Yvonne P. Mascarenhas

Location of cerium and lanthanum cations in CeNaY and LaNaY after calcination

NaY zeolite has been ion exchanged with either Ce or La cations. Rare-earth containing Y zeolites have been calcined in the presence or absence of steam, generating Y zeolites modified with rare-earth cations, which are the main components of several cracking catalysts. The Rietveld method of structure refinement was used to determine the crystallographic positions of the rare-earth cations after the calcination step (500°C, 1 h). The results showed that, regardless of the calcination mode, both La and Ce migrate to S2 sites that are located inside the sodalite cage, whereas Na cations migrate to sites S4. The aluminum generated by the dealumination process due to the incorporation of rare-earth cations and the calcination step is located inside the sodalite cage.

Conformation of the Z19 prolamin by FTIR, NMR, and SAXS.

The alpha zein, the maize storage prolamin, is a mixture of several homologous polypeptides that shows two bands in SDS-PAGE, called Z19 and Z22. The conformation studies carried out by several authors in this mixture are conflicting. To elucidate these inconsistencies, we analyzed the conformation of the Z19 fraction, extracted from BR451 maize variety by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and small-angle X-ray scattering. The infrared results show that Z19 has 46% of alpha helix and 22% of beta sheet. The fast N-H to N-D exchange measured by (1)H NMR spectroscopy showed that Z19 is not a compact structure. The scattering measurements indicated an extended structure with 12 by 130 A. With these data, we have modeled the Z19 structure as a hairpin, composed of helical, sheet, turns, and secondary structures, folded back on itself.

Characteristics of polyaniline electropolymerized in camphor sulfonic acid

Abstract Polyaniline was electropolymerized by cyclic voltammetry in the presence of camphor sulfonic acid (CSA), and the resulting film was characterized by solubility tests, UV-Vis absorption, electron mircroscopy, X-ray diffraction and conductivity measurements. The use of the functionalized acid - CSA - made it possible to obtain the as-electropolymerized polymer (in the doped state) soluble in organic solvents such as m-cresol and chloroform. The UV-Vic spectra of PAni-CSA in m-cresol presented a free-carrier tail commencing at 1000 nm which may be attributed to secondary doping due to conformational changes of the polymer chains. After treatment with m-cresol the film exhibited an increase of conductivity reaching ca. 100 S/cm.

Rietveld refinement and solid state NMR study of Nd-, Sm-, Gd-, and Dy-containing Y zeolites

Abstract Na-Y zeolites ion exchanged with rare earth cations (Nd3+, Sm3+, Gd3+, Dy3+) were studied by X-ray diffraction in order to locate the rare earth cations in the zeolite framework and the resulting changes in its structural properties. The results indicate that the rare earth cations dealuminate the framework differently. This is observed as a decrease in the values of the unit cell parameters, a0. This systematic decrease in a0 is related to the rare earth ionic radius and its coordination to the oxygen framework. The correlation between the Si/Al ratio obtained from the Fichtner-Schmittler equation and the ionic radius of the rare earth cations reveals that smaller ionic radii gives higher dealumination and smaller a0. This is related to hydrolysis constant cation. Samples treated with Dy3+ cations show a higher level of dealumination than those treated with the other cations (Sm3+, Gd3+, Nd3+). In order to characterize the dealumination process 29 Si and 27 Al magic angle spinning NMR measurements were attempted. Except for the Sm3+ treated sample, the Nd3+, Gd3+, Dy3+ samples could not have their tetrahedral and octahedral aluminum signal detected due to the high concentration of the paramagnetic ions with large effective number of Bohr magnetons.

Tin, palladium and platinum derivatives of 1,1′-bis(diphenylphosphine)ferrocene. Crystal and molecular structures of 1,1′- bis-(diphenylphosphine)ferrocenedichloropalladium(II) and of 1,1′-bis(diphenylphosphine)ferrocenedichloroplatinum(II)

SummaryTen derivatives of 1,1′-bis(diphenylphosphine)ferrocene (BDPF) are described in this paper. The first three, [BDPF·SnCl4] (1), [BDPF·MeSnCl3] (2) and [BDPF·PhSnCl3] (3), present the two phosphorus atoms of the ligand directly bonded to a Sn centre. Two others, [BDPF-PdCl2 (4) and [BDPF·PtCl2] (5), similarly have the ligand BDPF acting as a bidentate species towards a transition metal. The crystal and molecular structures of (4) and (5) are presented here. Two other BDPF complexes were obtained with Pd and Pt, with the transition metals in the zerovalent state, namely [Pd(BDPF)2] (6) and [Pt(BDPF)2] (7). Finally, three trimetallic complexes are also described; [BDPF·Pd(μ-Cl)2SnCl2] (8), [BDPF· Pt(μ-Cl)2SnCl2] (9) and [BDPF·PdClSnCl3] (10).

