Characterization of flavonoid and naphthopyranone derivatives from Eriocaulon ligulatum using liquid chromatography tandem mass spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Alkamides and phenethyl derivatives from Aristolochia gehrtii

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and thermal study of the barium complexes with 8-hydroxyquinolinate derivatives

In this present work, barium ion was reacted with different ligands which are 5,7-dibromo, 5,7-dichloro, 7-iodo and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring and the obtained compounds were as follows: (I) Ba[(C9H4ONBr2)(2)].1.5H(2)O; (II) Ba[(C9H4ONCl2)(OH)]. 1H(2)O; (III) Ba[(C9H5ONI)(2)]. 1H(2)O and (IV) Ba[(C9H4ONICl)(2)]. 5H(2)O, respectively. The compounds were characterized by elemental analysis, infrared absorption spectrum (IR), inductively coupled plasma spectrometry (ICP), simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning calorimeter (DSC).The final residue of the thermal decomposition was characterized as orthorhombic BaBr2 from (I); the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and cubic BaO and the final residue, as a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 (II); the intermediate residue, as orthorhombic BaCO3 and as a final residue, a mixture of cubic and tetragonal BaO from (III); and the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and as a final residue, a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 from (IV).

Surface pressure-area isotherms for Langmuir monolayers and a docking molecular orientation of perylene tetracarboxylic derivatives on a water surface

The surface pressure-molecular area (pi-A) isotherms for Langmuir monolayers of four perylenetetracarboxylic (PTCD) derivatives, measured with varying subphase temperatures and compression speeds, are reported. The behavior of these PTCD derivatives at the water-air interface is modeled using the rigid docking method. This approach is the first attempt to model the molecular orientation of PTCD on the water surface to be compared with experimental Langmuir isotherms. Through this methodology, it would be possible to anticipate aggregation and determine if favorable spatial orientations of perylenes are generated on the water surface. The pi-A isotherm experiments show that these molecules can support high surface pressures, indicating strong packing on the water surface and that the isotherms are compression speed independent but temperature dependent. The molecular orientation and stacking was further examined in Langmuir-Blodgett (LB) monolayers deposited onto glass and glass coated with Ag island films using UV-visible absorption and surface-enhanced fluorescence (SEF) measurements.

Gaussian basis sets to the theoretical study of the electronic structure of perovskite (LaMnO3)

The Generator Coordinate Hartree-Fock (GCHF) method is applied to generate extended (20s14p), (30s19p13d), and (31s23p18d) Gaussian basis sets for the 0, Mn, and La atoms, respectively. The role of the weight functions (WFs) in the assessment of the numerical integration range of the GCHF equations is shown. These basis sets are then contracted to [5s3p] and [11s6p6d] for 0 and Mn atoms, respectively, and [17s11p7d] for La atom by a standard procedure. For quality evaluation of contracted basis sets in molecular calculations, we have accomplished calculations of total and orbital energies in the Hartree-Fock-Roothaan (HFR) method for (MnO1+)-Mn-5 and (LaO1+)-La-1 fragments. The results obtained with the contracted basis sets are compared with values obtained with the extended basis sets. The addition of one d polarization function in the contracted basis set for 0 atom and its utilization with the contracted basis sets for Mn and La atoms leads to the calculations of dipole moment and total atomic charges of perovskite (LaMnO3). The calculations were performed at the HFR level with the crystal [LaMnO3](2) fragment in space group C-2v the values of dipole moment, total energy, and total atomic charges showed that it is reasonable to believe that LaMnO3 presents behaviour of piezoelectric material. (C) 2003 Elsevier B.V. All rights reserved.

