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The structure and substitution energies of dichlorotris(triphenylphosphine)ruthenium(II) complex, [RuCl2(PPh3)3], was computed with ten different methods at the density functional theory level usin...

The disease outbreak caused by SARS-CoV-2 continues to rise worldwide, even in countries which have considered it controlled. As new cases appear daily, infecting millions of people and causing thousands of deaths, the current in silico study aims to investigate the imidazolic alkaloids of the species Pilocarpus microphyllus (Jaborandi) as a potential inhibitory activity against the Mpro protease from SARS-CoV-2, since it plays a fundamental role in the processing of polyproteins that are translated from viral RNA. Jaborandi is distributed in some Brazilian biomes, being easily identified, yet little researched, with proven anti-inflammatory, contraceptive, anti-diabetic and gastroprotective activities. In this work, DFT calculation of thermodynamic properties, electrostatic potential surface, frontier molecular orbitals and descriptors of chemical reactivity of imidazolic alkaloids were associated with the use of molecular docking techniques, molecular dynamics and ADMET predictions. One can verify a good reactivity chemistry and energetic stability of epiisopiloturine, epiisopilosine, isopilosine and e pilosine with some residues of amino acids present in the active site of the main protease of COVID-19. In this sense, the results point out to the imidazolic alkaloids of Jaborandi as promising targets for in vitro and in vivo tests, as possible candidates for inhibitors of the enzyme Mpro.

O processo educacional vem passando por grandes transformacoes nas ultimas decadas, como por exemplo, atraves da utilizacao de ferramentas que proporcionam a visualizacao e a reproducao de modelos dinâmicos. Neste sentido, os softwares de simulacao e as ferramentas de modelagem molecular surgem com a finalidade de desenvolverem a compreensao conceitual e minimizarem o aprendizado mecânico dos estudantes no Ensino de Quimica (EQ). A presente pesquisa busca promover uma melhor compreensao de conceitos e calculos sobre os conteudos de Termodinâmica Quimica (TQ), abordados na disciplina de Fisico-Quimica I (FQI) de estudantes do curso de Licenciatura em Quimica da Universidade Estadual do Piaui (UESPI). Nesse sentido, foram produzidos e aplicados tutoriais, a fim de facilitar a utilizacao dos softwares de modelagem molecular pelos graduandos, a partir de aulas praticas computacionais. O metodo de pesquisa empregado e uma abordagem qualitativa do tipo estudo de caso, com a aplicacao de questionarios subjetivos e escalas do tipo Likert de cinco pontos, como instrumentos de coleta de dados. A partir dos resultados pode-se perceber que as utilizacoes dessas ferramentas no ensino contribuem para o aprofundamento do conhecimento termodinâmico, ajudam a estabelecer uma visao mais realistica e simbolica do mundo microscopico, minimizam as limitacoes matematicas na obtencao dos calculos e melhoram o interesse e a motivacao dos estudantes pelo aprendizado.

In this paper, we have applied state-of-the-art technologies and new investigations were developed focusing on obtaining simple and inexpensive molecules for treating cardiovascular diseases, as they are considered the leading cause of death in the world. For the first time, the inclusion complex of sulcatone (SU) and β-cyclodextrin (β-CD) was achieved (using a spray drier) and characterized making use of spectroscopic, thermal and computational methods. In addition, the system was evaluated regarding its vasorelaxant properties. Evidence of the inclusion complex formation was provided using different techniques, such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and 1H nuclear magnetic resonance (NMR) spectroscopies and then deduced by pharmacological experiments, which showed significant changes in relation to the initial material.

We have prepared, by a sol-immobilization method, bimetallic catalysts with different Au:Pt atomic ratios supported on commercial SrCO3. The catalytic performance for the oxidation reaction of benzyl alcohol of such materials was compared to the monometallic counterparts, aiming at the obtaining of the best composition of the material. It was found that the Au:Pt atomic ratio presents a remarkable effect on the system performance, i.e., Pt-rich systems are more selective; however, less active. Thus, an equilibrium related to the activity and selectivity of the system was obtained by considering the yield of the system. Also, some density functional theory (DFT) insights were obtained by using a cluster of 14 atoms of Au and 1 or 2 atoms of Pt. X-ray photoelectron spectroscopy, elemental mapping in scanning transmission electron microscopy before and after catalyst usage, flame atomic absorption spectroscopy, Rietveld refinement, among other techniques, were used and associated to the experimental data, which allowed us to propose a catalytic mechanism for the system, which was important since SrCO3 has not been considered before as catalyst support for alcohol oxidation reactions.

