Two series of allyl sulfonamides, prepared from Morita-Baylis-Hillman adducts and primary aromatic sulfonamides, were fully characterized. The Z configuration for the products derived from 2-[hydroxy(phenyl)methyl]acrylonitrile (1) and E configuration for those derived from methyl 2-[hydroxy(phenyl)methyl]acrylate (2) were confirmed by X-ray diffraction for one compound of each series (1e, 2f). Density functional theory calculations for all allyl sulfonamides agreed with the X-ray crystallographic data. X-ray diffraction studies indicate that these compounds form dimers in their crystal structures. Fingerprint plots show that compound 1e is stabilized by H⋯H, C⋯H/H⋯C, O⋯H/H⋯O and N⋯H/H⋯N interactions, while the compound 2f has no N⋯H/H⋯N contacts. Hirshfeld surface analyses were performed to gain insight into the behavior of these interactions. Calculated frontier orbitals showed that their highest occupied and lowest unoccupied molecular orbitals are antibonding orbitals. The allyl sulfonamides 1e and 2f are among the most active compounds in each series, inhibiting approximately 60% of the mycelial growth of Botrytiscinerea at 3 mmol L-1.

Resumo O objetivo deste trabalho foi investigar as propriedades magnéticas e a dependência da condutividade elétrica com a temperatura associada ao modelo de barreiras de potencial entre os cristalitos. A cerâmica de espinélio de gálio e magnésio possui baixa coercividade magnética e alta resistividade elétrica. As amostras de MgGa2-xFexO4 (x= 0,01, 0,05, 0,15, 0,25, 0,35) foram preparadas pelo método de estado sólido e sinterizada a 800 °C durante 8 h. A análise de difração de raio X confirmou a formação de única fase com estrutura de espinélio cúbico compacto. As medições magnéticas mostraram que a magnetização de saturação e remanescência de todas as amostras aumentaram com a concentração de ferro. O campo coercitivo diminuiu até a concentração x= 0,15 e acima de x= 0,25 observou-se um aumento no campo coercivo. Através da caracterização eléctrica verificou-se que as amostras apresentaram comportamento isolante para x= 0,01 e acima de x= 0,15 observou-se um comportamento semicondutor compatível com o modelo de barreira de potencial entre cristalitos, ou seja, preenche a condição de L/2 > LD (tamanho de cristalito L em comparação com o comprimento de Debye) e a condução é limitada por barreiras de potencial entre os cristalitos.

Abstract The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa2-xFexO4 samples (x= 0.01, 0.05, 0.15, 0.25, 0.35) were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > LD (crystallite size L in comparison with the Debye length LD), and the conduction is limited by potential barriers between the crystallites.

This paper describes the synthesis of four new organotin compounds of general formula: (Ph4P)[Sn(Cy)3(RSO2N=CS2)] [Ph4P = tetraphenylphosphonium cation, Cy = cyclohexyl, R = C6H5 (1), 4-ClC6H4 (2), 4-BrC6H4 (3) and 4-IC6H4 (4)]. They were obtained by the reaction between four different potassium N-R-sulfonyldithiocarbimate salts and tricyclohexyltin chloride in methanol, and were isolated as tetraphenylphosphonium salts. The elemental analyses of C, H, N and the data of high-resolution mass spectrometry were consistent with the proposed formulae. The 119Sn NMR spectra and 119Sn Mössbauer spectroscopic data were consistent with the presence of tetracoordinated tin(IV) species in solution and in the solid state. The electrolytic molar conductance and the integration curves in the 1H NMR spectra are in accord with the 1:1 proportion between the tetraphenylphosphonium cations and the complex anions. The activity of the new compounds in the vulcanization of nitrile rubber was evaluated and the results were compared to those achieved with the commercial accelerators: N-tert-butyl-2-benzothiazolesulfenamide (TBBS), tetramethylthiuram disulfide (TMTD) and zinc diethyldithiocarbamate (ZEDC).

