Navegando por Autor "Carvalho, Carlos Alberto Alves de"
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Item Dehydrocrotonin and its h-cyclodextrin complex : Cytotoxicity in V79 fibroblasts and rat cultured hepatocytes.(2005) Corrêa, Daniel Henrique do Amaral; Melo, Patrícia Silva; Carvalho, Carlos Alberto Alves de; Azevedo, Mariângela de Burgos Martins de; Durán, Nelson; Haun, MarcelaTrans-dehydrocrotonin has antiulcerogenic and antitumor activities. A complex of h-cyclodextrin with dehydrocrotonin was developed to improve the delivery of dehydrocrotonin. Complex in solid state was evaluated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). X-ray diffraction and scanning electron microscopy studies showed that dehydrocrotonin exists in a semicrystalline state in the complexed form with h-cyclodextrin. Differential scanning calorimetry studies showed the existence of a complex of dehydrocrotonin with h-cyclodextrin. The thermal gravimetric analysis studies confirmed the differential scanning calorimetry results of the complex. Free dehydrocrotonin and the dehydrocrotonin/h-cyclodextrin inclusion complex were assayed in freshly isolated rat hepatocytes and in V79 cells. Cytotoxicity was determined using nucleic acid content, methylthiazoletetrazolium (MTT) reduction and neutral red uptake assays. In all assays, there was a large reduction (3.5–16.1-fold) in the cytotoxicity of dehydrocrotonin in hepatocytes when complexed with h-cyclodextrin, whereas for V79 cells the decrease in cytotoxicity was 1.7- and 1.87-fold for MTT reduction and nucleic acid content assays, respectively. The lower cytotoxicity of the dehydrocrotonin/hcyclodextrin complex compared to free dehydrocrotonin in rat hepatocytes and V79 cells suggests that such a complex may be useful for the administration of dehydrocrotonin in vivo.Item Luminescence behavior of Eu3+ with thenoyltrifluoroacetonate, sulfoxides and macrocyclics.(1998) Brito, Hermi Felinto de; Malta, Oscar Manoel Loureiro; Carvalho, Carlos Alberto Alves de; Menezes, Jorge Fernando Silva de; Souza, L. R.; Ferraz, ReginaldoIn this work we present a study of the luminescence intensity of Eu(TTA) ?xL, where TTA5thenoyltrifluoroacetonate (L denotes 3 DBSO and PTSO sulfoxides, and derivatives of 15C5 and 18C6 macrocyclics). The complexes with 15-crown-5 ether ligand contain two H O molecules. The complexes were characterized by a microanalytical procedure, IR spectroscopy and molar conductance. They show 2 31 high luminescence mainly in the red region. The characteristic emission spectra of Eu in these compounds show uncommonly high 5 7 values of the V intensity parameters, reflecting the hypersensitive behavior of the D F transition and indicating that the rare earth 2 0 2 5 7 ion is in a highly polarizable chemical environment. The D F transition splitting, in the case of Eu(TTA) ?18C6, indicates more than 0 0 3 31 one site of symmetry occupied by Eu .Item Luminescence investigation of the Sm(III)-b-diketonates with sulfoxides, phosphine oxides and amides ligands.(2002) Brito, Hermi Felinto de; Malta, Oscar Manoel Loureiro; Felinto, Maria Claudia França da Cunha; Teotonio, Ercules Epaminondas de Sousa; Menezes, Jorge Fernando Silva de; Silva, C. F. B.; Tomiyama, C. S.; Carvalho, Carlos Alberto Alves deIn this paper we report on a photoluminescent investigation of complexes involving Sm -b-diketonates with sulfoxides, phosphine oxides and amides ligands. In the synthesis of the coordination compounds we used samarium tris(thenoyltrifluoroacetonate) dehydrated precursor with the following ligands (L): DBSO and PTSO sulfoxides; TPPO phosphine oxide and (PHA) N-phenylacetamide. They have 31 31 shown high orange luminescence characteristic of the Sm ion. The emission spectra of the Sm -complexes present narrow bands 4 6 4 6 arising from the G →H (J55/ 2, 7/ 2, 9/ 2, 11/2) transitions with the hypersensitive G →H transition as a prominent group. It 5 / 2 J 5 / 2 9/ 2 4 31 is observed an efficient intramolecular energy transfer from the triplet state (T) of the ligands to the emitting G state of the Sm ion. 5 / 2 The experimental intensity parameters (h andh ) for the Sm and Eu complexes have been determined and compared. The lifetimes (t ) Sm Eu 4 of the emitting level G of the Sm-complexes are approximately 10 times higher than in the precursor compound [Sm(TTA) ?