Estudo téorico do efeito do solvente no fenômeno de emissão por agregação em derivado de pireno com potencial para detecção de água em etanol

Abstract

This work presents a theoretical-computational study of a pyrene-based fluorescent probe, named PyQ, aiming to evaluate its potential as an optical sensor for detecting adulterants in fuel ethanol. The study focuses on investigating the aggregation-induced emission (AIE) phenomenon, exploring the effects of the solvent environment (water and ethanol) and aggregation states on the photophysical properties of the probe. To achieve this, Density Functional Theory (DFT and TD-DFT) calculations and Molecular Dynamics (MD) simulations were performed using both implicit solvation models (CPCM) and explicit solvent models (cluster approach). The results demonstrate that explicit solvent modeling is essential for accurately representing solvent effects, as the continuous model was insufficient to differentiate between solvents. Pyrene dimerization was found to be thermodynamically favorable in water when explicit solvation interactions were considered, while intramolecular aggregation of the PyQ probe predominantly occurred through J-type stacking, reinforced by hydrogen bonding in aqueous media. The calculated photophysical properties revealed that PyQ has a non-zero dipole moment and that aggregation enhances its emission, supporting the AIE mechanism observed experimentally. Specifically, in water, 99% of the aggregates exhibited J-type stacking, which favors emission. Despite the limitations of the cluster model, due to the reduced number of solvent molecules and the simplified representation of aggregates, the study provides consistent theoretical support for understanding the emissive behavior of the PyQ probe. It is concluded that the combination of computational chemistry techniques is a promising approach for developing efficient optical sensors for adulterants in biofuels.