Six new salts of organometallic complexes of tin(IV) with the general formulae: (Ph4P)2[Sn(Bu)2(RSO2N=CS2)2] and [Fe(phen)3][Sn(Bu)2(RSO2N=CS2)2] [Ph4P = tetraphenylphosphonium, R = CH3 (1), C2H5 (2) and C4H9 (3); Fe(phen)3 = tris(1,10-phenanthroline)iron(II), R = CH3 (4), C2H5 (5) and C4H9 (6)] were synthetized from potassium dithiocarbimates (RSO2N=CS2K2.H2O) in reaction with dichlorobis-n-butyltin(IV) and tetraphenylphosphonium chloride (1-3) in N,N-dimethylformamide or tris(1,10-phenanthroline)iron(II) (4-6) in methanol. The new compounds were characterized by elemental analysis of Fe and Sn, and by vibrational, Mössbauer and nuclear magnetic resonance of 1H, 13C and 119Sn spectroscopies. High-resolution mass spectra in the negative and positive modes were also obtained. The elemental analyses and the exact masses obtained for the cations and the complex anions were consistent with the proposed formulae. The Mössbauer spectroscopic data were consistent with the presence of tin(IV) with coordination numbers between 4 and 5 (compounds 1-6), and of hexacoordinated iron(II) (compounds 4-6). The 1H and 13C NMR spectra presented all the expected signals for the cations and anions, and the signals observed in the 119Sn NMR spectra indicated an equilibrium between tetra- and pentacoordination around the tin atoms in solution. The in vitro activity of the new compounds was evaluated against Botrytis cinerea and Colletotrichum acutatum.

<p>Botrytis blight or gray mold is a highly destructive disease caused by <italic>Botrytis</italic> spp., that infects flowers, trees vegetables, fruit, especially grapevines and strawberry. Three new compounds with general formula (A)₂[Zn(4-FC₆H₄SO₂N=CS₂)₂], where A = PPh₃CH₃ (<bold>2a</bold>), PPh₃C₂H₅ (<bold>2b</bold>), PPh₃C₄H₉ (<bold>2c</bold>), and the previously published compounds where A = PPh₄ (<bold>2d</bold>) and NBu₄ (<bold>2e</bold>), were synthesized by the reaction of 4-fluorophenylsulfonyldithiocarbimate potassium dihydrate and zinc(II) acetate dihydrate with the appropriate counter cations (A) halides. The new compounds were characterized by infrared, ¹H and ¹³C NMR spectroscopies. All these salts inhibited the growth of <italic>Botrytis cinerea</italic>, with compounds <bold>2c</bold> and <bold>2d</bold> showing greater antifungal activity than zinc dimethyldithiocarbamate, the active principle of the fungicide Ziram. The bis(dithiocarbimate)zincate(II) salts are also active against the bacteria <italic>Escherichia coli</italic> and <italic>Staphylococcus aureus</italic>.</p>

Four new compounds with the general formula [Fe(phen)3][Zn(RSO2N=CS2)2], where phen = 1,10-phenanthroline, R = 4-FC6H4 (1), 4-ClC6H4 (2), 4-BrC6H4 (3) and 4-IC6H4 (4), respectively, were obtained by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate (RSO2N=CS2K2) and tris(1,10-phenanthroline)iron(II) sulfate, with zinc(II) acetate dihydrate in dimethylformamide. The elemental analyses and the IR data were consistent with the formation of the expected complexes salts. The ¹H and 13C NMR spectra showed the signals for the cationic iron(II) complex and dithiocarbimate moieties. The molar conductance data were consistent with the 1:1 cation:anion complexes in 1-4. The antifungal activities of the compounds were tested in vitro against Candida albicans, Candida tropicalis and Colletotrichum gloeosporioides.

O ZNIBU, acelerador de caráter lento foi avaliado neste trabalho em composições de polibutadieno. Este acelerador foi sintetizado com o objetivo de substituir, ou reduzir, o uso de alguns aceleradores comerciais muito utilizados em composições elastoméricas mas que, por serem formadores de nitrosaminas, podem ser prejudiciais à saúde. A fim de corrigir o caráter de acelerador lento do ZNIBU, este composto foi utilizado em conjunto com o acelerador comercial CBS (N-ciclohexil-2-benzotiazol-2-sulfenamida). Foi observado que pequenas quantidades dos dois aceleradores não são efetivas na aceleração da vulcanização nas composições do tipo goma pura. No entanto a presença de negro de fumo exerce um efeito positivo sobre a velocidade. As propriedades mecânicas estudadas mostram que o ZNIBU aumenta a resistência à tração da goma pura (35%), em comparação com a composição similar vulcanizada com CBS e, na presença do negro de fumo, este aumento é ainda mais expressivo (175%). Quanto à resistência ao rasgamento, a vulcanização com o ZNIBU forneceu o mais baixo valor da propriedade para a goma pura, enquanto que a composição com negro de fumo apresentou o mais alto valor.