The interaction between pyrenetetrasulphonate (PTS) and methyl viologen (MV 2+ ) leads to a 1:1 charge transfer complex (CTC) in the concentration range below mmol L −1 of the ligands. Quantum mechanical calculations show the 1:1 complex having the planar moiety of PTS and the charges of the sulfonate groups stabilized by the twisted rings of the positively charged MV 2+ species. The peculiar nature of PTS includes high fluorescence quantum yield (~1), clear specular UV–vis spectra and fluorescence emission images, as well similar S 2 ←S 0 and S 3 ←S 0 transitions as those of S 1 ←S 0, all of them exhibiting well resolved vibrational structure. MV 2+ has well known electron-accepting properties that favor the complexation. These features were studied as a function of salt concentration and temperature dependences allowing a detailed comprehension of static and dynamic association processes. Quantum mechanical calculations show the 1:1 stabilization of PTS/MV 2+ . In addition the effect of urea on the CTC equilibrium is presented, as expected the additive acts towards the non-complexed species (solvated free ions). The fluorescence quenching of MV 2+ over PTS highlights is one of the applications of this effect for giant vesicles characterization.

Schistosomiasis is a neglected tropical disease caused by blood flukes of the genus Schistosoma. This disease control has been widely made by praziquantel-reference drug, but resistance to this drug has already been found. There has been the finding of an imidazole alkaloid in jaborandi leaves-epiisopiloturine, which has known activity against adult, young and egg forms of Schistosoma mansoni. This alkaloid is an apolar molecule with difficult solubility; therefore, the liposomal structure of epiisopiloturine was proposed. Liposomes are carrying structures of drugs that may enhance solubility of compounds such as epiisopiloturine. In this work, we report in vitro epiisopiloturine-loaded liposomes effect formed by different concentrations of lipids 9:1 (weight ratio) dipalmitoylphosphatidylcholine:cholesterol and 8:2 (weight ratio) dipalmitoylphosphatidylcholine:cholesterol. Results have showed that epiisopiloturine extraction and isolation have been successful through high-performance liquid chromatography-HPLC and its purity confirmed through mass spectrometry has showed 287 Da molecular mass. Formulations from 9:1 DPPC:cholesterol and 8:2 DPPC:cholesterol with loaded EPI (300 microg/ml) have killed parasites at 100% after incubation 96 h and 120 h, respectively. Confocal microscopy employed to observe morphological alterations in the tegument of adult form of Schistosoma mansoni. Details from interaction, between epiisopiloturine and liposome, have been achieved by semi-empirical AM1 calculations, which have showed that epiisopiloturine inside is more stable than the outside form, at least 10 kcal. This is first time that schistosomicidal activity has been reported for epiisopiloturine-loaded into liposome.

macrocycles was evaluated by the differencebetween the respective binding energies. The first-row metal binding energy is higher to polyethermacrocycle than to polyamine one. In the case of second-row transition metals, the polyamine lig-and has a higher binding energy than the polyether macrocycle. This behavior is in good agreementwith the macrocyclic cavity dimension, which has a direct relation to the ring size and metal ionsize. While the oxygen–oxygen distances are close to4Ainthepolyether macrocycle cavity, in thepolyamine one the nitrogen–nitrogen distances are close to 5 A.

MO calculations were carried out on a cis-[Ru(bpy)2Lx](PF6) 2 complex, where bpy is 2,2'-bipyridine and L is 3-aminopyridine (complex 1 with x = 2), with the Gaussian 03 package using the DFT method. The electronic structure and molecular properties of 1 were characterized in vacuum and in acetonitrile solution, and the results were compared to those obtained from the complex with L = 5,6-bis(3-amidopyridine)-7-oxanorbornene (complex 2 with x = 1). The electronic spectra of 1 and 2 were investigated by TD-DFT. Experimental data from cyclic voltammetry, UV-visible spectroscopy, photochemical and photophysical experiments were compared to the theoretical data to discover the influence of L on the electronic transitions and to interpret the differences between the photochemical behaviors of these complexes. Cálculos de orbitais moleculares para o complexo cis-[Ru(bpy)2Lx](PF6) 2, onde bpy é 2,2'-bipiridina e L é 3-aminopiridina (complexo 1 com x = 2), foram realizados com o programa Gaussian 03 usando o método DFT. A estrutura eletrônica e as propriedades moleculares de 1 foram caracterizadas no vácuo e em solução com acetonitrila e comparadas com os resultados obtidos para o complexo com L = 5,6-bis(3-amidopiridina)-7-oxanorborneno (complexo 2 com x = 1). Os espectros eletrônicos dos complexos 1 e 2 foram investigados por TD-DFT. Os dados experimentais de voltametria cíclica, UV-vis, fotoquímica e fotofísica foram comparados com dados teóricos de maneira a estabelecer a influência de L nas transições eletrônicas e interpretar as diferenças entre os comportamentos fotoquímicos desses complexos.

