In this work, some of the synthesis methods already reported for aluminum(III) hydroxide polymorphs with layered structure like gibbsite are revisited. Gibbsite was synthesized with high purity and yield by a simple route developed from modifications of a heating method proposed in the literature, making it possible to prepare gibbsite in regular glassware, avoiding the use of hydrothermal reactor and oven, as described in the literature. The proposed synthesis was conducted with a heating system under reflux conditions in a glass heating flask, using an oil bath, without the need for more sophisticated equipment. This is an accessible alternative method for crystalline gibbsite synthesis, with yield (76 wt.%). The obtained gibbsite was used as a precursor for the synthesis of a lithium/aluminum layered double hydroxide (LDH) from the intercalation method of Al(OH)3 in aqueous solution of lithium chloride. Gibbsite and the obtained LDH Li/Al were used for the immobilization of an anionic porphyrin with a loading on the order of 10-5 mol g-1 of solid, thus being alternative solid supports for catalytic species such as porphyrins.

The synthetic versatility and the potential applications of porphyrins and analogues in different fields have aroused special interest in their study, especially to mimic biological systems, such as cytochrome P-450. The ability of the porphyrin tetrapyrrolic core to accommodate metal ions of varying charges can modulate the type of application of these compounds. As a contribution, in this special number in honor to the Brazilian women who have devoted their lives to the growth and dissemination of chemistry knowledge, we report the advances in porphyrin research in Brazil for catalytic purposes and other applications, beginning at the Universidade de São Paulo (USP) at Ribeirão Preto. We also discuss some works that have resulted from joint research effort between Brazilian researchers and Portuguese colleagues from the Universidade de Aveiro, Portugal, working in the porphyrin field.

The present article describes the development of the Inorganic Chemistry in Brazil in the last 15 years, using as starting point the scientific contributions of a group of 405 researchers selected among the members of the Inorganic Chemistry Division of the Brazilian Chemical Society (SBQ), and active participants of both SBQ Annual Meetings and Brazilian Meetings on Inorganic Chemistry. A total of 3006 articles, representative of the Brazilian scientific production on Inorganic Chemistry from 2002 to January 2017, was analyzed. Among the various aspects evaluated are: prevalent research topics, production impact, geographic distribution within Brazil, international collaborations, and human resource background, development, and perspectives. The evolution of the Inorganic Chemistry production in Brazil in the last 15 years was analyzed considering the concurrent expansion of Brazilian graduate and post-graduate educational system along with availability of funding resources. Information from sources such as CAPES, Sucupira database, eMEC, Web of Science, and CNPq, complemented the scientific production data gathered from the Curriculum Vitae (Lattes Curriculum database) of the 405 representative inorganic chemistry researchers. The present analysis expands the previous 1977-2001 study by Toma, Ferreira, and Serra (Quim. Nova 2002, 25, 66), depicting, thus, a 40-year scenery of Inorganic Chemistry in Brazil, which overlaps with the period of activity of SBQ.

A oxidação de substratos orgânicos é uma importante classe de reações explorada visando a produção de insumos industriais tais como epóxidos, álcoois e cetonas. As metaloporfirinas são compostos com reconhecida atividade catalítica que mimetizam processos de oxidação que ocorrem em seres vivos. A sua imobilização em diferentes sólidos robustos e inertes permite a recuperação e reuso do catalisador em processos catalíticos heterogêneos. Hidróxidos duplos lamelares (LDHs) são materiais inorgânicos constituídos de hidróxidos de metais di e trivalentes, resultando em lamelas bidimensionais carregadas positivamente. Neste trabalho reportamos a preparação de catalisadores baseados na imobilização de ferroporfirina (FeP) em LDH macroporoso (LDHM) obtido pelo método de co-precipitação usando poliestireno como template, reconstrução de óxidos e esfoliação (LDHME). A imobilização da FeP no LDH intercalado com ânions nitrato obtido pelo método de co-precipitação também é reportada. Os sólidos obtidos foram caracterizados e investigados como catalisadores na oxidação do cicloocteno e cicloexano.