Catalysis and temperature dependence on the formation of ZnO nanoparticles and of zinc acetate derivatives prepared by the sol-gel route

The chemical and structural nature of powders prepared from the zinc acetate-derived precursor using the sol-gel route is discussed. The influence of the synthesis temperature and of the hydrolytic catalyst on the structural features of the powder is focused on the basis of X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) measurements and complemented with density and thermoanalysis (TG-DTA) results. EXAFS and XRPD results show that no-washed nanoparticulate powders are composed of a mixture of ZnO (wurtzite), zinc acetate, and zinc hydroxyacetate. The latter has a layered structure typical of hydroxy double salts (HDS). The main component of no-washed powders is always unreacted zinc acetate solid but the relative amount of the zinc-based compounds depends on the nature of the hydrolytic catalyst, hydrolysis ratio, and of synthesis temperature. According to the proportion of the three zinc-based compounds, three families of powders could be distinguished. The amount of ZnO nanoparticles (1.6 +/- 0.6 nm) decreases as the synthesis temperature increases, as the hydrolysis ratio decreases, or by changing from basic to acid catalysis. This finding suggests that the formation of zinc compounds is controlled by the equilibrium between hydrolysis-condensation and complexation-reprecipitation reactions.

Sublimation/volatilisation kinetics of 8-hydroxyquinolines and their nitro-derivatives

5-Nitro-8-hydroxyquinoline (B) and 5,7-dinitro-8-hydroxyquinoline (C) were obtained from nitration of 8-hydroxyquinoline (A) and purified in acetone medium and under heating in which the formation of (B) or (C) depends on the amount of HNO3 added. TG curves present mass loss in only one step before and after the melting point (T-m=76 degreesC (A) and 180 degreesC (B)) in different proportions as a function of the heating rate, characterising the sublimation and the volatilisation processes, respectively. The thermal stability of the compounds follow the order: A (77 degreesC)

ELECTROACTIVE BLENDS OF POLY(VINYLIDENE FLUORIDE) AND POLYANILINE DERIVATIVES

The conditions for processing and doping of blends of poly(o-alkoxyaniline)s and poly(vinylidene fluoride) were investigated. Flexible, free-standing and stretchable films of blends of various compositions were obtained by casting. A low percolation threshold was observed with the onset of conductivity at low polyalkoxyaniline contents (i.e. 5%). Interestingly, these blends displayed electrochromism with colour changes similar to those of the parent conducting polymer, as observed from cyclic voltammetry measurements. This behaviour is seen even for low contents of the conducting polymer, indicating that a continuous conducting pathway, which is capable of exchanging charge, is formed within the insulating matrix.

The generator coordinate Hartree-Fock method as strategy for building Gaussian basis sets to ab initio study of the process of adsorption of sulfur on platinum (200) surface

The scheme named generator coordinate Hartree-Fock method (GCHF) is used to build (22s14p) and (33s22p16d9f) gaussian basis sets to S ((3)P) and Pt ((3)D) atoms, respectively. Theses basis sets are contracted to [13s10p] and [19s13p9d5f] through of Dunning's segmented contraction scheme and are enriched with d and g polarization functions, [13s10p1d] and [19s13p9d5flg]. Finally, the [19s13p9d5f1g] basis Set to Pt ((3)D) was supplemented with s and d diffuse functions, [20s13p10d5flg], and used in combination with [13s10p1d] to study the effects of adsorption of S ((3)D) atom on a pt ((3)D) atom belonged to infinite Pt (200) surface. Atom-atom overlap population, bond order, and infrared spectrum of [pt(_)S](2 -) were calculated properties and were carried out at Hartree-Fock-Roothaan level. The results indicate that the process of adsorption of S ((3)P) on pt ((3)D) in the infinite Pt (200) surface is mainly caused by a strong contribution of sigma between the 3p(z) orbital of S ((3)P) and the 6s orbital of pt ((3)D). (c) 2004 Elsevier B.V. All rights reserved.

