Total assignments of 1H and 13C NMR spectra of isocatalpanol and a derivative of tecomaquinone

Isocatalpanol and tecomaquinone I were obtained from roots of Lippia sidoides, a medicinal plant from northeast Brazil. Reduction of tecomaquinone I with NaBH4 yielded a new derivative. Structural elucidation was done on the basis of spectral data, mainly by high-field NMR and electron ionization mass spectrometry.     

Catalytic hydrogenation of benzo[2.1.3]oxadiazoles

Hydrogenation of benzo[2.1.3]oxadiazole and its chloro derivatives, yields 4,5,6,7-tetrahydrobenzo[2.1.3]oxadiazole together with small amounts of 1,2-phenylenediamine. Benzo[2.1.3]oxadiazoles substituted with no reduction-sensitive groups are hydrogenated either to the corresponding 1,2-phenylenediamines or to mixtures containing the 4,5,6,7-tetrahydro derivatives.     

First report of the in vitro antileishmanial properties of extremophile plants from the Algarve Coast

This work reports for the first time the in vitro anti Leishmania infantum activity of acetone and dichloromethane (DCM) extracts from 25 extremophile plants from Southern Portugal. DCM extracts from Inula chritmoides and Spergularia rubra were active against axenic promastigotes and intracellular amastigotes, had anti-inflammatory properties on lipopolysaccharide (LPS)-stimulated macrophages, inhibited acetylcholinesterase and had no haemolytic activity on human erythrocytes. Eleven phenolics were identified by high-performance liquid chromatography with diode-array detection (HPLC-DAD) in I. crithmoides and one phenolic in S. rubra. Isolation and identification of the active molecules is in progress.     

The Nature of Organically Modified Ceramics as Reflected by Photophysics of Trapped HITC

Phase resolved fluorescence spectroscopy (PRFS) is used to analyze fluorescence emission decay kinetics of 1,1,3,3,3,3 -hexamethylindotricarbocyanine iodide (HITC) doped in different Organically Modified Ceramics (Ormocers), yielding information about the identity of the different environment surroundings of the organic dye. We report the first results on PRFS regarding to establish a relation between the HITC photophysics and the characteristics of the Ormocer surface. Lifetimes resolution and fractional contribution of different HITC species to the total fluorescence emission were reported. An increase in the HITC chemical stability was found for doped Ormocers in comparison to inorganic gel-glasses. Scanning and transmission electron microscopy (SEM) images of the Ormocers were showed.     

Mercury complexes with thiacrowns: the crystal structure of bis(1,4,7-trithiacyclodecane) mercury(II) hexafluorophosphate

We report the synthesis, crystal structure, and NMR spectroscopy for the mercury(II) complex with the crown thioether 1,4,7-trithiacyclodecane (10S3) , bis(1,4,7-trithiacyclodecane) mercury(II) hexafluorophosphate (1). The 10S3 ligand coordinates in tridentate fashion and readily forms a distorted bis octahedral complex, an unusual coordination geometry for Hg(II). The crystal structure shows the two 10S3 ligands arranged in a trans or anti fashion around the mercury center, yielding the meso stereoisomer. Bond distances and angles are very comparable to those found in the structure of the perchlorate salt of the complex cation although the hexafluorophosphate salt shows slightly longer and more varied Hg–S distances (2.623(2) , 2.708(2), 2.784(2) Å) with a tetragonal elongation. The ¹⁹⁹Hg¹H NMR spectrum exhibits a single resonance with a chemical shift at –596 ppm consistent with a hexakis(thioether) coordination environment around the mercury center. Crystal data for 1: C2/c, a = 19.184(3) Å, b = 15.235(2) Å, c = 11.3791(15) Å, = 123.358(2)°, V = 2777.9(6) ų, Z = 4.     

How to interpret information from proficiency test exercises concerning the relative performance of accredited laboratories

If the results from various proficiency tests are used to compare the performance of accredited and non-accredited laboratories, great care must be taken not to come to contradicting conclusions when interpreting them. This paper intends to draw the attention to various aspects that should be taken into account when trying to make conclusions from the relative performance of accredited laboratories in proficiency testing.     