The oxidation of organic substrates via catalytic routes is an important class of reactions to produce industrial input materials such as epoxides, alcohols, and ketones. Metalloporphyrins display recognized catalytic activity that mimics oxidation processes in living organisms. Their immobilization in different inert supports allows their recovery and reuse in heterogeneous catalytic processes. Layered double hydroxides (LDHs) are inorganic materials consisting of di- and trivalent metal hydroxides that afford bidimensional positively charged layers. This work reports on the preparation of the solid based on macroporous LDHs (LDHMs) by the co-precipitation method, which involved the use of polystyrene as template, oxides reconstruction, and exfoliation, to furnish LDHME. We also describe the immobilization of an iron(III) porphyrin (FeP) in LDHME and in LDH intercalated with nitrate anions, obtained by the co-precipitation method. Application of the immobilized catalysts in (Z)-cyclooctene and cyclohexane oxidation will help to assess their catalytic activity.

Sodium bismuthate dihydrate and two species derived from its thermal treatment were investigated as catalysts for soybean oil methanolysis and, regardless of the type of solid used, ester yields always above 76 wt% were obtained. After a single reaction course, both liquid and solid phases were characterized using several analytical methods such as X-ray diffraction and thermogravimetric analysis. As a result, the catalytic phenomenon was shown to be solely due to the leaching of alkalinecatalytic species from the solid materials.

Este trabalho relata a síntese e a caracterização dos complexos de manganês(II) [MnII(Hbpeten)] e [MnII(Hbnbpeten)], respectivamente [N,N'-bis-(2-hidroxibenzil)-N-(2-piridilmetil)-N'-(2-hidroxietil)etano-1,2-diamine]manganês(II) e [N,N'-bis-(5-nitro-2-hidroxibenzil)-N'-(2-hidroxietil)etano-1,2-diamin]manganês(II), por análise elementar, voltametria cíclica, espectroscopias eletrônica (UV-Vis) e vibracional (FTIR), ressonância magnética nuclear de hidrogênio (¹H NMR) e espectroeletroquímica de ressonância paramagnética eletrônica (EPR). Os dados de espectroeletroquímica de EPR foram consistentes com a redução de um grupo nitro, tanto no H3bnbpeten livre quanto no complexo de manganês. Além disso, os cálculos teóricos foram consistentes com os resultados experimentais, mostrando que somente um grupo nitro contribui para a formação dos orbitais LUMO e sugerindo que os resultados teóricos são adequados para explicar as propriedades eletrônicas dos complexos.

The synthesis and characterization of the manganese(II) complexes [MnII(Hbpeten)] and [MnII(Hbnbpeten)], where H3bpeten and H3bnbpeten are respectively [N,N'-bis-(2-hydroxybenzyl)-N-(2-pyridylmethyl)-N'-(2-hydroxyethyl)ethane-1,2-diamine] and [N,N'-bis-(5-nitro-2-hydroxybenzyl)-N'-(2-hydroxyethyl)ethane-1,2-diamine], are reported. The characterization was carried out by elemental analyses, cyclic voltammetry, spectroscopic methods (UV-Vis, FTIR, ¹H NMR), electronic paramagnetic resonance spectroelectrochemistry (EPR) and theoretical DFT calculations. The electrochemistry and EPR espectroelectrochemistry data were consistent with the reduction of one of the nitro groups in free H3bnbpeten and in the respective manganese(II) complex. These results were supported by DFT calculations, which showed that only one nitro group contributes to the LUMO. The theoretical data appear to be suitable to describe the electronic properties of the compounds.

Catalisadores sólidos foram preparados pela interação de ferroporfirinas com sílica obtida pelo processo sol-gel. A presença da ferroporfirina na matriz de sílica e a morfologia das partículas obtidas foram estudadas por espectroscopia eletrônica na região do ultravioleta e visível, difratometria de raios X de pó, espectroscopia vibracional na região do infravermelho, microscopia eletrônica de transmissão, ressonância paramagnética eletrônica e análises termogravimétricas. A atividade catalítica dos sólidos obtidos foi investigada frente a oxidação dos substratos (Z)-cicloocteno, cicloexeno e cicloexano por iodosilbenzeno em meio de diclorometano e acetonitrila. Os resultados catalíticos obtidos foram comparáveis àqueles observados quando as ferroporfirinas em solução (catálise homogênea) foram utilizadas.