ZNIBU, a slow accelerator, was evaluated in polybutadiene compositions. This accelerator was synthesized intending to replace or reduce the use of some very used commercial accelerators in rubber compositions which, due to their nitrosamine-forming potential, can be harmful to health. In order to correct for the slow accelerating character ZNIBU was used in combination with the commercial accelerator CBS (N-cyclohexyl-2-benzothiazole-2-sulfenamide). It was observed that small amounts of the accelerators are not effective in the vulcanization accelerating process of gum type compositions. Nevertheless, the presence of carbon black exerts a positive effect on the reaction rate. The investigated mechanical properties show that ZNIBU improves stress strength of the pure gum (35%), when compared with a similar composition vulcanized with CBS and, in the presence of carbon black, the increase is even more expressive (175%). As for the tear strength, the ZNIBU vulcanization provided the lowest value for the pure gum composition while the carbon black-filled composition presented the highest value for this property.

O efeito do tipo de acelerador no processo de vulcanização de compostos de borracha nitrílica com dois teores de acrilonitrila foi investigado. Dois aceleradores comerciais, dissulfeto de 2,2'-dibenzotiazol (MBTS) e bis (dimetilditiocarbamato) de zinco (ZDMC), de grupos químicos diferentes, tiazol e ditiocarbamato, respectivamente, foram selecionados e comparados com o composto bis (4 metilfenilsulfonilditiocarbimato-)zincato (II) de tetrabutilamônio (ZNIBU). Os resultados mostram que o tipo de acelerador não só afeta as características de cura, como também tem grande influência nas propriedades físicas. Entre os aceleradores estudados, MBTS foi o menos adequado para a formulação utilizada. Surpreendentemente, verificou-se que o ZNIBU mostrou comportamento intermediário, sendo mais eficaz do que o MBTS e menos eficiente que o ZDMC, considerado um ultra-acelerador, em relação ao tempo ótimo de vulcanização.

The effect of the type of accelerator on the vulcanization process of nitrile rubber compounds with two acrilonitrile amounts was investigated. Two commercial accelerators benzothiazole (MBTS) and zinc dimethyldithiocarbamate (ZDMC), from different chemical groups, thiazole and dithiocarbamate, respectively, were selected and compared with the compound bis (4 methylphenylsulfonyldithiocarbimato-)zincate (II) of tetrabutylammoniun (ZNIBU). The results show that the type of accelerator not only affects the cure characteristics, but also has great influence on the physical properties. Among the accelerators studied, MBTS was found to be the least adequate for the formulation used as far as rheometric parameters are concerned. Surprisingly, it was found that ZNIBU showed an intermediate behavior, being more efficient than MBTS but not as much as ZDMC, considered an ultra accelerator, as for the optimum cure time.

Neste trabalho a substância ZNIBU [bis(4-metilfenilditiocarbimato)zincato(II) de tetrabutilamônio] foi usada em formulações de borracha natural (NR) e o seu efeito como acelerador de vulcanização foi investigado. As composições, vulcanizadas com a substância em questão, foram submetidas a testes mecânicos e os resultados comparados com os de outras composições vulcanizadas com os aceleradores comerciais CBS (N-ciclohexil-2-benzotiazol-2-sulfenamida), TMTD (dissulfeto de tetrametiltiuram) e MBTS (dissulfeto de benzotiazol). Propriedades como dureza, resiliência e densidade foram avaliadas em presença ou não da carga negro de fumo.

The acceleration potential of ZNIBU [tetrabutyl ammonium bis(4-methylphenyldithiocarbimatozincate(II))] in the vulcanization process of natural rubber compounds was investigated. The vulcanized compounds were tested for hardness, resilience and density and compared with those vulcanized with commercial accelerators such as CBS (N-cyclohexyl-2-benzothiazolesulphenamide), TMTD (tetramethyl thiuram disulphide) and MBTS (dibenzothiazole disulphide). The new accelerator tested was found to be too slow for a commercial application, but its properties were similar to those of other accelerators.

We investigated the effect of adding the field-dependent recombination process, namely field-enhanced trapping, to the generation-recombination processes of charge carriers that model current oscillations in semiconductors. The main new features arising from this modification are identified in bifurcation diagrams with the electric field as the control parameter. The characteristic of the bifurcation diagrams is a function of impurity energy. Thus, we generated a set of bifurcation diagrams for a range of the impurity energy and applied bias. The energy dependence of the bifurcation diagrams is discussed considering the context of the competition between the generation-recombination mechanisms impact ionization and field-enhanced trapping.