Synthesis, crystal structure and properties of a new binuclear iron(III) complex as a model for the purple acid phosphatases

Abstract The new binucleating ligand 2,6-bis[(2-hydroxybenzyl)(2- pyridylmethyl)-amino-methyl]-4-methylphenol, (H3BBPMP), has been prepared. The reaction of H3BBPMP with Fe(ClO4)2·6H2O in the presence of sodium acetate in methanolic solution affords the title complex, [Fe2(BBPMP)(OAc)2]ClO4·H2O (1). The crystal structure of 1 has been determined by X-ray cystallography. Crystal data: monoclinic, space group P21/n a=14.863(5), b=12.315(3), c=20.872(8) A, β=90.83(3)°, Z=4. Electrochemical, magnetic and electronic structural as well as Mossbauer spectral properties of 1 have been investigated. Some of these properties indicate that complex 1 represents an interesting model for the purple acid phosphatase active site.

Absolute configuration of the benzofuranoid neolignans

Abstract The benzofuranoid neolignans, classified into structurally homogeneous groups by constitution and ORD curves, have had their relative configurations es

Structural characterization of emeraldine-salt polyaniline/gold nanoparticles complexes

Gold nanoparticles (Au NPs) stabilized with polyamidoamine dendrimers (Au-PAMAM) or sodium citrate (Au-CITRATE) were synthesized and complexed with polyaniline emeraldine-salt form (ES-PANI). The complexes were characterized using structural and morphological techniques, including X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Zeta Potential analyses, and Fourier-Transformed Infrared spectroscopy (FTIR). When the Au-CITRATE NPs are added to the polymeric solution, the formation of a precipitate is clearly observed. The precipitate exhibited a different morphology from that found for ES-PANI and Au-CITRATE NPs, suggesting the formation of ES-PANI coating over the surface of Au-CITRATE NPs. On the other hand, when the Au-PAMAM NPs are incorporated into the ES-PANI solution, none interaction was observed, probably due to the repulsive electrostatic interactions, being the organization of the ES-PANI chains unaffected by the presence of the Au-PAMAM NPs.

A study of the highly crystalline, low-silica, fully hydrated zeolite P ion exchanged with (Mn2+, Cd2+, Pb2+, Sr2+, Ba2+) cations

Abstract An extensive study of a highly crystalline of sodium maximum aluminum zeolite P (Na–MAP) ion exchanged with Mn2+, Cd2+, Pb2+, Sr2+, and Ba2+ cations and with a Si/Al ratio of 1.0, is presented. All the crystal structures were refined from conventional X-ray powder data in the monoclinic crystal system, space group P21/c, and have the GIS framework topology. The Cd–MAP and Mn–MAP structures are similar to that of Ca-gismondine and the positions of the Cd and Mn atoms match the cations positions in natural Ca-gismondine. The Ba–MAP, Sr–MAP and Pb–MAP structures, however, are quite different. The unit cells of Ba–MAP and Pb–MAP are metrically orthorhombic, but their structures were refined with the monoclinic space group P21/c. Sr–MAP, in contrast to the other structures, presents two sites for the extra-framework cations. The incorporation of Cd, Mn, Ba, Sr, and Pb cations produces different distortions in the GIS framework due to its high flexibility. Besides the distortions induced by the cation incorporation, the 29Si NMR data and the Si–O and Al–O bonds show that all structures present a strict ordering scheme of Si and Al. The number of water molecules per unit cell differs between the title compounds, as does their dehydration behaviour. Dehydration of Cd–MAP and Mn–MAP induces the formation of new phases. However, under rehydration conditions, these new phases are restored to the original ones. On the other hand, dehydration of Sr–MAP and Pb–MAP induces the formation of new phases that are unchanged under rehydration conditions. Dehydration of Ba–MAP at 140–180 °C induces the formation of a new phase that is restored to the original one upon rehydration. However, above this temperature range the new phase is formed irreversibly. The results indicate that the unusual reversibility and irreversibility of MAP zeolites are related to the cation-dominant media, because some cations act as a precursor for obtaining different natural zeolites whose frameworks are different from the GIS framework.

Anthelmintic Activity In Vivo of Epiisopiloturine against Juvenile and Adult Worms of Schistosoma mansoni

Schistosomiasis is a serious disease currently estimated to affect more that 207 million people worldwide. Due to the intensive use of praziquantel, there is increasing concern about the development of drug-resistant strains. Therefore, it is necessary to search for and investigate new potential schistosomicidal compounds. This work reports the in vivo effect of the alkaloid epiisopiloturine (EPI) against adults and juvenile worms of Schistosoma mansoni. EPI was first purified its thermal behavior and theoretical solubility parameters charaterised. In the experiment, mice were treated with EPI over the 21 days post-infection with the doses of 40 and 200 mg/kg, and 45 days post-infection with single doses of 40, 100 and 300 mg/kg. The treatment with EPI at 40 mg/kg was more effective in adult worms when compared with doses of 100 and 300 mg/kg. The treatment with 40 mg/kg in adult worms reduced parasite burden significantly, lead to reduction in hepatosplenomegaly, reduced the egg burden in faeces, and decreased granuloma diameter. Scanning electron microscopy revealed morphological changes to the parasite tegument after treatment, including the loss of important features. Additionally, the in vivo treatment against juvenile with 40 mg/kg showed a reduction of the total worm burden of 50.2%. Histopathological studies were performed on liver, spleen, lung, kidney and brain and EPI was shown to have a DL50 of 8000 mg/kg. Therefore EPI shows potential to be used in schistosomiasis treatment. This is the first time that schistosomicidal in vivo activity of EPI has been reported.