Solid catalysts have been prepared by chemical interaction of iron(III) porphyrins with the surface of the pores of a silica matrix obtained by the sol-gel method. The presence of the complexes in the silica matrix and the morphology of the obtained particles were studied by UV-Vis spectroscopy, powder X-ray diffractometry, infrared spectroscopy, transmission electron microscopy, electron paramagnetic resonance and thermogravimetric analysis. The catalytic activity of the immobilized iron(III) porphyrins in the oxidation of (Z)-cyclooctene, cyclohexene and cyclohexane was evaluated in dichloromethane/acetonitrile 1:1 solvent mixture (v/v) using iodosylbenzene as oxidant. Results were compared with those achieved with the homogeneous counterparts.

Glass ionomer cements are widely employed in dentistry due to their physical, biological and mainly anti-caries properties. Glass ionomers consist of an aluminosilicate glass matrix modified with other elements, and they contain large quantities of fluorine. In this study, we report on the preparation of calcium-fluoroaluminosilicate glasses by a nonhydrolytic sol-gel route as an alternative approach to obtaining alumina-silica matrices. The glass powders were prepared via the non-hydrolytic sol-gel method, by mixing AlCl3, SiCl4, CaF2, AlF3, NaF, and AlPO4. The powders were studied by thermal analysis (TG/DTA/DSC), photoluminescence (PL), nuclear magnetic resonance (NMR27Al-29Si), and X ray diffraction (XRD). TG/DTA/DSC analyses revealed a constant mass loss due to structural changes during the heating process, which was confirmed by NMR and PL. A stable aluminosilicate matrix with potential future application as a glass ionomer base was obtained.

The development of an array of chemically-responsive dyes on a porous membrane and in its use as a general sensor for odors and volatile organic compounds (VOCs) is reviewed. These colorimetric sensor arrays (CSA) act as an "optoelectronic nose" by using an array of multiple dyes whose color changes are based on the full range of intermolecular interactions. The CSA is digitally imaged before and after exposure and the resulting difference map provides a digital fingerprint for any VOC or mixture of odorants. The result is an enormous increase in discriminatory power among odorants compared to prior electronic nose technologies. For the detection of biologically important analytes, including amines, carboxylic acids, and thiols, high sensitivities (ppbv) have been demonstrated. The array is essentially non-responsive to changes in humidity due to the hydrophobicity of the dyes and membrane.

Crisotila natural e quimicamente modificada foi usada como matrizes para imobilização de ferroporfirinas de segunda geração. As atividades catalíticas dos sólidos obtidos foram avaliadas em reações de oxidação de cicloexano, usando iodosilbenzeno como oxidante. Os resultados de catálise foram analisados e comparados aos obtidos pela imobilização das mesmas ferroporfirinas em sílica funcionalizada com 3-APTS, derivadas do tratamento ácido da crisotila. Os resultados preliminares mostraram que os catalisadores são eficientes e seletivos para a obtenção de álcool.

Natural and grafted chrysotile were used as matrices for the immobilization of second generation iron porphyrins. The catalysts obtained were evaluated in the oxidation reaction of cyclohexane, using iodosylbenzene as oxidant agent. The catalyst activity for different conditions was compared with results for the same porphyrins immobilized with 3-APTS grafted disordered silica, obtained from acid-leached chrysotile. Preliminary results have shown that high activity can be obtained with short reaction times, and that the reaction is specific for alcohol.

This review presents studies on methyl coenzyme M reductase, the biological system Factor 430 (F430) and the use of nickel(II) complexes as structural and functional models. The ability of F430 and nickel(II) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the CH3-S bond cleavage of methyl CoM (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system F430 was reviewed. The importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed.