the set of selected solvents. The effects of solvent dipolarity/polarizability and solvent?Csolute hydrogen-bonding interactions on the spectral shifts were analyzed by means of the linear solvation energy relationship concept of Kamlet and Taft. The influence of solvents as well as substituents on the 2-pyridone/2-hydroxypyridine tautomeric equilibration was evaluated. The absorption band maximum of the 2-hydroxypyridine form is found to appear at a shorter wavelength than that of the 2-pyridone form in all investigated solvents. The replacement of the methyl and phenyl groups at position 6 of the pyridone ring, by a hydroxy group, significantly changes the solvatochromic behavior of the investigated pyridones.     

Development and Evaluation of a Kinetic‐Spectrophotometric Method for Determination of Arginine

A kinetic method for the determination of micro quantities of amino acid arginine (Arg) is described in this paper. The catalytic activity of cobalt in the reaction of oxidation of purpurin (1,2,4‐trihydroxy‐antraquinone, PP) by hydrogen peroxide in alkaline buffer solution decreases in the presence of micro quantities of arginine, because of the formation of the complex. Operating conditions for the successful determination of arginine were optimized. The optimized conditions yielded a theoretical detection limit of 1.45 μg mL^?1. Kinetic equations are proposed for the investigated process. The interference effects of certain foreign ions and amino acids upon the reaction rate were studied and removed in order to assess the selectivity of the method. The developed procedure was successfully applied to the determination of arginine in various pharmaceutical samples. The typical feature of this procedure is that determination can be carried out at room temperature and in a short analysis time. The newly developed method is simple, inexpensive and efficient for use in the analysis of a large number of samples.     

Parenchyma cell wall structure in twining stem of <Emphasis Type="Italic">Dioscorea balcanica</Emphasis>

Anatomical adaptation of liana plants includes structural changes in cell walls of different tissues: fibers, vessel elements and tracheids. However, the contribution of parenchyma cells to stem twining in liana plants is mostly unknown. The aim of this investigation is to determine changes in stem parenchyma cell walls that are correlated with the twinning process in liana plants. Parenchyma cell wall structure was studied on the stem cross sections of straight and twisted internodes of monocotyledonous liana Dioscorea balcanica, by different microscopy techniques: light microscopy, scanning electron microscopy, fluorescence detected linear dichroism microscopy and Fourier transform infrared microspectrometry. In addition, chemical analysis of the entire stem internodes was performed using photometric and chromatographic methods. Parenchyma cell walls of twisted D. balcanica internodes are characterized by: lower amounts of cellulose (obtained by FTIR microspectrometry) with different cellulose microfibril orientation (shown by Scanning electron microscopy), but no changes in “cellulose fibril order” (obtained by Differential polarization laser scanning microscopy); lower amounts of xyloglucan, higher amounts of xylan, higher amounts of lignin with modified organization—less condensed lignin (obtained by FTIR microspectrometry). At the same time, chemical analysis of the entire internodes did not show significant differences in lignin content and cell wall bound phenols related to stem twining, except for the presence of diferulate cross-links exclusively in twisted internodes. Our results indicate that adaptations to mechanical strain in D. balcanica stems involve modifications in parenchyma cell wall structure and chemistry, which provide decreased stiffness, higher strength and increased elasticity of twisted internodes.     

Supramolecular solid-state structure,potential energy surfaces and evaluation of antiproliferative effect of 2-benzothiazolylhydrazone derivatives in vitro

The in situ condensation reaction of 2-hydrazinobenzothiazole with salicylaldehyde, 3,4-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, 2-methoxy-1-naphthaldehyde, 4-methoxy-1-naphthaldehyde and 6-methoxy-2-naphthaldehyde produced 9 hydrazone Schiff bases (L1–L9, respectively) which were identified and characterized by elemental analysis, IR and NMR spectroscopy. The crystal and molecular structures of four Schiff bases (L1, L7–L9) have been determined by the single-crystal X-ray diffraction method confirming the imino form of L1 and the amino tautomeric form of L7–L9 compounds. Molecular structure analysis also confirmed that reported compounds are E-isomers relative to exo C = N imino bond. The N_hydrazino–H group of amino tautomers forms N_hydrazino–H···N_thiazolyl intermolecular hydrogen bonds shaping molecules into R ₂ ² (8) rings, while imino tautomer of L1 forms C(4) infinite helical chains via N_thiazolyl–H···N_hydrazino type of intermolecular hydrogen bond. The methoxy group (L7–L9) further shaped these primary supramolecular synthons into different supramolecular arrangements via C–H···O, C–H···N and C–H···S intermolecular hydrogen bonds. The role of aryl substituents in the shaping and stabilization of supramolecular architectures of L1, L7–L9 is supported by quantum chemical calculations. Strong antiproliferative effects on tumor cells and cytotoxic effects on fibroblasts are shown for all ligands L1–L9 with exception of L6 and L7 that had no effect on fibroblast cells.