Licenciatura em Química (Sede)
URI permanente desta comunidadehttps://arandu.ufrpe.br/handle/123456789/26
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Resultados da Pesquisa
Item Estudo da absorção eletrônica do complexo de európio u(bzac)3.2H2O pelo método TDDFT com uso da aproximação da carga pontual para o íon Eu(III)(2022-06-08) Silva Neto, Nelson Cardoso da; Batista, Hélcio José; http://lattes.cnpq.br/1234630357325796; http://lattes.cnpq.br/5491959849189946In this work, using quantum chemistry methods based on density functional theory (DFT), spectroscopic properties such as electronic absorption in the ultraviolet region of coordination compounds with Ln(III) lanthanide ions were studied; in particular, tris-betadiketonates compounds with Eu(III) ion with two water molecules completing the coordination sphere with the general formula Eu(bzac)3.2H2O (bzac=bezoylacetone), resulting in a coordination number equal to eight . Molecular structures were optimized using the MOPAC 2016 program with the Sparkle/AM1 method. The approximation used in the Sparkle model simulates the lanthanide ion by a point charge, considered adequate due to the essentially ionic behavior of the ion-ligand bond, resulting from the shielding of the 4f valence orbitals by the filled 5s and 5p shells. The optimized structures were submitted to the TDDFT (Time Dependent DFT) method implemented in Orca 4.2.1, with the B3LYP/6-31G(d) protocol, to obtain the excited states, located in the ligands, of singlet and triplet spin multiplicities. In these calculations, the Eu(III) ion was replaced by a point charge which, based on Batista and Longo's (2002) model, was varied between +3.0 and 3.5e. Using the excited states wave functions and the transition oscillator strengths, the absorption spectra were simulated by means of a Lorentzian shape, for comparison with available experimental data. To obtain the spectral curves, the Avogadro program was used. The TDDFT calculation was carried out at two levels: complete TDDFT and TDDFT-TDA (Tamm-Dancoff approximation), with 100 roots, a suitable value for the studied spectral region and with a moderate computational cost. The bands of interest in the luminescence of the complexes are those of lower energy (low lying states), and for those the full TDDFT method provided better results than the TDA method, when compared to the experimental data. Regarding the use of the point charge approximation, the value of +3.0e provided the best prediction than larger values, contrary to what was proposed by Batista and Longo with the use of semi-empirical methods instead of DFT, indicating that this the latter method does not show the same behavior as the INDO/S approximation upon increasing the point charge value, suggesting additional studies on the nature of the excited states described by DFT methods for such compounds. All the conclusions about the results obtained by the full and TDA-TDDFT methods and the trend of band displacements according to the variation of the point charge, referring to the model compound Eu(bzac)3.2H2O are in line with calculations carried out for compounds similar to this one, with betadiketone ligand btfa (benzoylacetone) in place of bzac and with the ligand bipy (bipyridine) replacing the two water molecules in the coordination sphere.Item Teoria do Orbital Molecular e Ressonância Não-sincronizada para supercondutores metálicos(2022-06-02) Anjos, Eduardo Victor Santana dos; Bastos, Cristiano Costa; http://lattes.cnpq.br/6385190604693576; http://lattes.cnpq.br/4546705612868813It was used the Molecular Orbital Theory (MOT) and the RVB Theory (Resonating Valence Bonding) to study metallic superconductivity. From the occupations of the natural orbitals, obtained using the Hartree-Fock-Roothaan method and the LanL1MB basis function, we used the average valences and the variations of metallic radius to calculate the critical temperature (Tc) of thirty-seven metals. A consistent prediction for the critical temperatures of superconducting metals was made and cor-rectly determined eight metals that are not superconducting under normal conditions Au, Ag, Cu, Sc, Y, Mn, Fe, Ni and Co, obtaining Tc tending to zero. Linear regression between critical temperature predictions and experimental values gave a satisfactory value with a coefficient of determination of 0.95. It was possible to classify ten crest superconductors and eighteen trough superconductors, applying the Pauling meth-odology that correlates the phonon wave with electron transfer. No such prediction had been made so far.Item Estudo Teórico de Propriedades Estruturais e Eletrônicas e a construção de Modelos QSAR aplicados ao Cálculo da LD50 de alguns Neurotransmissores(2019-07-10) Santos, Douglas Amorim dos; Bastos, Cristiano Costa; http://lattes.cnpq.br/6385190604693576; http://lattes.cnpq.br/0592521567528784Neurotransmitters are chemicals produced by neurons with the biosignaling function, acting on synapses, which are the junction point of the neuron with another cell. There are three main categories of neurotransmitters, amino acids, biogenic amines and peptides. Studies have been conducted to understand how these substances are synthesized, their storage, transport and synapse mechanisms. In this work, molecular modeling was performed for nine neurotransmitters, Dopamine, Serotonin, Acetylcholine, Glutamic Acid, Adrenaline, Morphine,-Butyric Acid, Melatonin and Noradrenaline. Molecular modeling was performed using ab initio (HF and MP2), Density Functional Theory (DFT-B3LYP) and Semi-Empirical (AM1) methods, using the Gaussian 09 program. structural and electronic structures for the nine molecules, including total energy, Homo orbital energy and Lumo, ionization potential, electronic a nity, neutral molecule volumes, and the volume of their cations and anions, etc. These properties were analyzed by quantitative structure-activity relationship (QSAR), and mathematical models were constructed to predict, through multivariate analysis, the LD50 for these moleculesItem Síntese eletroquímica da estrutura metal-orgânica de [Cu3(BTC)2 .(H2O)3]n e sua aplicação em biossensores e meio ambiente(2018-08-27) Silva, Renata Pereira da; Freitas, Kátia Cristina Silva de; http://lattes.cnpq.br/9622769576689246; http://lattes.cnpq.br/9318114882701456The MOFs (Metal-Organic Frameworks) are a new class of materials known as porous coordination networks, form an extensive class of crystalline materials, featuring a central atom (metal ion) or sintered (metallic cluster) coordinated the organic molecules (ligands), in which this unit metal-ligand repeats itself forming a polymer metal complex network in one, two or three dimensions. One of the most important properties of this metal-organic framework is the high porosity and large surface area, properties that are exploited for the development of a textile dye adsorbent material in effluent and as crippling to the Lectin of Cratylia Mollis, a specific enzyme for glucose. The MOF [Cu3 (BTC) 2 ( H2O) 3] n was obtained by electrochemical synthesis and by current limiter using an acid solution 1, 3, 5-benzenotricarboxilico, sodium nitrate and dimethylformamide in water Mllipore a ratio of 1:1. The precipitate was filtered, washed and dried in an oven at 120° C, and then was characterized by absorption spectroscopy in the infrared region using a Fourier transform with spectrophotometer (FTIR) and by cyclic voltammetry. After this MOF mix with a solution that simulated a textile effluent, it was found that it can be used in your treatment as it was retrieved from a colorless effluent and the stabilization of the dye in your structure. The developed biosensors have been drawn up with the MOF with the lectin, and graphite paste in Platinum and gold electrodes. The cyclic voltammetry of these systems in solution of glucose and fructose. Indicating that the lectin interacts with low-concentration glucose solutions with the gold record (10:15, 5 mM due to the increase of the cathode and Anodic peaks), while that with the Platinum card she interacts with high concentrations of glucose (20, 40 and 60 mM due to the increase of cathode and Anodic peaks). Interaction not observed of the lectin with fructose, as expected. This system can be used for the identification of glucans in effluents, and identification of glucose in real samples, not requiring a large amount of sample for identification, making the low-cost and efficient method.