Investigação eletroquímica de naftoquinoas funcionalizadas com selenociana

Abstract

Electrochemistry has been frequently used to understand, simulate or explore natural systems using techniques such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Among natural products, quinones have attracted the interest of researchers due to their dualaction capacity as anti- and pro-oxidants. The multi-target mechanisms of quinones stimulate the search for new molecular variations, such as the combination of two or more classes of compounds with biological activity, in order to improve their pharmacological potential and/or reduce their adverse effects. In this work, the electrochemical and spectroelectrochemical study aims to investigate the redox behavior of a series of synthetic and novel naphthoquinones substituted with selenocyanate, using the aforementioned electrochemical techniques. The electrochemical studies were performed in a conventional cell with three electrodes: glassy carbon (working electrode), platinum (counter electrode) and Ag/AgCl/Cl− (reference electrode). For samples 1 and 3, the experiments were also performed using the platinum electrode as the working electrode in order to avoid divergences in the spectroelectrochemical studies. The CVs of eight selenocyanate-hydridized naphthoquinones (SeCN) were recorded in an aprotic medium (ACN + TBAPF6 0,1mol L-1 ) to resemble the lipophilic environment typical of cell membranes. The analyses were performed in the cathodic scanning range between 0 and -2,7 V and in the anodic scanning range between 0 and 2,2 V. The spectroelectrochemical studies were performed in a thin-layer quartz cuvette, using three electrodes: platinum (Pt) grid (working), Pt wire (counter electrode) and the Ag/AgCl/Cl− system (reference). The spectra were recorded in the cathodic scanning range between 0 to -1,5 V and in the anodic scanning range between 0 and 1,5 V and during the application for 180 s of the potentials of the cathodic peaks obtained by CV, both with the glassy carbon electrode and with the platinum electrode, at a speed of 100mV s-1 . For all compounds, cyclic voltammograms of complex profiles with at least four cathodic peaks were obtained, the first two being related to the usual behavior of quinones widely reported in the literature. It was possible to elucidate that the other waves are related to the formation of quinonamethides and dimers via reductive elimination, since the spectral data confirmed possible relevant structural changes in the compounds MENSeCN and MENPhSeCN. From this, we propose the reduction mechanism that can be explained via dissociative electron transfer (TED), with the leaving group being the SeCNspecies. In this way, it was possible to electrochemically obtain relevant information that could predict or corroborate future analyses of the biological activities of this new series of unprecedented compounds.