Determinação do estado fundamental de compostos antiferromagnéticos da série Tb(1-x)Y(x)RhIn(5): aproximação teórico experimental

We present the results of electrical resistivity, magnetic susceptibility, specific heat and x-ray absorption spectroscopy measurements in Tb1−xYxRhIn5 (x = 0.00, 0.15, 0.4.0, 0.50 e 0.70) single crystals. Tb1−xYxRhIn5 is an antiferromagnetic AFM compound with ordering temperature TN ≈ 46 K, the higher TN within the RRhIn5 serie (R : rare earth). We evaluate the physical properties evolution and the supression of the AFM state considering doping and Crystalline Electric Field (CEF) effects on magnetic exchange interaction between Tb3+ magnetic ions. CEF acts like a perturbation potential, breaking the (2J + 1) multiplet s degeneracy. Also, we studied linear-polarization-dependent soft x-ray absorption at Tb M4 and M5 edges to validate X-ray Absorption Spectroscopy as a complementary technique in determining the rare earth CEF ground state. Samples were grown by the indium excess flux and the experimental data (magnetic susceptibility and specific heat) were adjusted with a mean field model that takes account magnetic exchange interaction between first neighbors and CEF effects. XAS experiments were carried on Total Electron Yield mode at Laborat´onio Nacional de Luz S´ıncrotron, Campinas. We measured X-ray absorption at Tb M4,5 edges with incident polarized X-ray beam parallel and perpendicular to c-axis (E || c e E ⊥ c). The mean field model simulates the mean behavior of the whole system and, due to many independent parameters, gives a non unique CEF scheme. XAS is site- and elemental- specific technique and gained the scientific community s attention as complementary technique in determining CEF ground state in rare earth based compounds. In this work we wil discuss the non conclusive results of XAS technique in TbRhIn5 compounds.

Prospecção química e avaliação biológica de Banisteriopsis laevifolia (Malpighiaceae)

The Banisteriopsis genus is widespread in traditional medicine. This work aims to contribute with information about the chemical composition and on the evaluation of the biological activity of the essential oil, the ethanol extract of the leaves and partitions of the Banisteriopsis laevifolia. The phytochemical screeningtest of ethanol extract and partitions of leaves indicated the presence of flavonoids, terpenoids, saponins, phenols and steroids compounds. Nitrogenous compounds, characteristic of some species of this family, were not detected. Flavonoids were the predominant metabolite, with the highest concentrations on the partitions ethyl acetate and n-butanol. The antibacterial activity, antifungal and cytotoxicity of the essetial oil, ethanol extract and partitions were assyed by microdilution broth method (MBM), where the minimum inhibitory concentrations (MIC) were calculated. The ethanol extract and partitions did not inhibit growth against to Gram positive bacteria tested, with MIC less than 400 mg L-1. For the Gram negative bacteria tested, the hexane and hydroethanol partitios were more effective against F. nucleatum bacteria (MIC 100 ug mL-1). The ethanol extract showed antifungal activity with MIC of 31.2 mg L-1. Ethyl acetate and n-butanol partitions showed MIC 187.5 mg L-1 and 93.7 mg L-1, respectively, arousing interest for isolation studies. The antioxidant activity was evaluated by the DPPH free radical method. The ethanolic extract, ethyl acetate and n-butanol partitions were active, since they showed EC50 values (4.53 ug mL-1, 4.07 and 8.39 ug mL-1, respectively), values equivalent to the BHT (7.3 mg L-1). The analysis by HPLC-MS/MS of the most active fractions (ethyl acetate and n-butanol) identified phenolic compounds (flavonols and phenolic acids) which exert recognized biological activity. The GC-MS analysis of the essential oils from leaves collected in two periods studied (dry and wet), showed a small variation in the number of compounds. The major classes identified for the oil collected in the dry period were aliphatic alcohols (23,4%), terpenoids (18.7%), sterols (10.4%) and long-chain alkanes (9.2%) compounds. Terpenoids (26.8%) were the major class for the rain season. The major compounds (3Z) -hexenol, phytol and untriacontano are present in the two seasons but in different amounts (19.4%, 9.8% and 7.5% during the dry season, and 17.0 %, 14.9% and 15.3% in the rainy season, respectively). The essential oil from rainy season was not effective against to the oral bacteria Gram positive and Gram negative tested. However, showed significant antifungal activity with MIC 1000 mg L-1 against Candidas. Thus, the promising results with respect to biological assays of ethanolic extract and partitions from B. laevifolia contributed to the chemical and biological knowledge of the species B. laevifolia.