Theoretical study of Rifampicin using the Density Functional Theory – DFT
INTRODUCTION: Leprosy is a disease caused by the bacillus mycobacterium leprae (M. Leprae), which causes damage to the skin, and mainly the peripheral nerves. According to the World Health Organization (WHO) leprosy is considered a public health problem, as it affects several people around the world. Among the compounds used in the treatment of leprosy, there is Rifampicin (RIF), being considered an essential substance for this purpose. OBJECTIVE: Thus, this work aimed to simulate the chemical properties of RIF using the density functional theory (DFT). MATERIALS AND METHODS: The chemical structure of RIF was designed using the Chemcraft software, generating the corresponding Cartesian coordinate matrices for the generation of the input files for computational calculations, which were performed with the Gaussian software 16. Vibrational frequencies were also obtained, considering all positive. These files were analyzed by the functional ωB97x-D, the base function set 6-31G (d, p) and the PCM (Polarizable Continuum Model) solvation model using ethanol as a solvent. Subsequently, from the optimization of geometry and the results of vibrational frequencies, the values of Dipolar Moment (MD), HOMO-LUMO energy, Gap, electronegativity (χ), chemical potential (µ), hardness (ꞃ), softness (s) and global electrophilicity (ω) were calculated. For the site of the regions with the highest electronic density, it was possible to obtain the electrostatic potential map (MPE). RESULTS: The RIF has different nucleophilic (higher electron density) and electrophilic (lower electron density) regions. With the results of vibrational frequencies, such as absorption bands in the infrared (IR) region, the spectra agree with the experimental results. CONCLUSION: Thus, these results are quite promising since from the calculated energies and vibrational frequencies it is possible to clarify interactions of the different compounds using the DFT method, as occurs in characterization and synthesis studies to obtain solid dispersions.
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