(H O) ] 5 / 2 3 2 2 indicating that radiative processes are operative in all the compounds due to the absence of multiphonon relaxation by coupling with the OH oscillators.Item Persistent luminescence of Eu2+ and Dy3+ doped barium aluminate (BaAl2O4:Eu2+,Dy3+) materials.(Optical Materials, 2009) Stefani, Roberval; Rodrigues, Lucas Carvalho Veloso; Carvalho, Carlos Alberto Alves de; Felinto, Maria Claudia França da Cunha; Brito, Hermi Felinto de; Lastusaari, Mika; Hölsä, JormaPolycrystalline Eu2+ and Dy3+ doped barium aluminate materials, BaAl2O4:Eu2+,Dy3+, were prepared with solid state reactions at temperatures between 700 and 1500 _C. The influence of the thermal treatments on the stability, homogeneity and structure as well as to the UV-excited and persistent luminescence of the materials was investigated by X-ray powder diffraction, SEM imaging and infrared spectroscopies as well as by steady state luminescence spectroscopy and persistent luminescence decay curves, respectively. The IR spectra of the materials prepared at 250, 700, and 1500 _C follow the formation of BaAl2O4 composition whereas the X-ray powder diffraction of compounds revealed how the hexagonal structure was obtained. The morphology of the materials at high temperatures indicated important aggregation due to sintering. The luminescence decay of the quite narrow Eu2+ band at ca. 500 nm shows the presence of persistent luminescence after UV irradiation. The dopant (Eu2+) and co-dopant (Dy3+) concentrations affect the crystallinity and luminescence properties of the materials.Item Positronium formation in lanthanide (III) trifluoroacetate with 3-picoline-N-oxide compounds.(2001) Netto, Antônio Marques; Carvalho, Cornélio de Freitas; Carvalho, Carlos Alberto Alves de; Sinisterra, Ruben Dario; Brito, Hermi Felinto de; Machado, José CaetanoPositron annihilation lifetime and Doppler broadening annihilation radiation line shape on the salts Ln(CF3COO)3•xH2O and the adducts Ln(CF3COO)3(3-picNO)•xH2O (Ln=La–Pr, Sm–Lu and Y, and 3-picNO=3picoline-N-oxide, x in the range 0.75–1.33) were performed. Positroniumformation in the adducts, except for the europium complex, was observed. These results are discussed in terms of the electronic properties of the central metal ions.Item Spectroscopic study of the inclusion compound of b-cyclodextrin and Tris(dibenzoylmethane)europium(III) dehydrate.(1999) Brito, Hermi Felinto de; Carvalho, Carlos Alberto Alves de; Malta, Oscar Manoel Loureiro; Passos, J. J.; Menezes, Jorge Fernando Silva de; Milan, Ruben Dario SinisterraPhotoluminescent properties of the inclusion compound of b-cyclodextrin and tris(dibenzoylmethane)europium(III) dihydrate, in the solid state, are reported. This compound and the precursor salt, Eu(DBM)3 • 2H2O (DBM_dibenzoylmethane), were characterized by IR spectroscopy, X-ray powder diffraction and differential scanning calorimetry. The emission data indicate that the host-guest interaction (at 77 K) causes an intensification of some bands corresponding to the 5D0.7FJ (J_0–4) transitions associated with one of the site symmetries existing in the guest compound. Based on the luminescence spectrum of the supramolecular compound the Vl experimental intensity parameters (l_2 and 4) were calculated for the electronic transitions 5D0.7F2, 4. The value of the V2 intensity parameter for this new compound is smaller than for the guest, suggesting an effective interaction between the b-cyclodextrin and the closer chemical environment of the Eu3_ ion. On the other hand, the values of the V4 parameter for the inclusion compound