Areno complexos de rutênio contendo ligantes derivados de hidrazidas: síntese, caracterização e estudo da estabilidade

Abstract

A large number of coordination compounds have been studied in the last decades with the aim of developing more effective drugs for the treatment of various diseases. Among these, ruthenium (II) compounds are of great interest due to their ability to participate in redox reactions capable of promoting the generation of reactive oxygen species (ROS) in biological media, which are harmful to pathogenic biological agents. However, the stability of the complexes is a fundamental point for their use as a possible drug. In this sense, the present work aimed to develop new organometallic ruthenium complexes with potential medicinal use based on ruthenium arene-complexes containing hydrazide-derived ligands and to study their stability. Initially, a series of three complexes were synthesized, using as precursor the complex [{RuCl2(η6-p-cym)}2] and the thiosemicarbazide ligands HLR (R = allyl, phenyl and fluorophenyl), forming complexes of composition [RuCl(η6-p-cym)(HLR)]PF6. The obtained complexes were characterized by electronic spectroscopy, infrared spectroscopy, elemental analysis, mass spectrometry, 1H NMR and had their molecular structure optimized by computational calculations (DFT). However, the UV-Vis and 1H NMR measurements indicated the instability of the complexes in solution, concluding that there was a need to prepare new precursors to obtain more stable complexes. Thus, the precursors [RuCl(η6-p-cym)(bipy)]PF6 and [RuCl(η6-p-cym)(o-phen)]PF6 were used to prepare two new series of complexes with composition [Ru(η6-p-cym)(bipy)(HLR)]PF6 and [Ru(η6-p-cym)(o-phen)(HLR)]PF6. The characterizations performed were used for the two new series of complexes, however, it was found that even containing the N-heterocyclic ligand, the thiosemicarbazide derivatives did not present stability in solution. Finally, a new complex was prepared using 2-(di(pyridin-2-yl)methylene)-N-phenylhydrazinecarboxamide (HDPKPhS) as ligand, a compound from the semicarbazone class. In fact, the characterizations indicated that the ligand acts in N,N-bidentate coordination mode, which led to the stability of the complex in solution. Thus, it is possible to conclude that ruthenium arene complexes with similar ligands to HDPKPhS are promising compounds to be evaluated in biological studies.