The 1,4-naphthoquinones are an important group of compounds intensively studied because of their wide range of biological activities. Four 2-chloro-3-(substituted-phenylamino)-1,4 naphthoquinone derivatives were synthesized, and the vibrational modes of these molecules were assigned using Raman and Fourier transform infrared spectroscopy (FTIR) techniques. In addition, X-ray studies were performed for one of these derivatives. Density functional theory (DFT) calculations were also developed for these compounds and presented. In summary, the results obtained from these studies can assess chemical changes in the structures of functionalized quinones and the discovery of candidate biologically active compounds.

Lithium manganese oxide, LiMn2O4, was synthesized in two temperature stages, where the first consisted by an ecofriendly solution combustion method at 300 °C. Finally, the as-burned powders were thermal treated at 500 and 700 °C. The structural and morphological changes were evaluated by the Rietveld method and density functional theory (DFT) calculations. The Rietveld refinement indicates obtaining the spinel cubic phase LiMn2O4 and a small amount of Mn2O3. The analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show a porous microstructure composed of nano-sized crystallites for the sample treated at 500 °C. In cyclic voltammetry, it was possible to observe that the reduction-oxidation reaction is reversible due to the shape of voltammograms and the anodic and cathodic peaks of Mn ions. The theoretical calculations considered the experimental crystallographic parameters. The unit cell volume change was evaluated according to distinct amounts of lithium ions in the structure. The removal of the Li+ cations from the oxides promotes a volume contraction. Therefore, it was possible to evaluate the participation of the Mn3+ ions in the frontier region between the valence and conduction bands. The density of states (DOS) calculation shows a predominant contribution of the O 2p and Mn 3d orbitals in the frontier orbitals.

Density functional theory (DFT) (B3LYP/6-311++G(d,p)) calculations of the interacting strength 1,2-dithiolene anionic ligands with the [M(OH2)4]2+ and [M(OH2)2]2+ complexes (M = Ni and Zn) were performed. Three series of ligands were studied: compounds with an aromatic ring, with an ethylene moiety and with a heterocyclic ring. The ligands have substituents electron donors and acceptors by induction and resonance. Two substitution reactions were studied: the first is the substitution of two water molecules from the [M(OH2)6]2+ by a dithiolene anionic ligand (L2-) and the second is the substitution of two water molecules from the [M(OH2)4L] by another dithiolene anionic ligand. Geometric, electronic and energetic properties of the substituted aquacations are correlated with the metal-ligand affinity. All the substitution processes for both metal cations are spontaneous and are modulated by the electronic effect of each substituent of the ligand. Geometric parameters and chelation angle are correlated with the interaction strength. The energy decomposition analysis (EDA) results show that the electrostatic component is the main stabilizing term for the monosubstituted complexes, while for the disubstituted complexes the covalent term is the main stabilizing component. The polarization term is the main one to describe the covalent character. Natural bond orbital (NBO) shows the acid-base interaction nature of the metal-ligand bond.

Lithium cobalt oxide, LiCoO2, widely used as cathode in lithium ion batteries was synthesized and their structural and electronic properties investigated. The crystalline powders were prepared by the sol-gel method with four complexing agents: citric acid, glycine, starch and gelatin. These syntheses were compared with the blank test (without complexing agent). The X-ray diffraction and vibrational spectroscopy allowed the identification of the rhombohedral phase LiCoO2 (R3m) as the only or principal crystalline component in all samples. A small fraction of a second phase of cubic spinel Co3O4 was observed in the samples of starch, gelatin and the blank test. The Rietveld refinements showed small structural variations, indicating reduced influence of the complexing agents on the synthesis. The theoretical HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap values are in agreement to those estimated by diffuse reflectance spectroscopy (DRS). The scanning electron microscopy (SEM) showed morphological pattern regardless of the complexing agent used, showing an alternative method.

The effect of γ-Al2O3 support on the NO adsorption on Pd4 clusters was investigated by means of density functional theory (DFT) calculations. Pd4 adsorbed on γ-Al2O3 (represented by a Al14O24H6 cluster) changes its preferential geometry from tetrahedral to a distorted planar structure. The alumina support promotes a higher dispersion in the palladium catalyst and reduces the NO adsorption energy to -25.6 kcal mol-1 (computed at B3LYP/LANL2DZ/6-311+G(d)), in close agreement with the experimental value of -27.2 kcal mol-1. On the bare planar Pd4 cluster the NO molecule adsorbs in a bridge arrangement, with adsorption energy of -41.2 kcal mol-1. Adsorption on the tetrahedral Pd4 cluster occur preferentially in an atop mode, with adsorption energy of -30.6 kcal mol-1. Charge density analysis show that the electron flux between the NO molecule and Pd4 depends on the adsorption form, with back-donation being stronger in the bridge adsorption mode.