are twice larger than the one of the guest, suggesting that the steric effect is more significant in the supramolecular species. Comparison between the luminescence lifetimes of the guest and inclusion compound indicates that the b-cyclodextrin contributes to increase the lifetime of the 5D0 emitting level. The time-resolved spectra of the inclusion compound corroborate the presence of more than one site symmetry occupied by the rare earth ion.Item Studies of the interaction of the salicylideneserinatecopper(II) complex with β-cyclodextrin : characterization and reactivity of the inclusion compound.(1999) Sinisterra, Ruben Dario; Mielli, Renata Vicentini; Carvalho, Carlos Alberto Alves de; Silva, Wendel Gomes da; Mangrich, Antonio Salvio; Ferreira, Ana Maria da CostaThe compound formed by the copper-Schiff base complex salicylideneserinatecopper(II), [Cu(sal-ser)(H2O)], interacting with β-cyclodextrin was prepared, and characterized in the solid state by infrared, UV-visible and EPR spectroscopies, X-ray diffraction, and thermoanalytical techniques. The catalytic activity of this compound, [Cu(sal-ser)CD], in the decomposition of hydrogen peroxide, and in the dismutation of superoxide radicals was also verified, in comparison with the reactivity of the free complex, in aqueous solution. In both cases, a decreasing in the reaction rate was observed for the CD-containing compound. The results of structural characterization, in addition to the substantial differences observed in the catalytic activities of the compounds, are indicative of partial insertion of the copper complex in the cavity of the oligosaccharide.Item Study of the thermal decomposition of the Nd(III), Eu(III) and Tb(III) scorpionates.(2002) Miranda Júnior, Pedro; Aricó, Eliana Maria; Máduar, Marcelo Francis; Matos, Jivaldo do Rosário; Carvalho, Carlos Alberto Alves deThe thermal behavior of the compounds [κ3HB(N2C3H3)3]3Ln (Ln=Nd, Eu and Tb) was investigated through TG/DTG and DSC analyses. TG/DTG experiments were performed in a TGA-50 Shimadzu instrument under dynamic air atmosphere (50 ml min−1). DSC measurements were performed in a dynamic nitrogen atmosphere (50 ml min−1) at 10 °C min−1 heating rate using a DSC-50 Shimadzu differential calorimeter. For the TG/DTG and DSC analyses, an amount of 1.5–2.0 mg was used. From the TG curves, it was possible to show that all compounds are anhydrous, a one-step mass loss occurring between 200 and 450 °C, yielding a residual stable up to 900 °C. From the DTG curves it was found that decomposition temperatures decrease as the Ln(III) ionic radius decreases. DSC curves indicate that the compounds do not melt before the decomposition. For all three compounds, the decomposition process is exothermic.Item Synthesis and characterization of lanthanide trifluoroacetate complexes with 3-picoline-N-oxide.(1992) Zinner, Léa Barbieri; Carvalho, Carlos Alberto Alves de; Zinner, KlausComplexes with composition Ln(F3C-COO)3•2(3-picNO)•ξH2O were synthesized. According to X-ray powder patterns and IR data five series of isomorphous compounds were detected: LaNd; SmEu; Gd>Tm, Y; Ho, Er, Tb; Dy, Yb, Lu. They behave as nonelectrolytes in methanol. IR spectra show a shift of νNO to lower frequencies, as compared with the free ligand, as a result of coordination through the oxygen. The bands attributed to the anions indicate two modes of coordination. The neodymium spectrum at 77 K shows that the central ion is not involved in a cubic site. Electrostatic bonds between Nd3+ and ligands were evidenced by the nephelauxetic, Sinha's parameters and covalent factor from the room temperature spectrum. Using the electronic emission spectrum, at 77 K, it was possible to conclude that europium ions present two different symmetry sites, since a splitting of the 5D0 → 7F9 band was observed. The complex species are probably polymeric or at least dimeric, and europium ions are involved in two different sites, but with the same C3ν symmetry.