Novos complexos fenantrolínicos de cobre e cobalto com ligantes derivados do monastrol: síntese, estudo espectroscópico e eletroquímico

Abstract

Cobalt and copper complexes stand out as promising systems in the treatment of cancer, both due to the low toxicity of these metals in the biological environment, as well as the magnetic and electrochemical properties, making it quite interesting from the biological and medicinal point of view. In addition to metals, there is also a search for systems with bioactive ligands, for example monastrol derivatives, which can together with metal form structures with properties highly relevant for a pharmacoligal point of view. Thus, this work is presented, with the aim of contributing to the inorganic chemistry of Co(II) and Cu (II) systems, with the synthesis and spectroscopic and electrochemical characterization of new complexes with monastrol derivatives in systems [M(phen)(S-Cros)2] and [M(phen)(O-Cros)2], where M = Co(II) e Cu(II), phen corresponds to 1,10- fenantrolina, S-Cros = ethyl 4-(4-hydroxy-3-methoxyphenyl)-6-methyl-2-thioxo-1,2,3,4- tetrahydropyrimidine-5-carboxylate, and O-Cros = ethyl 4-(4-hydroxy-3-methoxyphenyl)-6-methyl2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate. All complexes were synthesized by adding to the precursor complexes [Co(phen)Cl2] and [Cu(phen)Cl2] the ligands S-Cros and O-Cros, in the ratio of 1:2 from precursor to ligand, using water as solvent, adjusting the pH to 11. The ligands were initially characterized by NMR 1H spectroscopy in DMSO-d6, presenting good correlation between the chemical shifts and the hydrogens in the molecules of S-Cros and O-Cros. Analyzing the vibrational spectra obtained in KBr pellets on the [M(phen)(S-Cros)2] and [M(phen)(O-Cros)2] systems, phenantroline bands in the complexes displays near the region of 1427, 854 and 723 cm-1 attributed to the stretching modes C-N and δ C-H, in addition to the S-Cros ligand bands, with stretching modes at 1692 (C=O), 1202 (C=S), 1029 (C-O ether) and 751 cm-1 ( C=S) and vibrational modes of the OCros at 1696 (C=O ester), 1642 (C=O amide), 1226 (C-O) e 1023 cm-1 (O-CH3). The electronic spectra of the complexes [M(phen)(S-Cros)2] and [M(phen)(O-Cros)2] obtained in metanol, presented intraligand and intrametal bands, where in the ultraviolet region there are the bands of phenanthroline ligand, already the ligand S-Cros display a band at 304 nm, and the ligand O-Cros display a band at 285 nm. Additionally to these transitions, all complexes presented three d-d bands, because of the coordination environment of the complexes. Cyclic voltamograms of all complexes were obtained in TBAP dissolved in DMSO, presenting quasi reversible processes for both metals, for cobalt the processes are Co2+/Co1+ and Co3+/Co2+ and for Cu2+/Cu1+ for copper in the systems [M(phen)(S-Cros)2] and [M(phen)(O-Cros)2], besides there are oxireduction processes of the S-Cros and O-Cros ligands.