Síntese e caracterização do complexo cis-Ru(bpy)₂(pyr)₂₂

Abstract

Metal complexes have been reported in the literature as potential therapeutic drugs, encompassing applications in the treatment of inflammation, rheumatoid arthritis, cardiovascular diseases, cancer, and diabetes mellitus. Studies suggest that the coordination of bioactive molecules to metal centers can enhance the therapeutic effects of these substances. However, inorganic compounds represent only 1% of the drugs approved for clinical use, highlighting an area with untapped potential. In this context, the present paper reports the synthesis and characterization of the cis-[Ru(bpy)₂(pyr)₂](PF₆)₂ complex, where bpy = 2,2′-bipyridine and pyr = pyrazinamide. Both ligands are molecules with well-established pharmacological activities, with pyrazinamide being a first-line antibiotic used in the treatment of tuberculosis. The compound was synthesized from the precursor complex cis-[Ru(bpy)₂Cl₂] and characterized through electronic spectroscopy in the ultraviolet-visible region, vibrational spectroscopy in the infrared region, and cyclic voltammetry. Characteristic π→π* bands of the pyrazine ligand at 207 and 254 nm, as well as a metal-to-ligand charge transfer (MLCT) band at 458 nm, were observed in the electronic spectrum obtained in an aqueous medium for the synthesized compound. Additionally, its vibrational spectrum obtained via ATR displayed expected characteristic peaks for its structure, such as the carbonyl stretching at 1662 cm⁻¹ and the asymmetric and symmetric N-H stretches at 3644 and 3376 cm⁻¹, respectively. Meanwhile, the cyclic voltammogram revealed a half-wave potential (𝐸₁/₂) of 573 mV, indicating a shift of 55 mV toward higher redox potential compared to the precursor voltammogram (518 mV). This behavior is consistent with the coordination of pyrazinamide, attributed to its π-acceptor character. Furthermore, a reversibility study conducted via cyclic voltammetry at varying scan rates demonstrated that the redox process is diffusion-controlled. The results provided by the three employed techniques indicate the formation of the compound of interest.