Efeitos térmicos e da polaridade de solventes sobre as propriedades espectroscópicas de compostos orgânicos com transferência de carga intramolecular

Abstract

The investigation of spectroscopy properties of organic compounds has been widely realized with the purpose of identifying and characterizing new materials with potential application in electro-optical devices. In this point of view, this work hás as the main subject the study emission and absorption phenomena of two fluorophores that containin the dansyl group in their chemical structures. Such materials are particularly interesting due to the existence of a dual fluorescence associated with the phenomenon of intramolecular charge transfer mediated by the twist of their molecular structure. In particular, the thermal and solvation effects on the fluorescence properties of the compounds are studied. It was observed that the processes of absorption and steady-state emission exhibit a strong dependence on the solvent. By using distinct model to describe the Stokes shift induced by thei solvent polarity, we estimate the dipole moments of the fundamental and excited states of molecules. Concerning with thermal effects, its was observed a pronounced enhancement in the flourescence intensity of the compounds as the temperature of the system was increased. The analysis of the thermal effects was perfomed in the context of thermal activated transition rates, where a new mechanism is proposed.