Ref.: EmaMss33-001
Apresentador: Vitória Maria Rodrigues Vasconcelos
Autores (Instituição): Vasconcelos, V.R.(Universidade Federal do Ceará); Bezerra, E.M.(Universidade Federal Rural do Semi-Árido); Postacchini, B.B.(Universidade Federal de Ouro Preto); Costa, R.F.(Universidade Federal Rural do Semi-Árido); Freire, V.N.(Universidade Federal do Ceará); dos Santos, H.S.(Universidade Estadual Vale do Acaraú); de Vasconcelos, I.F.(Universidade Federal do Ceará);
Resumo:
Photophysical properties of small organic molecules have been the subject of intensive investigation due to their potential optoelectronics, electrochemical, and biological applications. However, solvents have the potential to induce modifications in electronic spectra and, therefore, computational tools that can accurately forecast the absorption and emission properties of solvated compounds become highly significant. In this study, we coupled a quantum mechanics (QM) method with an implicit solvation model to explore the optical absorption spectra of dicinnamalacetone chalcone-based chromophore ((1E,3E,6E,8E)-1,9-diphenylnono-1,3,6,8-tetraen-5-one) in various solvents with increasing polarities. For this purpose, molecules were initially subjected to conformational calculation in Materials Studio, using the Universal Force Field (UFF) parameter set and the systematic grid scan method from the Conformers module. Subsequently, quantum chemical calculations were performed using the Gaussian 09 software package. In this process, the most stable conformer classically calculated was employed to calculate the geometry and the harmonic vibrational frequencies of the ground state (S0) through Density Functional Theory (DFT) using the M06-2X meta-hybrid exchange-correlation functional with the 6-311+G(d,p) basis set. Finally, the ground state optimized structures were employed for Time-Dependent Density Functional Theory (TD-DFT) calculations to determine the 50 lowest-energy singlet-singlet vertical electronic transitions using the M06-2X/6-311+G (d,p) method. All calculations were performed using the Polarizable Continuum Model (PCM) of the self-consistent reaction field (SCRF) theory for the toluene (?=2.37), dichloromethane (?=8.93), o-dichlorobenzene (?=9.99), acetone (?=20.49), acetonitrile (?=35.67), dimethylsulfoxide (?=46.826), and water (?=78.35). As the solvent polarity increased, the dicinnamalaceton molecule exhibited a bathochromic shift in its absorption spectra, attributed to ?-?* transitions and intramolecular charge transfer interactions. This observation indicated that the molecule was more solvated in the singlet excited state than in the ground state, leading to a decrease in excitation energy. However, a smaller bathochromic shift was observed in water, implying that in solvents where the molecule is insoluble or partially soluble, the surrounding microenvironment, such as solvatal reorganization and specific solute-solvent interactions, affects the observed electronic transitions.