Estudo teórico de propriedades espectroscópicas de bases nitrogenadas e derivados de vitamina A em solução
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2012-03-23
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Universidade Federal de Goiás
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In this work we present a theoretical study for the optical absorption spectrum UV-VIS and nuclear magnetic resonance (NMR) parameters of molecules that forming the structure of the deoxyribonucleic acid (DNA): adenine, guanine, thymine and cytosine in aqueous solution and of aldehydes and carboxylic acids derivatives of vitamin A in solution of chloroform, acetonitrile, methanol and water. The Solvent effects are treated using a sequential methodology that combines Monte Carlo simulation and quantum mechanics calculations (S-MC / MQ). Effects of polarization of the reference molecules by the solvent are obtained iteratively assuring the convergence of the dipole moment in solution, with the atoms of the solvent molecules modeled by point charges. The results show that the polarization effect can give marked increases for the dipole moments of the reference molecules, especially in water, as compared with the results of gas phase. TD-DFT calculations for the vertical electronic transitions were performed with hybrid functionalities: B3LYP, PBE1PBE and BHandHLYP; and with long-range corrected functionals: CAM-B3LYP and LC-wPBE. For the isotropic magnetic shielding constants, GIAO-B3LYP results were obtained with several basis set functions: 6-311 ++ G (2d, 2p), AUG-cc-pVTZ, pcS-2, pcS-3 and AUG-pcS -2. The results obtained show the optical absorption spectrum variations between 6 and 28 nm for the nucleotide bases and between 13 and 80 nm for the derivatives of vitamin A with the functional type, whereas that for the NMR parameters of carbon atoms variations between 3 and 10 ppm with the choice of the basis set functions. However, the inclusion of the solvent polarization effects provides a reliable description for these electronic properties in solution, in comparison with available experimental results. The classical simulations were performed with the DICE program and the quantum calculations with the GAUSSIAN03 / 09 program.
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OLIVEIRA, Guilherme Colherinhas de. Estudo teórico de propriedades espectroscópicas de bases nitrogenadas e derivados de vitamina A em solução. 2012. 363 f. Tese (Doutorado em Física) - Universidade Federal de Goiás, Goiânia, 2012.