We reported experimental and theoretical investigation of conformers of 1,2,3-triazole derivatives, substances of exclusively synthetic origin, subject of extensive studies, because of several biological properties, such as antiviral, antimicrobial and antileishmaniasis. We reported molecular/supramolecular X-ray structures of antiophidian compounds I and II. For I and II there are two crystallographic different molecules in the unit cell (A and B). To explore the causes of the similarities in the compound’s crystal structures, intermolecular interactions were explored using the Hirshfeld surface as the fingerprint plots. In addition, density functional theory (DFT) calculations were carried out at the ωB97x-D/6-31G(d,p)-PCM-CHCl3 level aiming to contribute to the interpretation of the experimental data and complement the experimental findings. Two structures named 2A and 5B were found in good agreement with the respective X-ray solid state ones (A and B). Theoretical 1H nuclear magnetic resonance (NMR) spectra calculated for 5B rotated structure (torsion angles deviation around 40° to 90°) was in fine agreement with experimental results (in CDCl3) indicating that the solution molecular structure is considerably different from optimized equilibrium geometries and solid-state structure. Therefore, care is needed when using X-ray structures or DFT geometries to model interaction of drugs with biological targets since significant conformational changes may take place in solution.

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.

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 isoniazid-derived hydrazones 2-pyridinecarbaldehyde- (HPCIH), 2-acetylpyridine- (HAPIH), 2-benzoylpyridine- (HBPIH), 2-pyridineformamide- (HPAmIH) and 2-pyrazineformamide- (HPzAmIH) isonicotinoyl hydrazones, as well as the pyrazinamide-derived thiosemicarbazones 2-pyrazineformamide- (HPzAm4DH), N(4)-methyl-2-pyrazineformamide- (HPzAm4M), N(4)-ethyl-2-pyrazineformamide- (HPzAm4E) and N(4)-phenyl-2-pyrazineformamide- (HPzAm4Ph) thiosemicarbazones, were assayed for their action against intracellular amastigote form of Leishmania (Viannia) braziliensis strains and the glioblastoma multiforme (SF-295), colon adenocarcinoma (HCT-116), ovarian cancer (OVCAR-8) and acute myeloid leukemia (HL-60) human tumor cell lines. All compounds exhibited leishmanicidal effects, with concentrations at which 50% of parasites were inhibited (IC50) in the 10.70-18.84 µM range. Moreover, the compounds were up to 30-fold less toxic to macrophages than to the parasites. Pyrazinamide-derived thiosemicarbazones proved to have poor activity against the tumor cell lines at 5 µg mL-1, whereas, in general the isoniazid-derived hydrazones presented good activity, being HAPIH and HBPIH the most potent compounds (IC50 = 0.42-1.5 µM).

A reação de tert-butil 2-(3-cloro-1,4-dioxo-1,4-di-hidronaftalen-2-ilamino)etilcarbamato com CF3COOH/CH2Cl2 fornece 5-cloro-3,4-di-hidrobenzo[f]quinoxalin-6(2H)-ona. Este composto sofre desidrogenação promovida por ácido na presença de água para dar a 5-clorobenzo[f]quinoxalin-6-ol, inédita. A estrutura molecular no estado sólido, determinada por um estudo de difração de raios X (XRD), e os dados em solução confirmam que a benzoquinoxalina existe na forma do tautômero enol-imina, tanto no estado sólido, quanto em solução, diferentemente de 5-cloro-3,4-di-hidrobenzo[f]quinoxalin-6(2H)-ona que exibe o arranjo ceto-amino. Cálculos de teoria do funcional da densidade (DFT) confirmam a preferência da benzoquinoxalina e dos compostos análogos contendo grupos H ou CH3 no lugar do Cl pela forma enol-imina. Sugere-se que a preferência da benzoquinoxalina pela estrutura enol-imina se deva ao maior caráter aromático desta estrutura em comparação com a forma ceto-amina. Os cálculos DFT dos dois tautômeros das benzo[a]fenazin-5(7H)-onas análogas às benzo[f]quinoxalin-6(4H)-onas indicaram que as estabilidades relativas são dominadas por efeitos de solvatação, no primeiro caso, e pelo grau de aromaticidade no segundo.

