Estudo computacional das propriedades eletrônicas de corantes indólicos substituídos por grupos NO2 e NHAc

Abstract

In this work the absorption spectrum in gas phase and with solvent (acetonitrile) is studied together with the structural and electronic properties of the dyes Indole-NO2 and Indole-NHAc using the time-dependent density functional theory (TD-DFT). The level of calculation used is the Density Functional Theory (DFT) for optimizations and its time-dependent component, TD-DFT, together with the B3LYP and PBE0 exchange-correlation functionals for structure optimizations, and CAM B3LYP, PBE0, M06-2X and wB97XD for electronic properties, all with the basis set 6- 311 ++ G (d, p). The optimization of the structure was obtained by observing the vibrational modes, which did not obtain any imaginary frequency. Using the scale factors, both functional B3LYP and PBE0 showed a good correlation with the experimental infrared spectrum data, with B3LYP standing out for Indol-NO2 and PBE0 for Indol-NHAc considering the band with the greatest contribution of the N-H stretch. For the electronic properties, all four functionals present good results, mainly using the explicit IEFPCM method for the acetonitrile solvent, which leads to a bathochromic shift of the absorption spectra. PBE0 presents good results, with lower energies for the first excited state of both dyes and smallest relative error (2.5%) for the absorption spectrum of Indol-NHAC, and with a lower computational cost, while wB97XD presents the smallest relative error (0.8%) for Indol-NO2. Indol-NO2 has a smaller band gap than Indol-NHAc due to the greater electronegativity of its substituting group, making it a more interesting dye in several applications such as in the confection of Dye-sensitized solar cells.