Hybrid magnetite materials are interesting for both biomedical and catalytic applications due to their well-known biocompatibility, as well as their magnetic and electric properties. In this work we prepared Fe3O4 nanoparticles (NPs) coated with tannic acid (TA), a natural polyphenol, through two different synthetic routes, aiming to understand the influence of TA in the synthesis step and contribute to the development of water-dispersible magnetic materials. The coating process was verified by information obtained from transmission electron microscopy (TEM), zeta-potential and Fourier transform infrared (FTIR) spectroscopy. The incorporation of TA after Fe3O4 NPs production generated spherical NPs smaller than 10 nm, suggesting that TA plays a fundamental role in the nucleation and organization of Fe3O4 NPs. Data from both density functional theory (DFT) and FTIR allowed us to infer that Fe3O4 interacts mainly with the carbonyl groups of TA. Hybrid materials having improved water-dispersibility are very attractive for biomedical applications., The authors acknowledge the financial support from CNPq (470996/2011-0 and 304684/2011-2 projects), CAPES (nBioNet), FAPEPI, MICINN (Spain) for project MAT 2011-25870, and CENAPAD-UFC by availability of computational resources used in the development of theoretical calculations.

The complex trans-[Ru(NO)(NH3)4{P(OEt)3}](PF6)3 undergoes nucleophilic attack on the phosphorus ester ligand in the solid state yielding trans-[Ru(NO)(NH3)4{P(OH)(OEt)2}](PF6)3. The reaction was monitored and the products analyzed using nuclear magnetic resonance spectroscopy (31P{¹H} CP-MAS NMR and 31P{¹H} NMR), infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR), cyclic voltammetry (CV), electronic spectroscopy (UV-Vis) and elemental analysis. According to experimental data and quantum mechanical calculations (DFT), the reaction proceeds in the solid state by the nucleophilic attack on the phosphorus ligand, promoted by the strong polarization along the P III-RuII-NO+ axis induced by the nitrosyl ligand, and takes place following the Michaelis-Arbusov type mechanism for phosphorus ester hydrolysis. In solution, the nucleophilic attack occurs simultaneously at the nitrosyl and triethylphosphite ligands, yielding trans-[Ru(H2O)(NH3)4{P(OEt)3}]2+ and trans-[Ru(NO)(H2O)(NH3)4]3+ in comparable amounts. Neste trabalho foi investigado o ataque nucleofílico sofrido no estado sólido pelo complexo trans-[Ru(NO)(NH3)4{P(OEt)3}](PF6)3, no éster de fósforo coordenado, originando como produto a espécie trans-[Ru(NO)(NH3)4{P(OH)(OEt)2}](PF6)3. A reação foi monitorada e os produtos caracterizados utilizando ressonância magnética nuclear (31P{¹H} CP-MAS NMR e 31P{¹H} NMR), espectroscopia no infravermelho (FTIR), ressonância paramagnética eletrônica (EPR), voltametria cíclica (CV), espectroscopia eletrônica (UV-Vis) e análise elementar. De acordo com os dados experimentais e cálculos de mecânica quântica (DFT), a reação ocorre no estado sólido pelo ataque nucleofílico no éster de fósforo coordenado devido à forte polarização no eixo P III-RuII-NO+ induzida pela presença do ligante nitrosilo. A reação segue o mecanismo tipo Michaelis-Arbusov para hidrólise de ésteres de fósforo. Em solução (pH 7,0), o ataque nucleofílico ocorre nos ligantes NO+ e P(OEt)3, gerando como produtos os complexos trans-[Ru(H2O)(NH3)4{P(OEt)3}]2+ e trans-[Ru(NO)(H2O)(NH3)4]3+ em proporções comparáveis.

Quantum chemical calculations were performed in order to obtain molecular properties such as electronic density, dipole moment, atomic charges, and bond lengths, which were compared to qualitative results based on the theories of the organic chemistry. The quantum chemistry computational can be a useful tool to support the main theories of the organic chemistry.

This work presents a density functional theory study of the norbornene ROMP metathesis reactions. The energies have been calculated in a Grubbs catalyst model Cl2(PH3)2Ru=CH2. The geometries and energy profile are similar to the Grubbs metilydene (Cl2(PCy3)2Ru=CH2 real model. It was found that the metathesis reaction proceeds via associative mechanism (catalyst-norbonene) followed by dissociative substitution of a phosphine ligand with norbonene, giving a monophosphine complex. The results are in reasonable agreement with the available experimental data. The dissociation energy of the phosphines is predicted to be 23.2 kcal mol-1.