The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF3COOH/CH2Cl2 yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH3 groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter.

Neste trabalho nós descrevemos o uso do ultrassom na síntese de novas naftoquinonas, 6a-f e 7a-c, contendo na posição 2 do anel quinonoídico substituintes do tipo aminocarboidratos. Estas substâncias foram preparadas, em condições brandas, através da reação da 1,4-naftoquinona (8a) ou do metoxi-lapachol (8b) com diferentes aminocarboidratos 9a-d. As estruturas das substâncias foram confirmadas através das técnicas de RMN de ¹H e de 13C-APT, uni- e bi-dimensionais (COSY-¹H vs. ¹H e HETCOR ¹J CH), e por espectrometria de massas de alta resolução com ionização por electrospray (ESI MS).

In this report we describe the ultrasound-accelerated synthesis of new naphthoquinone derivatives 6a-f and 7a-c, which possess an aminocarbohydrate chain at the C-2 position of the quinone ring. This novel type of 1,4-naphthoquinone derivative has been synthesized under mild conditions by the reaction of 1,4-naphthoquinone (8a) or methoxylapachol (8b) with different aminocarbohydrates 9a-d. Characterization of all substances was confirmed by one- and two-dimensional nuclear magnetic resonance (NMR) techniques (¹H, 13C-APT, cosy-¹H vs. ¹H and HETCOR ¹J CH) and by high-resolution electrospray ionization mass spectrometry (HR ESI MS).

Dois novos complexos [VO2(L)] e [VO2(HLox)] foram sintetizados e caracterizados por espectroscopias no IV, UV-Vis e RMN, voltametria cíclica, análise elementar e difração de raios X. A síntese do ligante inédito H2Lox também é descrita. Os complexos 1 e 2 foram obtidos pela reação de [VO(acac)2] com os respectivos ligantes HL e H2Lox. Alternativamente, 2 foi preparado a partir da reação de HL com [VO(acac)2] na presença de hidroxilamina, e através da reação de 1 com hidroxilamina. Dados cristalográficos mostram que 1 e 2 apresentam estruturas moleculares similares, onde o centro de vanádio(V) cis-dioxo encontra-se coordenado em um ambiente octaédrico distorcido formado pelos ligantes L- e HLox-, respectivamente. A atividade catalítica destes compostos foi avaliada na oxidação do cicloexano, utilizando H2O2 e t-BuOOH como oxidantes. Ambos apresentam seletividade > 70% para formação de cicloexilidroperóxido. Cálculos B3LYP/6-31G(d) foram empregados na otimização da geometria e para auxiliar na atribuição do espectro eletrônico.

Two novel complexes, [VO2(L)] (1) and [VO2(HLox)] (2), were synthesized and characterized by IV, UV-Vis and NMR spectroscopy, cyclic voltammetry, elemental analysis and X-ray diffraction. The synthesis of a new ligand, H2Lox, is also described. Complexes 1 and 2 were obtained by the reaction of [VO(acac)2] with the ligands HL and H2Lox, respectively. Alternatively, 2 was also obtained by the reaction of HL with [VO(acac)2] in the presence of hydroxylamine, and by the reaction of 1 with hydroxylamine. Crystallographic data show that complexes 1 and 2 have similar molecular structures, in which the cis-dioxovanadium(V) center is coordinated to L- or HLox-, respectively, in a distorted octahedral environment. The catalytic activity of these compounds towards cyclohexane oxidation was evaluated using H2O2 and t-BuOOH as oxidants. Both complexes presented > 70% selectivity for cyclohexylhydroperoxide formation. B3LYP/6-31G(d) calculations were used to confirm the geometry and to help assign the electronic spectra.