AN INVESTIGATION OF THE ELECTRONIC-STRUCTURE OF THE ANTITUMOR DRUG ELLIPTICINE AND ITS DERIVATIVES .1. GEOMETRICAL AM1 STUDY

Ellipticine and its derivatives are a class of molecules that show antitumor and cytotoxic activity with a multimodal mechanism of action. In this paper we report a preliminary Austin Method One (AM1) study of ellipticine and some molecules derived from it. We have observed a relationship between charge density distribution and biological selectivity. A mechanism that could improve cytotoxic activity is proposed.

Synthesis and thermal study of magnesium complexes with 8-hydroxyquinolinate derivatives

Magnesium ion was reacted with 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring to obtain (I) Mg[(C9H4ONBr2)(2)].2H(2)O; (II) Mg[(C9H4ONCl2)(2)].3H(2)O; (III) Mg[(C9H5ONI)(2)].2H(2)O and (IV) Mg[(C9H4ONICl)(2)].2.5H(2)O complexes. The compounds were characterized by elemental analysis, IR spectra, ICP, TG-DTA and DSC.Through thermal decomposition residues were obtained and characterized, by X-ray diffractometry, as a mixture of hexagonal MgBr2 and cubic MgO to the (I) compound at 850degreesC; cubic MgO to the (II), (III) and (IV) compounds at 750, 800 and 700degreesC, respectively.

Design of Gaussian basis sets to the theoretical interpretation of IR-spectrum of hexaaquachromium (III) ion, tetraoxochromium (IV) ion, and tetraoxochromium (VI) ion

The Generator Coordinate Hartree-Fock (GCHF) method is employed to design 16s, 16s10p, 24s17p13d, 25s17p13d, and 26s17p Gaussian basis sets for the H ((2)S), O ((3)P), O(2-) ((1)S), Cr(3+) ((4)F), Cr(4+) ((3)F), and Cr(6+) ((1)S) atomic species. These basis sets are then contracted to (4s) for H ((2)S), (6s4p) for O ((3)P), and O(2-) ((1)S), (986p3d) for Cr(3+) ((4)F), (10s8p3d) for Cr(4+) ((3)F), and (13s7p) for Cr(6+) (1S) by a standard procedure. For evaluation of the quality of those basis sets in molecular calculations, we have accomplished studies of total and orbital (HOMO and HOMO-1) energies at the HF-Roothaan level for the molecular species of our interest. The results obtained with the contracted basis sets are compared to the values obtained with our extended basis sets and to the standard 6-311G basis set from literature. Finally, the contracted basis sets are enriched with polarization function and then utilized in the theoretical interpretation of IR-spectrum of hexaaquachromium (III) ion, [Cr(H(2)O)(6)](3+), tetraoxochromium (IV) ion, [CrO(4)](4-), and tetraoxochromium (VI) ion, [CrO(4)](2-). The respective theoretical harmonic frequencies and IR-intensities were computed at the density functional theory (DFT) level. In the DFT calculations we employed the Becke's 1988 functional using the LYP correlation functional. The comparison between the results obtained and the corresponding experimental values indicates a very good description of the IR-spectra of the molecular ions studied, and that the GCHF method is still a legitimate alternative for selection of Gaussian basis sets. (C) 2003 Elsevier B.V. All rights reserved.

Quantitative determination of cytotoxic friedo-nor-oleanane derivatives from five morphological types of Maytenus ilicifolia (Celastraceae) by reverse-phase high-performance liquid chromatography

Five different morphological types of Maytenus ilicifolia of the same age and harvested under the same conditions showed distinct accumulations of some friedo-nor-oleananes. A rapid, sensitive and reliable reverse-phase HPLC method (employing an external standard) was used for the determination of the cytotoxic triterpenoids, 20alpha-hydroxymaytenin, 22beta-hydroxymaytenin, maytenin, celastrol and pristimerin in each of the five types. Well resolved peaks with good detection response and linearity in the range 1.0-100 mug/mL were obtained. Copyright (C) 2002 John Wiley Sons, Ltd.