We present an experimental study of bifurcation diagrams from low frequency current oscillations (LFO) measurements obtained from semi-insulating GaAs samples grown by low temperature molecular beam Epitaxy (LT-MBE). The considered growth temperatures were 215ºC and 265ºC. LFO are considered to be spontaneously generated oscillations under constant applied bias V. These oscillations were measurement and recorded in the form of time series. The bifurcation diagrams were obtained from the sequence of minima as a function of the applied bias. The standard measurement procedure was described elsewhere. As the control parameter, the bias allows the identification of a bifurcation route to chaos.

Electric transport properties measured by Van der Pauw resistivity experiments of Low-Temperature Molecular Beam Epitaxy (LT-MBE) GaAs samples are used to identify a method to improve the resistivity of GaAs material. We present results on five samples grown at 265, 310, 315, 325, and 345 ºC. The electric measurements were carried out at temperatures ranging from 130 to 300 K. In this temperature range the dominant transport process is identified as variable range hopping. The hopping parameter plotted against the growth temperature is shown to present a maximum. The mechanisms responsible for this behavior are discussed in relation to the compensation ratio.

Polyaniline (PANI) and their charge transfer complexes are engineering materials that continue to attract considerable attention from engineers due to their unique electrochemical behavior, environmental stability and high degree of processability. Extensive works on the preparation of electrically conductive PANI blends containing a polymeric matrix having desirable physical and good mechanical characteristics have pointed as a promising route to overcome the PANI intractabilities. This paper reports the electrical properties of the dichromated PANI/poly(vinyl alcohol) (PANI:Cr3+/PVA) blends. Doped polyaniline powder in the emeraldine base form was synthesized by the classical chemical oxidation of aniline with ammonium persulfate as the oxidant in the presence of chromium (Cr3+). The SEM (Phillips XL 30) was used to understand the changes occurring in the conductivity to a microstructure level. The distribution of PANI:Cr3+ (50% w/w) in the host polymer (PVA) show some tendency to occur in "flocculated structures". The samples were cut into circular shapes to form films about 500 microns thick. Electrical contacts were made by sputtering gold over sample surfaces. We have carried out impedance spectroscopy measurements in the range of 20Hz to 1MHz. Measurements carried at 100K and 250K indicates that thermally activated carrier process between PANI:Cr3+ grains in the PANI:Cr3+/PVA blend sample are responsible for its high temperature conductivity.

O ácido 6alfa,7beta-di-hidroxivouacapan-17beta-óico (1) e o 6alfa,7beta-di-hidroxivouacapan-17beta-oato de metila (2) são produtos naturais isolados do extrato hexânico de frutos de Pterodon polygalaeflorus Benth. Este trabalho descreve a preparação e caracterização por espectroscopias no infravermelho, de ressonância magnética nuclear e por análise elementar do derivado inédito 6alfa,7beta-tiocarbonildioxivouacapan-17beta-oato de metila (5), a partir do éster 2. A estrutura do composto 5 foi determinada por difração de raios-X. Na concentração de 100 ppm, este composto inibiu o crescimento radicular de Sorgum bicolor L. (-28%) e não mostrou efeitos significantes sobre Cucumis sativus L..

The 6alpha,7beta-dihydroxyvouacapan-17beta-oic acid (1) and methyl 6alpha,7beta-dihydroxyvouacapan-17beta-oate (2) are natural products isolated from the hexane extract of Pterodon polygalaeflorus Benth fruits. Here we describe the preparation and characterization by infrared and nuclear magnetic resonance spectroscopy, and by elemental analysis of the novel derivative methyl 6alpha,7beta-thiocarbonyldioxyvouacapan-17beta-oate (5), from the ester 2. The structure of compound 5 was determined by X-ray diffraction. At the concentration of 100 ppm, this compound inhibited the radicle growth of Sorgum bicolor L. (-28%) and showed no significant effect on Cucumis sativus L..

We have observed Low Frequency Oscillations (LFO) in a GaAs sample grown by molecular beam epitaxy (MBE) at 300 °C as a function of applied electric field, temperature and illumination intensity. Time series of the oscillations for different values of the applied electric field at room temperature were obtained. We have also obtained the jxE characteristics as a function of temperature and light intensity. We were able to control the LFO using three experimental parameters, the electrical field, which controls the oscillation frequency, and the temperature and illumination intensity, which control the carrier density and field-enhanced trapping. We were able to identify the LFO dependence on the carrier density and on the field-enhanced trapping.