Estrutura eletrônica de fármacos de interesse comercial

Abstract

The computational simulation of drug molecules grows in the same measure of advances in hardware and software technologies. The methods of Quantum Mechanics theory, which are based in solving n-body Schrödinger Equation, permits the calculation of many properties of these molecules, like geometry, charge distribution and dipole moment, electronic levels and molecular orbitals, electronic transitions (UV-Vis spectrum) and vibrational transitions (Infrared and Raman spectra). These methods are usually separated in three categories: (i) ab initio, for those which calculation is entirely theoretical, based on Hartree-Fock theory, (ii) semi-empirical, for those which employ experimental parameters for simplification of ab initio methods, and (iii) Density Functional Theory (DFT) methods, which, as name suggests, are based on functionals of electronic density functions. The objective of this paper was to obtain the electronic properties of three drugs of commercial interest, namely: adapalene (ADAP), manidipine (MAN) and tacrolimus (TAC), by using five SE methods and one DFT. Results were compared in three schemes: SE/SE, SE/DFT and DFT/DFT, where in the first is indicates the method used in geometry optimization, and in the second the method used to extract electronic and vibrational properties. In general, it was verified consistency in results of geometry description and electronic properties, with a few differences in HOMO – LUMO gap (Δ) and dipole values. For spectra, it was observed that SE/DFT and DFT/DFT schemes presented, in general, a better description of the drugs, with significantly less deviation and dispersion from experimental values. In Raman spectra,dispersion appeared lesser in comparison with Infrared spectra, for in these, few stretching modes where obtained in literature, whose values deviate considerably from experimental.