ESTUDOS ESPECTROSCÓPICOS E ELETROQUÍMICOS DA PORFIRINA MESO TETRAKIS (N- METIL -4- PIRIDIL) ( TMPYP ) EM MEIO MICELAR

Abstract

In this work we used cationic porphyrin meso-tetrakis TMPyP in the form of free base and as a simplified model of membrane detergents CTAB, Brij 78 and SDS. The study of the interaction of porphyrin with the micelles was performed using the techniques of optical absorption and electrochemistry. The experimental results obtained of spectroscopy measurements show that both in acidic and in alkaline medium , a shift of the spectrum of porphyrin to longer wavelengths and a isosbestic point at 433 nm and 437 nm for the acid and basic medium respectively, caused by protonation and deprotonation of the porphyrin. There was an effective interaction between the porphyrin and the SDS micelles. In the presence of CTAB micelles and BRIJ 78 no significant changes and the concentrations of HCl and NaOH suggesting no interaction of porphyrin with the surfactant CTAB, and a small interaction with surfactant BRIJ. The voltammetric results showed that the effect of substituents can affect the peaks of oxidation and reduction and as a result alter the energy required to oxidize or reduce the TMPyP. A similar behaviour of porphyrin in buffer was observed. In the presence of SDS micelles, the porphyrins have energies of GAP- like porphyrin in buffer. Already in the presence of micelles of CTAB and BRJ 78 the energies of GAP were lower. Thus, the results indicate that there is an effective interaction with the SDS micelle, a small interaction with the micelle BRIJ and no interaction with the micelle of CTAB. The UV-VIS and electrochemical techniques indicate the presence of at least three species in equilibrium porphyrin studied : the free base species, protonated and the deprotonated.