Estudo e caracterização estrutural e termodinâmica de compostos de inclusão formados entre antidepressivos e ciclodextrinas

Abstract

In this work the supramolecular systems stabilized by the non-covalentinteractions, formed by association of the ß-cyclodextrin with a bicyclic and a tricyclic antidepressant, Fluoxetine and Imipramine respectively, were investigated by spectroscopies techniques (FT-IR, FTIR-HATR and NMR), thermal analysis (TGA and DSC) and also by calorimetric technique (ITC). The utilization of these physical-chemistry methods of analysis allowed to propose not only the supramolecular structure of the inclusion complexes, but also to define their thermodynamic parameters.The results obtained by the spectroscopies techniques (FT-IR, FTIRHATRand NMR), to the ßCD/FLU supramolecular complex, indicated threepossibilities of complex in solution simultaneously. The first possibility, and also the most stable the inclusion compound, is that when the Fluoxetine aromaticring, in which the CF3 group is presented, interacts with the ßCD cavity. The other inclusion compound occurs when the Fluoxetine monosubstituted aromatic ring is included into the ßCD cavity. In addition, the Jobs plot suggests, also the existence of a supramolecular complex in 2:1 ßCD/FLU molar ratio, possibly when probably; both aromatic rings of FLU are included in the ßCD cavity. However, the ITC results indicated the 1:1 ßCD/FLU as the most stable complex in solution, also providing the thermodynamic parameters(.Gº = -21.5 kJ.mol-1, .Hº = -17.2 kJ.mol-1 e T.Sº = 4.3 kJ.mol-1). Thedifference between these two stoichiometries found might be explained by the different physical-chemistry probes used to investigate the interactions between ßCD and FLU. To the ßCD/Imipramine inclusion compound, the spectroscopies methods (FT-IR, FTIR-HATR and NMR) indicated the interaction between the both Imipramine aromatic rings with all ßCD hydrogens. In addition, when ßCD concentration increases in solution the interactions between the host and guest molecules became more evident. The Jobs plot demonstrated the existence of two possibilities of supramolecular complex; first when the ßCD oncentration is lower than Imipramine (1:2 ßCD/IMI), and other when the ßCD concentration is higher in solution (2:1 ßCD/IMI). However, the 2:1 ßCD/IMI complex is the most stable. The ITC experiments make possible to determinate the thermodynamic parameters (.Gº = -21.9 kJ.mol-1, .Hº = -30.6 kJ.mol-1 e T.Sº = -8.7 kJ.mol-1) to the inclusion reaction, the equilibrium constant and also the complex stoichiometry, which this last is in accordance with the results obtained by Jobs experiments.