Síntese, caracterização e potencial atividade leismanicida do complexo [RuCl(BNT)(p-cym)]

Abstract

Ru(II)-based complexes have been investigated due to their chemical versatility and strong potential in pharmacological applications. In this work, the synthesis and spectroscopic characterization of the complex [RuCl(BNT)(ƞ⁶-p-cym)] were carried out, aiming at applications in in vitro studies for leishmanicidal activity. The complex [RuCl(BNT)(ƞ⁶-p-cym)] was synthesized from the precursor dimer [RuCl₂(ƞ⁶-p- cymene)]₂ and the ligand 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedionate (BNT). The geometry of the synthesized complex was suggested through spectroscopic techniques, such as infrared spectroscopy (ATR-FTIR), proton nuclear magnetic resonance (¹H NMR), mass spectrometry, ultraviolet-visible absorption spectroscopy (UV-Vis), and it was also subjected to antiparasitic activity assays. The ¹H NMR spectrum shows chemical shifts consistent with the expected values for the protons of the coordinated ligands. These signals appear deshielded compared to those of the free ligands due to the interaction with Ru(II), with special emphasis on the singlet of the β-diketonate at 6.4 ppm, which confirms its coordination to ruthenium(II). In addition, elemental analysis was performed to quantify the percentage of C and H, showing strong agreement between the experimental and theoretical values for the proposed structure. Mass spectrometry revealed an m/z value corresponding to the complex structure without the chloride ligand, as expected for this type of analysis. IR spectra were obtained for both the dimer and the complex, showing that, for the complex, the spectrum lacks the bridging Ru–Cl vibrational mode, evidencing its cleavage in the formation of the final complex. UV-Vis spectra also provided evidence of β-diketonate coordination. The compound exhibited activity against the promastigote form of L.(L.) amazonensis at the highest concentrations tested, while the precursor was inactive, indicating that the coordination of β-diketonates to [RuCl₂(ƞ⁶-p-cymene)]₂ represents an interesting strategy to generate compounds with leishmanicidal activity.