308 resultados para FREQUÊNCIAS HARMÔNICAS VIBRACIONAIS
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Pós-graduação em Saúde Coletiva - FMB
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Pós-graduação em Saúde Coletiva - FMB
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Pós-graduação em Engenharia Elétrica - FEIS
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Pós-graduação em Engenharia Elétrica - FEIS
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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This paper aims the preparation, characterization and study of luminescence, particularly as for the cerium ion action as activator or sensitizer, in diphenylphosphinate of lanthanum compounds trivalent ions cerium-, europium-, and/or terbium-doped. The following compounds were prepared and studied: i) La1-(x+y)CexEuy(DFF)3; ii) La1-(x+y)CexTby(DFF)3; iii) La1-(x+y+z)CexEuyTbz(DFF)3, with x = 10%, y = 5% e z = 5%. The diphenylphosphinate of lanthanum, Ln[(Ph2)PO2]3, are complexes obtained by the mixture of lanthanides chlorides with diphenylphosphinic acid, ethanol medium. These compounds make white powders, crystalline, insoluble in normal temperature and pressure, and are chemically and thermally stable. When doping with Ce3+, Eu3+ and/or Tb3+, the compounds present characteristic luminescence. Luminescent materials are made of a host matrix incorporated with few amounts of ions called activators, which are able to present luminescence after being excited by UV light or high energy radiation, and sensitizer ions, which have the role of absorbing excitation energy and transfer it to the activator, for it to emit luminescence radiation. The infrared vibrational spectroscopy indicates that the coordination occurs by the oxygens of phosphorile group with ΔνPO of about 40 cm-1 compared to the free ligand. The X Ray difractograms of compounds Eu- and/or Tb-doped are similar, but they present profile of diffraction different observed by Stucchi and col. In previous papers, indicated an influence of Ce in the crystalline phase formation of these matrices. In luminescence spectrums, the excitation that can be made by the levels of ligand in 273 nm, or cerium ion in area between 300 and 400 nm were observed. In the emission spectrum, with excitation in 273 nm, is possible to observe the emission of Ce3+ below 400 nm and the Eu3+ in 592, 611 and 617 nm, and the...as a sensitizer to.
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This work deals with the synthesis, spectroscopic characterization of mono and polynuclear Pd(II) compounds obtained from the reaction between [PdCl2(MeCN)2] precursor and imidazolidine-2-thione (L1) and benzimidazoline-2-thione (L2). The interaction between [PdCl2(MeCN)2] and imidazolidine-2-thione, in the 1:2 molar ratio, using MeOH as solvent, yielded compound [Pd2Cl4(L1)4]Cl2 (1) whereas the complex [Pd2Br4(L1)4]Br2 (2) was obtained from the reaction between 1 and Br- ions. Binuclear compounds of general formulae [Pd2(L2)4]X23/2 MeOH {X= Cl-(3), Br-(4)} were synthesized using benzimidazoline-2-thione as ligand, employing the same procedure used in the synthesis of 1 and 2, respectively. The new complexes 1-4 are crystalline, air stable and soluble in methanol and dmso. The compounds were characterized by elemental analysis, IR spectroscopy, ESI/MS mass spectrometry and thermogravimetry. Coordination of the ligands L1 and L2 via sulphur atom was evidenced by the shift of the CS band (~499 cm-1, 1 and 2; ~620 cm-1, 3 and 4) to lower frequencies in comparison with those found in the free ligands (510 cm-1, L1; 660 cm-1, L2), indicating the weakening of the CS bom after coordination. ESI/EM mass spectra (positive mode) of the complexes 1-4 allowed atribute the molecular formulae [Pd2X4(L1)4]X2 {X= Cl-(1), Br-(2)} and [Pd2(L2)4]X2 {X= Cl-(3), Br-(4)} by the appearance of the peaks at m/z 794,61 [(1) + MeOH]+, m/z 836,77 [(2) - 2H - L1]+, m/z 810 [(3) - 2Cl]+, m/z 810 [(4) - 2Br]+. The TG-DTA curves showed that the complexes 1 and 2 are thermally stable up to 212 and 169º C, respectively, and further decompose to metallic palladium at 527º C (1, obt. 28,46 %; calcd. 27,88%) and 895º C (2, obt. 22,85 %; calcd. 22,62%). Compounds 3 and 4 exhibited an initial mass loss of ~5% between 25 -146º C related to the release of metanol molecules. The complexes 3...Fujimura Leite.
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Pós-graduação em Engenharia Elétrica - FEB
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)