Proton Affinity at the Porous Surface of SiO2-TiO2 Binary Oxides

SiO₂-TiO₂ binary oxides are typically used as solid supports for different applications, from catalysts to optics. Tailoring the pore diameter, pore size distribution, and surface area is of great importance for any of those applications. Tailoring the chemical properties of the porous surface, e.g. in terms of polarity or acidity, is of capital importance as well. Thus, in catalytic applications or in sensing devices, where diffusion of a solute through the matrix is required, the affinity/compatibility of the solute with the matrix porous surface will determine the proper work of the device. Moreover, when the sensor is based on the adsorption of an active organic molecule or biomolecule on the porous surface matrix, the proton concentration at the surface may also modify the behavior of the active molecule. In this work, the proton affinity of the porous surface is tailored by the preparation of number of SiO₂-TiO₂ binary oxides with different SiO₂/TiO₂ weight ratios. Proton affinity is studied through the incorporation of a pH indicator as bromocresol green.     

Methods for controlling the regioselection in the reaction of 3-amino-5-benzylthio-1,2,4-triazole with acetylacetaldehyde dimethyl acetal

The reaction of 3-amino-5-benzylthio-1,2,4-triazole with acetylacetaldehyde dimethyl acetal affords 2-benzylthio-5-methyl-1,2,4-triazolo[1,5a]pyrimidine or 2-benzylthio-7-methyl-1,2,4-triazolo[1,5a]pyrimidine regioselectively depending on the reaction conditions.     

Effects of π bond type,backbone size,and halogen on structural and spectroscopic properties of hydrogen‐bonded complexes of the X?H … π type between alkenes or alkynes and haloacids (HF and HCl)

The effects of CC bond type (double or triple), substituent (H or methyl), and halogen (F and Cl) on three properties of hydrogen‐bonded complexes formed between unsaturated hydrocarbons and HX (X?F, Cl) are studied. The properties comprise hydrogen bond distances (R_H), stabilization energies (SE), and frequency shifts (Δν). A 2³ factorial design technique, along with ab initio (HF and MP2) and DFT (B3LYP and PBE1PBE) calculations, has been employed. All three responses are mainly affected by the halogen, and when it is changed from F to Cl, R_H tends to increase, while SE tends to decrease. Surprisingly, the type of substituent is more important than the type of CC bond, for all three responses. Both effects tend to decrease R_H. Significant interaction effects are obtained for the type of CC bond along with the type of substituent, and for the type of substituent along with the type of halogen. Both interaction effects are smaller than the main effects and also tend to decrease R_H. The greatest SE values are obtained with PBE1 functional (BSSE + ZPE corrected values). Again, the next more important effect is due to the type of substituent, and the replacement of H by CH₃ group tends to increase SE. The effect due to the CC bond type is not significant, at all computational levels. The only interaction effect that is significant for SE (corrected) and Δν is between factors 1 (CC bond type) and 2 (substituent), but only at HF and B3LYP levels, and it tends to increase both properties. As the halogen changes from F to Cl, Δν tends to decrease. In contrast, changing the substituent from H to CH₃ leads to greater values of Δν. The effect of CC bond type is not significant at HF level, and when it is changed from double to triple Δν is decreased, at B3LYP and PBE1 levels. A suggestion as to how the results may point toward a better experimental detection of similar (π‐type) complexes is also given. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Synthesis of 4-amino-2,6-diaryl-5-cyanopyrimidines as antimicrobial agents

This article describes an efficient and facile synthesis of 11 2,4,6-trisubstituted 5-cyanopyrimidines starting from meta- and para-substituted 2-cyanocinnamonitriles and arylamidines. The synthesized heterocycles, 3a–k, were characterized by infrared (IR), ¹H NMR, ¹³C NMR, and mass spectral data. The probable mechanism of formation of the title compounds employing 2-cyanocinnamonitriles and arylamidines in the presence of a base was clarified. A preliminary screening of the antibacterial tests clearly showed that 4 out of 11 pyrimidines, 3a, 3e, 3f, and 3k, were effective against bacteria Staphyloccus aureus, Bacillus subtillis, and Pseudomonas aeruginosa. Further, the minimum inhibitory concentration (MIC) against the bacteria has been determined.