A desidratação oxidativa do glicerol a ácido acrílico foi estudada com o uso de zeólita Beta impregnada com vanádio. Os catalisadores foram preparados por impregnação úmida do metavanadato de amônio sobre a zeólita Beta na forma amoniacal, seguida de calcinação em ar a 823 K. A impregnação reduziu a área superficial específica, mas não afetou significativamente a acidez (Brønsted e Lewis) da zeólita. A avaliação dos catalisadores foi realizada num reator de leito fixo usando ar como gás de arraste e injetando o glicerol por meio de uma bomba seringa. Acroleína foi o principal produto formado, tendo também sido observados acetaldeído e hidróxi-acetona (acetol). O ácido acrílico foi formado em aproximadamente 25% de seletividade a 548 K sobre as zeólitas impregnadas. O resultado pode ser explicado por análises de XPS (espectroscopia fotoeletrônica de raios X), que mostraram uma boa dispersão de vanádio nos poros da zeólita.

The oxidative dehydration of glycerol to acrylic acid was studied over vanadium-impregnated zeolite Beta. Catalysts were prepared by wet impregnation of ammonium metavanadate over ammonium-exchanged zeolite Beta, followed by air calcination at 823 K. Impregnation reduced the specific surface area, but did not significantly affected the acidity (Brønsted and Lewis) of the zeolites. The catalytic evaluation was carried out in a fixed bed flow reactor using air as the carrier and injecting glycerol by means of a syringe pump. Acrolein was the main product, with acetaldehyde and hydroxy-acetone (acetol) being also formed. Acrylic acid was formed with approximately 25% selectivity at 548 K over the impregnated zeolites. The result can be explained by XPS (X-ray photoelectron spectroscopy) measurements, which indicated a good dispersion of the vanadium inside the pores.

Este trabalho apresenta uma investigação teórico-experimental dos espectros infravermelho/Raman de diversos metais representativos coordenados com 1,3-ditiol-2-tiona-4,5-ditiolato (dmit), a saber [NEt4]2[Zn(dmit)2], [NEt4][Sb(dmit)2] e [NEt4][Bi(dmit)2]. Os espectros IV/Raman de todos os sólidos e também o espectro IV em solução do composto [NEt4]2[Zn(dmit)2] foram registrados de 4000 a 100 cm-1. Duas regiões foram claramente identificadas: abaixo de 380 cm-1 os modos apresentaram forte contribuição metal-ligante, e acima, os modos indicaram majoritária contribuição do ligante. Os espectros IV/Raman do NEt4Br também foram registrados. As bandas vibracionais foram atribuídas a partir da análise de compostos relacionados, de publicações prévias e comparadas com amplo conjunto de cálculos ab initio realizados com diversos ECPs (SBK, Sttutgart), conjunto de bases (com e sem funções d) e metodologias (RHF, DFT e MP2). As geometrias, freqüências e intensidades foram calculadas e comparadas com as freqüências experimentais visando atribuições seguras. Assim, uma excelente concordância foi obtida para diversas bandas experimentais.

This work reports a theoretical-experimental investigation of the infrared/Raman vibrational spectra of several metal 1,3-dithole-2-thione-4,5-dithiolate (dmit) complexes; [NEt4]2[Zn(dmit)2], [NEt4][Sb(dmit)2] and [NEt4][Bi(dmit)2]. IR/Raman spectra of all the solids and the solution IR spectrum of [NEt4]2[Zn(dmit)2] were recorded from 4000 to 100 cm-1. Two regions were clearly identified: below 380 cm-1, the modes presented significant metal-ligand contributions, and above, the modes indicated major ligand contributions. IR/Raman spectra of NEt4Br have also been recorded. The vibrational bands have been assigned starting from the analysis of related compounds, of previous published spectra and compared to several ECPs (SBK, Stuttgart), basis sets (with and without functions d) and methodologies (RHF, MP2 and DFT). Geometries, frequencies and intensities were calculated and compared to the experimental frequencies seeking secure assignment. Thus, an excellent agreement was obtained for several experimental bands.