Propriedades eletrônicas e espectroscópicas de um isômero da tiroxina

Abstract

The analysis, both theoretical and experimental, of the vibrational spectra of a molecule can be considered its "fingerprint", as the resulting characterization is intrinsic and unique in the sense of differentiation between molecules and its usefulness in any area of study of materials and organic compounds. Therefore, in this work, we systematically study the structural, vibrational and electronic properties of the ground state of the isolated thyroxine molecule (IUPAC L-3,5,3’, 5’-tetraiodothyronine). Due to the great complexity of molecular systems, caused both by the large number of particles present in the system and by the interaction effects of these particles, we use algorithms built with quantum chemistry methods that aim to reduce the computational cost while producing sufficiently accurate results for research in physics. We used the Hartree-Fock method for the treatment of electronic wave functions and the Density Functional Theory in order to obtain the electronic correlation of the system, the functional B3LYP was selected as it is a functional widely used in molecular simulation due to the excellent description that its hybrid character is capable of producing; the other functional that was used is the BP86 functional, not yet tested to describe the thyroxine molecule. In this way, it is possible to compare a functional less used with another one already known in scientific productions. The results for both were compared to experimental results from cited references. Finally, the results obtained through the functionals were studied in cases of vibrational excitation produced by simulation of infrared and Raman spectroscopy; and in cases of electronic excitation, in which UV-Vis spectroscopy was used. It is noteworthy that there are few studies prior to this one in the literature for the thyroxine molecule, especially when it comes to its transitional character.